HOW TO MAKE BAGS.
The old-fashioned carpet bag (Fig. 1) is still unsurpassed by any, where rough wear is the principal thing to be studied. Such a bag, if constructed of good Brussels carpeting and unquestionable workmanship, will last a lifetime, provided always that a substantial frame is used.
FIG 1.—THE CARPET BAG.
Next in order comes the brief bag (Fig. 2), more extensively used than any other. For business purposes it is in great favor with bag users, being made in a variety of shapes, but all belonging to the same class. Here we have the shallow brief, deep brief, eclipse wide mouth, imperial wide mouth, excelsior, courier, and many others; but to know how to make one will be sufficient for all, the only difference being in the cut or style in which they are constructed.
FIG. 2.—THE BRIEF BAG.
The cricket bat bag (represented in Fig. 3) is made on the same principle throughout as the carpet bag.
FIG. 3.—THE CRICKET BAT BAG.
Frames and all necessary fittings required in making bags may be purchased of dealers.
Care must be observed in choosing all the pieces necessary for a bag from the same pattern carpet, otherwise it will present an unsightly appearance when completed. There may be some who would prefer American cloth; this is thoroughly waterproof, and has a good appearance for some time, but, like all articles of imitation, it has only cheapness to recommend it. If cloth is to be used (I mean American cloth), let it be the best that can be bought, that which is called "double-twill duck," if possible. As the making is the same whether cloth or carpet be used, it will be understood that the instructions for making apply to both.
The following tools, which are few and inexpensive, will be required: A pair of clams (Fig. 4), cost 1s. 6d.; knife (Fig. 5), 6d.; half dozen awl blades, ½d. each; three or four boxwood handles, 1½d. each; 3 foot rule, 1s.; hammer, 1s.; a packet of harness needles, size 4, cost 2½d. (these have blunt points); a bone (Fig. 6) will also be required for rubbing the stiffening into place, cost about 3d.; and a ball each of hemp and wax for making the sewing threads—hemp 2½d., wax ½d. For making holes in the bottom where the nails or studs are fixed, a large sewing-awl will be required; this will probably have to be bought at a saddler's; the other tools can all be obtained at any grindery and leather seller's.
FIG. 4—Pair of Clams. FIG. 5—Knife. FIG. 6—Bone Rubber. FIG. 7—Method of Measuring Registered Frame: A to A, Top of Sides; A to B, Top of Gussets. FIG. 8—Pattern of Bottom, Showing Place of Nails. FIG. 9—Side Pattern Folded. FIG. 10—Gusset Pattern Folded. FIG. 11—Pattern for Gusset Stiffening. FIG. 12—Handle, Showing Distance of Rings.
The awl blades mentioned above are of two kinds, and either may be used for this work. Those generally used are of a straight diagonal shape, making a perforation the shape of a diamond, <> ; the others are perfectly round, tapering gradually to a fine point. To fix them in the boxwood handles, place the blade in a vise, leaving the unpolished part above the jaws; hold the handle above this, and commence driving it down, taking care that the blade is penetrating the middle of the handle. Continue tapping the handle until the ferrule reaches the polished part of the blade; it will then be in far enough.
A good serviceable pair of clams may be made by taking two staves of a good-sized barrel, and cutting about 10 inches off the end of each. Screw together with three screws (as in Fig. 4), and shape the uppermost ends so that the outsides meet in a sharp ridge along the top; this will give a flat surface within the mouth, by which a hold of the work may be obtained. A two-inch screw will be long enough for the bottom, which must be turned in as tightly as possible; the others must not be less than 3 inches, as there will be a space of 1½ or two inches between the staves at the part where they are inserted. Screw these just tight enough to give a good sharp spring to the mouth of the clams when they are pressed open; this will insure the work being held firmly while being sewn. Sandpaper them over to give a smooth appearance, and these will be found as useful as bought ones.
A piece of basil leather will be required for the bottom and welts of the bag. This may be purchased at a leather seller's with the tools. Cut out the bottom first; the welts may be cut from any narrow pieces. These must be cut seven-eighths of an inch wide, then folded over, and lightly hammered down. This brings the two edges together, and when placed in position, they should lie evenly between the edges of the material. A piece of string may be laid in the welt to give it a fuller appearance if the leather is very thin.
The following dimensions of bags when made up will enable the maker to choose the most useful size:
No. 1, 16 by 14 inches; No. 2, 19 by 16 inches;
No. 3, 21 by 17 inches; No. 4, 24 by 18 inches.
The sizes of frames and parts when cut will be as follows:
| Frame. | Sides. | Bottom. | Gussets. |
| No. 1, 15 inches | 16½ by 15½ | 16½ by 5½ | 15½ by 5½ |
| No. 2, 18 inches | 19½ by 17½ | 19½ by 6 | 17 by 6 |
| No. 3, 20 inches | 21½ by 18½ | 21½ by 6½ | 18½ by 6½ |
| No. 4, 23 inches | 24½ by 19½ | 24½ by 6½ | 19½ by 6½ |
Taking No. 1, 16½ inches will be the length of sides and 15½ inches the depth. The gussets are also 15½ deep, the width being 5½, the same as the bottom. Take 1½ inches from the depth of these to allow for covering the frame, and ½ inch from the length to allow for the seams, and we have a bag 16 inches long by 14 inches deep.
And now to commence. Arrange the pieces of carpet on the board, and mark off the size of each part required with a piece of chalk or pipeclay. By cutting with the carpet, laying the right side up, we shall be able to see that the pattern of it will be in the same direction on both sides of the bag when made up. We next take the ball of hemp, and by pushing the finger through the hole in the center of it, drive out the end. To use the hemp from the inside is much the best way, because the ball will stand perfectly still, whereas, if started from the outside, it will be darting in all directions about the floor of the workroom, and entwining itself around any obstacle which lies there, unless it is placed securely in a box and drawn out through a hole in the center of lid.
A hook must be fixed in some convenient place to make the waxends on, or, as they are called in the trade, "threads," which term it will be as well to call them by here; thus a four-cord thread means a thread or waxend containing four strands of hemp, a six-cord contains six strands, and so on. One of the greatest difficulties for the amateur is to produce a well-formed thread. He generally finds it thicker a few inches from the point than at any other part. These are known in the trade as bull-necked threads; and as the mechanic finds it difficult to use them when his employer starts a new apprentice and gives him this job for the men, I must impress on the worker here the necessity of making them as perfect as possible. It would be as well if a little practice was given at breaking the hemp in the way which produces good points. Better waste a few yards of hemp than be compelled to abandon a thread after making only a few stitches with it.
Gripe the hemp firmly between the thumb and forefinger of the left hand, leaving about eight or nine inches hanging loosely down; lay this over the thigh of the right leg, and with the right hand rub it in a downward direction, which will cause the twisted strand to loosen. One good stroke should be sufficient; if not, it must be repeated until the fibers forming the strand are quite loosened. By holding it close to the end with the right hand, and giving it a jerk with the left, the fibers will break, and the ends of the strands formed in this way are placed at a little distance one above another, which, when twisted, form a smooth, tapering point.
To cast off a thread the proper way is to stand at a distance of about three feet from the hook previously mentioned, and by holding the end of the hemp in the left hand, pass it over the hook and bring it down with the right, then holding with the left and breaking as above. When sufficient strands to form the thread have been broken off, carefully examine the points to see that they taper properly, and have no lumps in them. Rub the wax up and down a few times, so that the thread may be properly waxed on that portion which will be inside when twisted. Hold the two ends in the left hand, and with the right roll each end separately down the right leg a sufficient number of times to twist the thread throughout. Judgment will be required in this operation, or the thread will be a constant source of trouble if it is over-twisted. Wax it again, and then it is ready for use. See that the points are well waxed, then take a needle and pass the point of the thread through the eye until it nearly reaches that part which would stop its progress.
It must now be turned down on to the thicker portion and carefully twisted. Smooth it down, then take the other end of thread and another needle, and fasten it on in the same way. In selecting the awl to be used, do not take a very large one. The hole should be just large enough for the thread to require a slight pull to get it through.
To commence sewing take one side and a gusset and place them evenly together, the right side of the material being inside, and fix them in the clams. Slip the welt as previously described between the edges, and pass the awl through the lot. Drive it perfectly straight, as upon this chiefly depends a nice seam when turned. Draw out the awl, and by following the point, pass up the bottom needle with the left hand. This should be taken by the thumb and forefinger of the right hand and the thread pulled through half its length, so forming a thread of equal length on each side. Make another hole with the awl about one-third of an inch from the first. This gives the length of stitch. Pass up the bottom needle as before into the right hand, the top needle descending to the bottom immediately after. Take hold of this with the left hand and pull through the threads simultaneously top and bottom, until the extremity on each side lies on and forms the stitch. Be careful that in pulling in the latter part each thread closes at the same time, thereby preventing a crooked seam. Repeat until the seam is finished, then take the other gusset and place in position. Sew this, then take the other side of bag and sew to the gussets. You will then have something in the shape of a bag, minus the bottom. Take this next, and fix each corner to one of the seams previously made, and stitch it carefully round, placing a welt in as before. At the end of each seam a stitch or two back should be taken or the thread tied over to prevent it opening.
The outside of the bag being inward, it must now be turned previous to stiffening and framing. The turning is done by placing the bag over the left arm, and with the right hand commence pushing in one of the corners, then the opposite one until that end is reversed. Then serve the other end in a similar manner, and smooth each seam along.
We now take a piece of stout millboard (an old ledger book cover will do if large enough), or, if purchased with the frame, ask for a two pound board: this will cost about 4d., and be sufficient for several bags. Cut it quarter of an inch less than the bottom all round, and see that it fits before gluing it in. To do this, place one end within the seams at one end of the bag, and by lifting it in the middle press in the other, when the stiffening will lie within the four seams at the bottom. Having fitted it satisfactorily, take it out again and glue it well with some good hot glue. This must be neither too thick nor too thin. The best way to prepare it is to lay some glue in cold water for twelve hours. It will absorb sufficient water in that time, and can be boiled up without any further preparation. The quicker it is fixed after the glue is put on the better. A brush similar to a paint brush will be the best to apply it with, and need not cost more than 6d. After the gluing, lay it aside for a few hours to allow it to thoroughly set, during which time the making of the handles can be proceeded with. On some bought bags these are very common, and seldom last more than a few months; the usual plan being to take a piece of rope about the size of a clothes line and roll a piece of brown paper round it, covering it afterward with a piece of basil leather.
Procure two pieces of brown harness leather—the shoulder of the hide is most suitable—from a saddler, 11 inches long by 1-1/8 inches wide, round the four ends, and make a compass mark 1/8 of an inch from the edge all round for the stitching. Take a piece of line as above, and place within the leather, which most likely will have to be damped to make it draw round easier. Leave 1½ inches from each end for sewing to the bag, the line also being so much less than the full length of the handles. Having sewn them, flatten the ends and bend the handles into a semicircular shape, and leave them to dry.
By this time the glue holding the stiffening to the bottom of the bag will be set, so the next move will be to put in the studs or nails. Take the largest size awl and make five punctures through the bottom, about three-quarters of an inch from each corner and one in the center, as in Fig 8; push the nails through and turn down each of the two claws in an opposite direction, tap them with a hammer to make them lie closer, and also to prevent them from becoming loose. This done, we next take the frame and remove the key-plate from it.
Fold the sides of the bag well over the frame, so that the stitching will get a good hold of the part that goes inside. Put a stitch through at each corner to hold it, and see that it sets perfectly true on the frame. A space is left between the two plates of iron forming the frame, which allows of the bag being sewn through it. Fix the key-plate by riveting inside. Sew the bag from one corner of frame to the other corner on each side, leaving the gussets unstitched. It is now ready for the lining. Let this be good, as it will greatly add to the durability of the bag if strong. Coarse linen at 8d. to 10d. per yard is the best material for this purpose. The sides and bottom may be cut in one piece; the length of this will be twice the depth of one side of carpet (less the part which folds over the frame) and the width of the bottom. The width of this piece throughout to be a half inch less than the outsides were cut. The gusset lining will want to be the same width as the gusset, but an inch less in length will do. The seams of the lining may be stitched with an ordinary household sewing machine if good thread is used. When made, place the lining inside the bag, see that it is well down at the bottom, turn in the top edge all round to the required size, and fix in as follows: Take a long carpet needle and a length of thread, pass the needle through the lining at the folded ridge and bring it up again through the same at a distance of an inch or so. This forms a stitch within the lining; pass the needle through one of the stitches made in sewing in the frame and repeat as before, carefully observing that the lining falls into its proper place as it is being sewn in. Continue in this way until the two sides are done, leaving only the gussets and gusset lining to be united. This is done by folding the edges inward and sewing them together, the frame joints moving freely between the gussets and lining. We have now only the handles to put on and it is complete. Sew these on with a five cord thread well waxed. To protect the lock against being unduly strained when filled, a strap and buckle may be put on between the handles and each end of the frame, as in Fig. 3.
Next in order is the cricket bat bag, which should always be comprised in the outfit of the amateur cricketer, as well as of the professional. In making this we follow the instructions given for the carpet bag. It may be made either of carpet, tan-canvas, or leather, the latter, of course, being the strongest and most expensive. Carpet will not require to be described, but a brief description of tan-canvas and leather may be of service to the amateur in assisting him to choose something for himself.
Tan-canvas, as used for bags and portmanteaux, is a strong, coarse material of a brown color; it wears well, and has one advantage over carpet—it is thoroughly waterproof.
Leather is, of course, superior to carpet or canvas, but there are a few tricks in its manufacture which it may not be out of place here to mention as a caution to the amateur that the old saying, "There's nothing like leather," is a thing of the past where the general appearance of an article is meant. The genius of the inventor has produced machinery which gives to paper, linen, and other stuffs the appearance of the genuine article, whereas it does not contain one particle of it. At one time, when a hide of leather was required to be of the same thickness all over it, the currier would work at the flesh of the skin with a shaving knife, gradually scraping the thick parts away until it was reduced to the required substance. Now it is done in a few minutes. The hide is passed whole between the rollers of a splitting machine against the sharp edge of a knife, which reaches from one side of the machine to the other, a distance of 10 or 12 feet. This knife is so gauged that any thickness can be taken off at one operation, the part taken off resembling the hide in size and shape. The top or grain of the hide is then dressed and finished off brown, if for brown hides; or, if to be used for enameled hides, they are dyed and japanned. These are called either brown or enameled cow-hides, according as they are finished off, and are used for all the best class of Gladstone, brief, and other bags. The bottom or fleshing of the hide is also dyed and japanned, and when finished, exactly resembles in appearance the hide itself, and is very difficult for the novice to tell when made up into bags or any other article. These are called splits, and having had the best part of the skin taken from them, do not wear one-fourth the time the grain will. The black enamel soon chips off, which gives them a worn-out appearance.
To make a bag 36 inches by 12 inches by 8 inches requires a frame 36 inches long, the sides 36½ inches by 14 inches, gussets 14 inches by 8½ inches, bottom 36½ inches by 8 inches. The lining will be 36 inches by 12 inches for the sides, gussets 13 inches by 8 inches, bottom 36 inches by 8 inches. For the handles two pieces of leather 12 inches by 2 inches. The straps and chapes are sewn on quite close to the frame, straps 10 inches long by 1 inch, chapes 4½ inches by 1 inch. Cut a slit in the middle of the chape for the buckle tongue to go through, and pare the under side at the end so that it is not too lumpy when sewn on to the bag. Cut two loops 3 inches long by ¾ inch wide for the points of straps to go through.
The brief bag must be made of leather, and as there is the same amount of work in making it, whether it be of split or hide, it will be sure to give greater satisfaction if the latter is chosen. The manufacture of this bag differs considerably from the others. The sides and gussets in the carpet bag are cut straight from top to bottom, but in the brief bag they must be shaped to fit the frame, and give it a more comely appearance. The frame, as before described, is quite different. The way to commence with this bag is to open the frame as in Fig. 7, so that it will lie perfectly flat upon the bench. With the rule measure it carefully between the corners, A, A, and again at A, B. The distance between A and B being less when the frame is open than when closed, an additional ½ inch must be added to allow the gusset to bend freely round the hinge. Having correctly taken these measurements, get a sheet of brown paper and fold it in the middle; the reason for this is to allow of each side of the pattern taking the same curve at the swelled part. Cut the pattern for the sides first by ascertaining half the distance, A, A, and marking it on to the edge of the paper, measuring from the folded edge toward the ends. Next mark on the folded edge the depth you intend the bag to be, allowing in this, as in the carpet bag, 1½ inches for covering the frame. The depths of brief bags vary so much that I will give these only as a guide, leaving my readers to add or reduce as their fancy guides them; but if they should strictly adhere to these given below, I am certain they will find them very useful sizes.
For a 12 inch frame cut the sides and gussets 10½ inches in depth; when made up, these will be 9 inches from the frame to the bottom. For a 14 inch frame add 1 inch, and for a 16 inch add 2 inches. This will make these 10 inches and 11 inches in depth respectively when made up, and either of these will be found a very useful bag for many purposes. The width of the bottoms to be cut 5 inches, 5½ inches, and 6 inches, the 5 inch, of course, for the 12 inch bag, the 5½ inch for the 14 inch, and the 6 inch for the 16 inch. The depth having been decided upon, and marked on the folded edge of the paper, make another mark the same distance from the edge at the first mark, H. The bottom of the sides being 1 inch longer than the top, add ½ inch to the measurement of the top of pattern when the bottom part is marked off at J L. Draw a curved line between H L, as in Fig. 9, and cut through the two thicknesses of paper at one time, keeping them well together to insure them being alike. The gusset pattern may be cut in the same way, D to D, Fig. 10, being half the distance of A B, Fig. 7, and the ½ inch added for going round the joint; E E, the swelled part, which bends into the bag when the frame is closed, and also allows it to open perfectly square; F F is half the width of the bottom of gusset. A pattern for the bottom of the bag may be made by folding a piece of paper each way to get the length and width; make a small hole through the four thicknesses, open it and mark it from hole to hole, using the rule as a guide. This will be found to be perfectly accurate.
To cut out the bag, lay the leather on the bench, enameled side downward, and see that the patterns lie on it so the creases will run from the top to bottom of the bag when made. The sides must be taken first, and as they are more exposed than any other part, they should be taken from the best part of the hide. Take the gussets next, then the bottom. The welts are taken from the cuttings which are left. To make the handle, glue a lot of odd pieces together about 6½ inches long, ½ inch wide, and the same thickness, and when dry pare the edges away until it is perfectly round and slightly tapering toward each end. It is then divided and glued top and bottom to a strip of good leather cut to shape, Fig. 12, which is passed through the rings at each end, and turned back to form a shape. Put a few stitches through close to the rings before the fittings are glued on, and cover with a piece of cow-hide long enough to go through the two rings and along the under side, then stitch it. Trim and dye the edges, rubbing them afterward with a piece of cloth to produce a polish. Before making the handle, the plates must be on the rings, or it will prove a difficult job to get them on afterward.
The stiffening for the bottom will be cut as if for a carpet bag. Fig. 11 represents the stiffening for the gussets, and is cut from a board half the thickness of that used for the bottom.
The linings may be cut from the outside patterns by reducing them the 1½ inches, allowed for covering the frame, and 1/8 inch for each welt. A lining of scarlet or blue roan greatly adds to the appearance and durability of a bag. A skin large enough for a 14 inch or 16 inch will cost about 3s.
Cow-hide for the outside is sold at 1s. 8d. per square foot, but the leather sellers frequently have pieces large enough for making a bag which they will sell at a slight reduction, and which answers this purpose as well as cutting a hide. In seaming the bag, take care not to wrinkle it in the clams. The welts in this must reach only to the frame, the same as in the carpet bag; the rest of the seam must be neatly closed and rubbed down, so that it will not be lumpy on the frame. Before turning the bag warm it before the fire, especially if it is cold weather. Glue in the bottom stiffening first, and then the gussets, rubbing them well down with the bone. When these are set, prepare for the operation of framing. Fold one of the sides to get the middle of it, cut a hole for the lock barrel about 1¼ inches from the edge, and press it over. Be careful not to cut it too large or the hole will show. Pierce a hole through the leather for the lock plate, press this tightly on the frame, and clinch the clams underneath, to hold it securely. Make holes for the handle plates and fasten them on in a similar manner. Two slits must be cut near the middle of the other side of bag, about ¾ inch from the edge, for the hasp to go through. This bag must be sewn to the frame all round, and care must be taken that a sufficient fullness is allowed in the middle of the gusset to enable it to close easily round the joints of the frame. A thumbpiece must be sewn on the bag at the hasp to open it by. The lining of this bag is sewn through the frame all round in the same manner as the side linings of the carpet bag.
I hope my readers will not think that I have gone too much into details. It is in small things that so many failures take place. As it is much easier to do anything when you are shown than when so much has to be guessed, it is my desire to make the road for beginners as smooth as possible, which must be my excuse if any is required. It is as well that those who intend to turn their attention to working in leather should begin by making a bag; the experience gained in cutting, fitting, putting together, and finishing will be useful when larger and more difficult pieces of work are undertaken.—Amateur Mechanics.
MOLASSES, HOW MADE.
The New England Grocer says that the manufacture of molasses is really the manufacture of sugar up to a certain stage, for molasses is the uncrystallized sirup produced in the making of sugar. The methods of manufacture in the West Indies vary very considerably. In the interior and on the smaller plantations it is made by a very primitive process, while on the larger plantations all the appliances of modern science and ingenuity are brought to bear. Each planter makes his own sugar. It is then carried to the sea coast and sold to the exporters, by whom it is shipped to this country. The quality and grade of the molasses varies with each plantation. Two plantations side by side may produce entirely different grades. This is owing to the soil, which in Porto Rico and other localities in the West Indies seems to change with almost every acre. The cane from which the sugar and molasses is made is planted by laying several pieces of it in holes or trenches. The pieces are then covered with earth to the depth of two or three inches. In about two weeks sprouts appear above the surface. Then more earth is put in, and as the sprouts grow, earth is added until in three or four months the holes are filled up. The planting is done from August to November, and the cutting progresses throughout the greater part of the year. The cane grows to a height of seven or eight feet, in joints each about a foot long.
When the cane is in proper condition for cutting, as shown by its appearance, an army of workmen take possession of the field. Each is armed with a long, broad knife, like a butcher's cleaver. They move down the lines of cane like an army, and while the cutting is going on the fields present an interesting sight, the sword-like knives flashing in the sun, the 300 or 400 laborers, the carpet of cut cane, the long line of moving carts, and the sea of standing cane, sometimes extending for miles and miles, stirred by the breeze into waves of undulating green. The laborers employed on these plantations are largely negroes and Chinese coolies. When the cane is ripe, they proceed to the field, each armed with a matchet. Spreading over the plantation, they commence the cutting of the cane, first by one cut at the top, which takes off the long leaves and that part which is worthless, except as fodder for the cattle. A second cut is then given as near the root as possible, as the nearer the ground the richer the cane is in juice. The cut cane is allowed to fall carelessly to the ground.
Other workmen come with carts, pick it up, tie it in bundles and carry it to the mill. The cutting of the cane is so adjusted as to keep pace with the action of the mill, so that both are always at work. Two gangs of men are frequently employed, and work goes on far into the night during the season, which lasts the greater part of the year.
As before stated, some of the methods of manufacture are very simple. In the simplest form, the sugar cane is crushed in a mortar. The juice thus extracted is boiled in common open pans. After boiling a certain length of time, it becomes a dark colored, soft, viscid mass. The uncrystallized sirup is expressed by putting the whole into cloth bags and subjecting them to pressure. This is molasses in a crude state. It is further purified by reboiling it with an addition of an alkaline solution and a quantity of milk. When this has continued until scum no longer arises, it is evaporated and then transferred to earthen jars. After it has been left for a few days to granulate, holes in the bottom of the jars are unstopped, and the molasses drains off into vessels placed to receive it. Another process of extracting molasses is as follows: By various processes of boiling and straining, the juice is brought to a state where it is a soft mass of crystals, embedded in a thick, but uncrystallized, fluid. The separation of this fluid is the next process, and is perfected in the curing house, so called. This is a large building, with a cellar which forms the molasses reservoir. Over this reservoir is an open framework of joists, upon which stands a number of empty potting casks. Each of these has eight or ten holes bored through the bottom, and in each hole is placed the stalk of a plantain leaf. The soft, concrete mass of sugar is removed from the cooling pans in which it has been brought from the boilers and placed in the casks. The molasses then gradually drains from the crystallized portion into the reservoir below, percolating through the spongy plantain stalks.
On the larger plantations, machinery of very elaborate description is used, and the most advanced processes known to science are employed in the manufacture. The principle is, however, the same as has been seen in the account of the simpler processes. On these larger plantations there are extensive buildings, quarters for workmen, steam engines, and all the necessary adjuncts of advanced manufacturing science. In the sugar mills the cut cane is carried in carts to the mill. It is then thrown by hand upon an endless flexible conductor which carries the cane between heavy crushers. The great jaws of the crushers press the cane into pulp, when it is thrown aside automatically to be carted away and used as a fertilizer. The juice runs off in the channels of the conductor into huge pans. The juice is now of a dull gray color and of a sweet, pleasant taste, and is known as guarapo. It must be clarified at once, for it is of so fermentable a nature that in the climate of Porto Rico it will run into fermentation inside of half an hour if the process of clarifying is not commenced. The pans into which the juice is conducted are pierced like a colander. The liquor runs through, leaving the refuse matter behind. It is then forced into tanks by a pump and run to the clarifiers, which are large kettles heated by steam. Lime is used to assist the clarification. It is then filtered into vats filled with bone black. The filtering is repeated until the juice changes color, when it is conveyed to the vacuum pans. It has now become a thick sirup. It is then pumped into the sirup clarifiers, skimmed, and again run through bone black, and finally is conducted into another kettle, where it is allowed to crystallize. The sirup that fails to crystallize is molasses, and it is here that we catch up with what we started after. To extract the molasses from the crystallized mass of sugar, we must go to the purging house. This is similar to the building spoken of in connection with the simpler process. It is of two stories. The upper floor is merely a series of strong frames with apertures for funnel-shaped cylinders. The sugar is brought into the purging house in great pans, which are placed over the funnels. The pans are pierced with holes through which the molasses drains off into troughs which are underneath the floor, all running to a main trough. From thence the molasses runs into vats, called bocoyes, each of which holds from 1,200 to 1,500 gallons. The hogsheads in which the molasses is brought to this country are manufactured principally in Philadelphia and taken to the West Indies. They are placed in the hold of the vessel and the molasses pumped into them. The government standard for molasses is 56 degrees polarization. When not above that test, the duty is four cents per gallon. Above it the duty is eight cents. This tends to keep molasses pure, as the addition of glucose increases the quantity of sugar and therefore of the polarization, and would make necessary the payment of increased duties. The adulteration of molasses is therefore largely if not wholly done after it is out of bond and in the hands of the jobber.
PRIMITIVE IRON MANUFACTURE.
We are indebted for the illustrations and the particulars to Dr. Percy's invaluable book on iron and steel (probably it is not saying too much to describe it as the best work on the subject ever written).
SECTION OF INDIAN BLAST FURNACE AND BLOWING MACHINE.
Fig. 1 shows a sectional elevation, and Fig. 2 shows a plan of furnace and bellows and tuyeres, indeed, an entire ironworks plant used in India, not only now, but, so far as we can gather, from time immemorial. The two figures give a sufficiently clear idea of the form of furnace used in Lower Bengal, in which portion of our Indian empire there are entire villages exclusively inhabited by iron smelters, who, sad to relate, are distinguished from the agricultural villages surrounding them by their filth, poverty, and generally degraded condition. There are whole tribes in India who have no other occupation than iron smelting. They, of course, sink no shafts and open no mines, and are not permanent in any place. They simply remain in one place so long as plentiful supplies of ore and wood are obtainable in the immediate vicinity. In many cases the villages formerly inhabited by them have passed out of existence, but the waste, or rather wasted products, of their operations remain.
The furnace shown in Figs. 1 and 2 is built of the sandy soil of the district, moistened and kneaded and generally strengthened by a sort of skeleton of strips of flexible wood. In form it varies from a cylinder, more or less circular, diverging into a tolerably acute cone, the walls being about 3 in. thick. The height is generally about 3 ft. and the mean internal diameter about 1 ft., but all these dimensions vary with different workmen and in different localities. There are two apertures at the base of the furnace; one in front, about 1 ft. in height, and rather less in width than the internal diameter of the furnace, through which, when the smelting of one charge is finished, the resulting mass of spongy iron is extracted, and which during the smelting is well plastered up, the small conical tuyere being inserted at the bottom. This tuyere is usually made of the same material as the furnace—namely, of a sandy soil; worked by hand into the required form and sun-dried; but sometimes no other tuyere is employed than a lump of moist clay with a hole in it, into which the bamboo pipes communicating with the bellows are inserted. The other aperture is smaller, and placed at one side of the furnace, and chiefly below the ground, forming a communication between the bottom of the furnace chamber and a small trench into which the slag flows and filters out through a small pile of charcoal. It is this slag being found in places where iron is not now made that shows that iron smelting was an occupation there, perhaps many centuries before.
The inclined tray shown at the top of the furnace on Fig. 1 is made of the same material as the furnace itself, and when kneaded into shape is supported on a wooden framework. On it is piled a supply of charcoal, which is raked into the furnace when required.
The blowing apparatus is singularly ingenious, and is certainly as economical of manual labor as a blowing arrangement depending on manual labor well can be. A section of the bellows forms the portion to the right of Fig. 1, showing tuyere forming the connection between bellows and furnace. It consists of a circular segment of hard wood, rudely hollowed, and having a piece of buffalo hide with a small hole in its center tied over the top. Into this hole a strong cord is passed, with a small piece of wood attached to the end to keep it inside the bellows, while the other end is attached to a bent bamboo firmly fixed into the ground close by. This bamboo acts as a spring, drawing up the string, and consequently the leather cover of the bellows, to its utmost stretch, while air enters through the central hole. When thus filled, a man places his foot on the hide, closing the central hole with his heel, and then throwing the whole weight of his body on to that foot, he depresses the hide, and drives the air out through a bamboo tube inserted in the side and communicating with the furnace. At the same time he pulls down the bamboo with the arm of that side. Two such bellows are placed side by side, a thin bamboo tube attached to each, and both entering the one tuyere; and so by jumping on each bellows alternately, the workman keeps up a continuous blast.
Fig. 2.—PLAN OF INDIAN BLAST FURNACE AND BLOWING MACHINE.
The Figs. 1 and 2 are taken from sketches, and the description from particulars, by Mr. Blandford, who was for some years on the Geological Survey of India, and had exceptional opportunities in his journeyings of observing the customs and occupations of the Indian iron smelters. The blowing machine is an especially wonderful and effective machine, and was first described and illustrated by Mr. Robert Rose, in a Calcutta publication, more than half a century ago. He also had seen it used in iron making in India.—Colliery Guardian.
WOOD OIL.
Wood oil is now made on a large scale in Sweden from the refuse of timber cuttings and forest clearings, and from stumps and roots. Although it cannot well be burned in common lamps, on account of the heavy proportion of carbon it contains, it is said to furnish a satisfactory light in lamps specially made for it; and in its natural state it is the cheapest illuminating oil. There are some thirty factories engaged in its production, and they turn out about 40,000 liters of the oil daily. Turpentine, creosote, acetic acid, charcoal, coal-tar oils, etc., are also obtained from the same materials as the wood oil.
SOAP.
By HENRY LEFFMANN, M.D.
Although the use of soap dates from a rather remote period, the chemist is still living, at an advanced age, to whom we are indebted for a knowledge of its composition and mode of formation. Considerably more than a generation has elapsed since Chevreul announced these facts, but a full appreciation of the principles involved is scarcely realized outside of the circle of professional chemists. Learned medical and physiological writers often speak of glycerin as the "sweet principle of fats," or term fats compounds of fatty acids and glycerin. Indeed, there is little doubt that the great popularity of glycerin as an emollient arose from the view that it represented the essential base of the fats. With regard to soap, also, much erroneous and indistinct impression prevails. Its detergent action is sometimes supposed to be due to the free alkali, whereas a well-made soap is practically neutral.
A desire to secure either an increased detergent, cleansing, or other local effect has led in recent years to the introduction into soaps of a large number of substances, some of which have been chosen without much regard to their chemical relations to the soap itself. The result has been the enrichment of the materia medica with a collection of articles of which some are useful, and others worse than useless. The extension of the list of disinfectant and antiseptic agents and the increased importance of the agents, in surgery, have naturally suggested the plan of incorporating them with soaps, in which form they will be most convenient for application. Accordingly, the circulars of the manufacturing pharmacists have prominently displayed the advantages of various disinfecting soaps.
Among these is a so-called corrosive sublimate soap, of which several brands are on sale. One of these, containing one per cent. of corrosive sublimate, is put on the market in cakes weighing about sixteen hundred grains, and each cake, therefore, contains sixteen grains of the drug—a rather large quantity, perhaps, when it is remembered that four grains is a fatal dose. Fortunately, however, for the prevention of accidents, but unfortunately for the therapeutic value of the soap, a decomposition of the sublimate occurs as soon as it is incorporated in the soap mass, by which an insoluble mercurial soap is formed. This change takes place independently of the alkali used in the soap; in fact, as mentioned above, a well-made soap contains no appreciable amount of free alkali, but is due to the action of the fat acids. Corrosive sublimate is incompatible with any ordinary soap mass, and this incompatibility includes not only other soluble mercurial salts, but also almost all the mineral antiseptics, such as zinc chloride, copper sulphate, iron salts. Some of the preparations of arsenic may, however, be incorporated with soap without decomposition.
Such being the chemical facts, we must admit that no reliance can be placed in corrosive sublimate soaps as germicide agents. It must not be supposed that this incompatibility interferes with the use of these soaps for general therapeutic purposes. It is only the specific germicide value which is destroyed. Since the fats used in soap manufacture yield oleic acid, we will have a certain amount of mercuric oleates formed together with stearate and other salts, and for purposes of inunction these salts might be efficient. Still the physician would prefer, doubtless, to use the specially prepared mercurial.
In producing, therefore, a disinfecting soap, being debarred from using the metallic germicides, we are fortunate in the possession of a number of efficient agents, organic in character, which may be used without interference in soaps.
Among these are thymol, naphthol, oil of eucalyptus, carbolates, and salicylates. There is no chemical incompatibility of these with soap, and as they are somewhat less active, weight for weight, than corrosive sublimate, they are capable of use in larger quantities with less danger, and can thus be made equally efficacious.
It is in this direction, therefore, that we must look for the production of a safe and reliable antiseptic soap.
There is not much exact knowledge as to the usefulness of such additions to soap as borax and glycerin. They are frequently added, and highly spoken of in advertisements. Borax is a mild alkaline body, and as a detergent is probably equivalent to a slight excess of caustic soda. Glycerin, although originally considered an emollient, probably on account of its source and physical properties, is in reality, to some skins at least, a slight irritant. It is, in fact, an alcohol, not a fat. It does not pre-exist in fats, but is formed when the fat is decomposed by alkali or steam.
In ordinary cases, soap owes its detergent effect to a decomposition which occurs when it is put in water.
A perfectly neutral soap, that is, one which contains the exact proportion of alkali and fat acid, will, when placed in cold water, decompose into two portions, one containing an excess of the acid, the other an excess of alkali. The latter dissolves, and gives a slightly alkaline solution; the former precipitates, and gives the peculiar turbidity constituting "suds." These reactions must be kept in mind in determining the effect of the addition of any special substance to the soap.—The Polyclinic.
OPTICAL ERRORS AND HUMAN MISTAKES.[1]
By ERNST GUNDLACH.
I wish to call attention to a few mistakes that are quite commonly made by microscopists and writers in stating the result of their optical tests of microscope objectives.
If the image of an object as seen in the microscope appears to be unusually distorted and indistinct toward the edge of the field, and satisfactory definition is limited to a small portion of the center, the cause is often attributed to the spherical aberration of the objective, while really this phenomenon has nothing to do with that optical defect of the objective, if any exists, but is caused by a lack of optical symmetry. If a perfectly symmetrical microscope objective could be constructed, then, with any good eye-piece, it would make no difference to the definition of the object were it placed either in the center or at the edge of the field, even if the objective had considerable spherical aberration. But, unfortunately, our most symmetrical objectives, the low powers, leave much to be desired in this respect, while our wide angle, high powers are very far from symmetrical perfection.
There are two causes of this defect in the latter objectives, one being the extreme wideness of their angular apertures, and the other the great difference in the distances of the object and the image from the optical center of the objectives.
Another mistake is often made in regard to the cause of certain prismatic colors that are sometimes, in a striking degree, produced by otherwise good objectives. According to the nature of these colors, whether yellow or blue, green or indigo, they are generally regarded as evidences of either chromatic over or under correction of the objective. Of course the presence of either of these defects is certainly and correctly indicated by the appearance of one or the other of the colors, under certain circumstances; but the simple visibility of prismatic color is by no means a reliable indication of over or under correction of color, and, indeed, to the honor of our opticians, it may be stated that very few objectives are made that cannot justly be called achromatic in the general sense of the term. By far the most common causes of prismatic color, in otherwise carefully constructed objectives, are the so-called chromatic aberrations of second or higher order. Every achromatic lens which is, as it should be, at its best at about two-thirds of its aperture, is inside of this ring or zone, toward the center slightly under and outside, toward the edge, slightly over corrected. This defect is the greater, the less the difference of the dispersive powers of the two glasses used in the construction of the lens, for a given proportion of their refractive indexes, and therefore the degree of visibility of the colors of the aberrations of the second order depends greatly on the nature of the glass employed in the construction of the lens.
This defect may be corrected by a suitable combination of two or more lenses, though not without again having similarly, as in the correction of the first color, some faint remnants of color, the aberrations of third or still higher order. But even the correction of the third or still higher order may, if the angular aperture is very wide, leave quite visible and disturbing remnants of color.
Another and not uncommon explanation of the cause of this unwelcome color, though not so serious and damaging a charge to the maker of the objectives, is its attribution to the so-called "secondary spectrum." This error, like that previously mentioned, is certainly indicated by the appearance of certain colors under certain conditions, but being, as a rule, one of the least defects of even our best objectives in most cases, it is probably not the true source of the disturbance.
The secondary spectrum is very commonly confounded with the chromatic aberration of higher order. While the latter is produced by imperfections in the form of the lens, the former is due to an imperfection of the optical qualities of the material from which the lens is constructed, the crown and flint glass.
A glass prism of any angle will project upon a white surface a spectrum of any length, according to the arrangement of the light source, the screen, and the prism. So with two prisms of the same kind of glass, but of different angles, two spectra can be produced of exactly equal length, so that if one is brought over the other, with the corresponding colors in line, they will appear as one spectrum. But if one of the prisms is made of crown and the other of flint glass, then their spectra cannot be arranged so that all their corresponding colors would be in line, for the proportional distances of the different colors differ in the two spectra. If two colors of the spectra are, by suitable arrangement, brought exactly in line, then the others will be out. The two spectra do not coincide, and the result, if an achromatic lens be made of these glasses, must be a remnant of color which cannot be neutralized. This remnant is the secondary spectrum.
Although this peculiar disharmony in the dispersive powers of the two glasses, crown and flint, was discovered almost immediately after achromatism was invented, it was only recently that the first successful attempts were made to produce different glasses, which, possessing the other requirements for achromatic objectives, would produce coincident spectra, or nearer so than the ordinary crown and flint glass do. It was about twelve years ago, if my memory serves me, when I learned that a well-known English firm, engaged in the manufacture of optical glass, had brought out some new glass possessed of the desired qualities, and a little later I received a circular describing the glass. But at the same time I learned that the new glass was very soft and difficult to polish, and also that it had to be protected from the atmosphere, and further, that an English optician had failed to construct an improved telescope objective from it. I had ordered some samples of the glass, but never received any.
A few months ago, news from Europe reached this country that another and seemingly more successful attempt had been made to produce glass that would leave no secondary spectrum, and that Dr. Zeiss, the famous Jena optician, had constructed some new improved objectives from it. But the somewhat meager description of these objectives, as given by an English microscopist, did not seem fit to excite much enthusiasm here as to their superiority over what had already been done in this country. Besides this, the report said that the new objectives were five system, and also that extra eye-pieces had to be used with them. I confess I am much inclined to attribute the optical improvement, which, according to Dr. Abbe's own remark, is very little, more to the fact that the objectives are five system than to the new glass used in their construction.
After a close study of a descriptive list of the new glass, received a week or two ago from the manufacturers, I find, to my great regret, that this new glass seems to suffer from a similar weakness to that made by the English firm twelve years ago; as all the numbers of the list pointed out by the makers as having a greatly reduced secondary spectrum are accompanied with the special remark "to be protected." Furthermore, from a comparison of the dispersive and refractive powers of these glasses, as given in the list, I find that objectives constructed from them will leave so great aberrations of higher order, both spherical and chromatic, that the gain by the reduction of the secondary spectrum would be greatly overbalanced.
In conclusion, I wish to say that while I would beware of underestimating the great scientific and practical value of the endeavor of the new German glass makers to produce improved optical glass, and the great benefit accruing to opticians and all others interested in the use of optical instruments, I think it wise not to overestimate the real value of the defects of the common crown and flint glass, which I have sought to explain in this paper. And, for myself, I prefer to fight the more serious defects first, and when its time has come I will see what can be done with the secondary spectrum.
Read before the American Association, Buffalo, August, 1886.
PROBABLE ISOLATION OF FLUORINE. DECOMPOSITION OF HYDROFLUORIC ACID BY AN ELECTRIC CURRENT.
By M.H. MOISSAN.
In a former memoir[1] we showed that it was possible to decompose anhydrous hydrofluoric acid by the action of an electric current. At the negative pole hydrogen collects; at the positive pole a gaseous body is disengaged, having novel properties. The experiment was performed in a platinum U tube, closed by stoppers of fluorite, and having at the upper part of each branch a small delivery tube, also of platinum. Through the stopper passes a platinum rod, which acts as electrode. The metal employed for the positive pole is an alloy containing 10 per cent. of iridium.
To obtain pure anhydrous hydrofluoric acid, we begin by preparing fluorhydrate of fluoride of potassium, taking all the precautions pointed out by M. Fremy. When the salt is obtained pure, it is dried on a water bath at 100°, and the platinum capsule containing it is then placed in a vacuum in the presence of concentrated sulphuric acid, and two or three sticks of potash fused in a silver crucible. The acid and potash are renewed every morning for a fortnight, and the vacuum is kept at 2 cm. of mercury. Care must be taken during this desiccation to pulverize the salt every day in an iron mortar, so as to renew the surface. When the fluorhydrate contains no more water it falls to powder, and is then fit to serve for the preparation of fluoric acid; the fluorhydrate of fluoride of potassium, if well prepared, is much less deliquescent than the fluoride.
When the fluoride is quite dry, it is quickly introduced into a platinum alembic, which has just been dried by heating it to redness. The whole is kept at a gentle temperature for an hour or an hour and a half, so as to allow the decomposition to commence very slowly; the first portions of acid which come over are rejected as they carry with them traces of water remaining in the salt. The platinum receiver is then attached, and the heat increased, allowing the decomposition to proceed with a certain degree of slowness. The receiver is then surrounded with a mixture of ice and salt, and from this moment all the hydrofluoric acid is condensed as a limpid liquid, boiling at 19.5°, very hygroscopic, and, as is well known, giving abundant fumes in presence of the atmospheric moisture.
During this operation the platinum U tube, dried with the greatest care, has been fixed with a cork in a cylindrical glass vessel surrounded with chloride of methyl. Up to the moment of introducing the hydrofluoric acid, the leading tubes are attached to drying tubes containing fused caustic potash. To introduce the hydrochloric acid into the apparatus, it may be absorbed through one of the lateral tubes in the receiver in which it is condensed.
In some experiments we have directly condensed the hydrofluoric acid in the U tube surrounded with chloride of methyl; but in this case care must be taken that the tubes are not clogged up by small quantities of fluoride carried over, which would infallibly lead to an explosion and projections, which are always dangerous with so corrosive a liquid.
When we have introduced in advance in the small platinum apparatus a determined amount of hydrofluoric acid cooled with chloride of methyl, in tranquil ebullition at a temperature of -23°, the current of 20 cells of Bunsen large size, arranged in series, is passed through by means of the electrodes. An amperemeter in the circuit admits of the intensity of the current being observed.
If the hydrofluoric acid contains a small quantity of water, either by accident or design, there is always disengaged at the positive pole ozone, which has no action on crystallized silicium. In proportion as the water contained in the acid is thus decomposed, it is seen by the amperemeter that the conductivity of the liquid rapidly decreases. With absolutely anhydrous hydrofluoric acid the current will no longer pass. In many of our experiments we have succeeded in obtaining an acid so anhydrous that a current of 25 amperes was entirely arrested.
To render the liquid conducting, we have added before each experiment a small quantity of dried and fused fluorhydrate of fluoride of potassium. In this case, decomposition proceeds in a continuous manner; we obtain at the negative pole hydrogen, and at the positive pole a regular disengagement of a colorless gas in which crystallized silicium in the cold burns with great brilliancy, becoming fluoride of silicium. This latter gas has been collected over mercury, and accurately characterized.
Deville's adamantine boron burns in the same manner, but with more difficulty, becoming fluoride or boron. The small quantity of carbon and aluminum which it contains impedes the combination. Arsenic and antimony in powder combine with this gaseous body with incandescence. Sulphur takes fire in it, and iodine combines with a pale flame, losing its color. We have already remarked that it decomposes cold water, producing ozone and hydrofluoric acid.
The metals are attacked with much less energy. This is due, we think, to the small quantity of metallic fluoride formed preventing the action being very deep. Iron and manganese in powder, slightly heated, burn with sparks. Organic bodies are violently attacked. A piece of cork placed near the end of the platinum tube, where the gas is evolved, immediately carbonizes and inflames. Alcohol, ether, benzol, spirit of turpentine, and petroleum take fire on contact.
The gas evolved at the negative pole is hydrogen, burning with a pale flame, and producing none of these reactions.
When the experiment has lasted several hours, and there is not enough hydrofluoric acid left at the bottom of the tube to separate the two gases, they recombine in the apparatus in the cold, with violent detonation.
We have satisfied ourselves, by direct experiment, that a mixture of ozone and hydrofluoric acid produces none of the reactions described above.
It is the same with gaseous hydrofluoric acid. Finally we may add that the hydrofluoric acid employed, as well as the hydrofluorate of fluoride, were absolutely free from chlorine.
The gas obtained in our experiments is therefore either fluorine or a perfluoride of hydrogen.
New experiments are necessary to settle this last point. We hope soon to lay the results before the Academy.—Comptes Mendus, vol. ciii., p. 202, July 19, 1886; Chem. News.
Comptes Rendus, vol. cii., p. 1543, and Chemical News, vol. liv., p. 36.
COHESION AND COHESION FIGURES.[1]
By WILLIAM ACKROYD, F.I.C.
1. A Law of Solubility.
It is customary to regard cohesion as the force which binds together molecules of the same substance, and in virtue of which the particles of solids and liquids are kept together, and also to speak of the attraction exerted between particles of two different bodies as adhesion. The distinction between cohesion and adhesion is a conventional one. The similarity, if not identity, of the two forces is demonstrated by the fact that while cohesion is exerted between particles of the same body, adhesion is exerted with most force between particles of allied bodies. Generally speaking, organic bodies require organic solvents; inorganic bodies, inorganic solvents. For example, common salt is highly soluble in water, but not in ether, and many fats are soluble in ether, but not in water. So many cases like these will suggest themselves to the chemist that I am justified in making the following generalization: A body will dissolve in a solvent to which it is allied more readily than in one to which it in highly dissimilar. Exceptions to the law undoubtedly exist, but none so striking as the following in support of it, viz., that the metal mercury is the only known true solvent for many metals at the normal temperature.
2. Its Connection with Mendeleeff's Periodic Law.
From this standpoint the whole subject of solution is deserving of fresh attention, as it appears highly probable that, just as Prof. Carnelley has shown by the use of my meta-chromatic scale, the colors of chemical compounds come under definite laws, which he has discovered and formulated in connection with Mendeleeff and Newlaud's periodic law,[2] so, likewise, may the solubility of an allied group of compounds, in regard to any given solvent under constant conditions of temperature, conform to similar laws; that, e.g., the chlorides of H, Na, Cu, and Ag, in Mendeleeff's Group I., may vary in their solubility in water from an extreme of high solubility in the case of hydrogen chloride to the opposite extreme of comparative insolubility in the case of silver chloride. In this natural series of compounds, hydrogen chloride is the body nearest akin to water, and silver chloride the most remote in kinship.
3. A Solidified Vortex Ring.
It is in virtue of cohesion that a freely suspended drop of liquid assumes the spherical form. If such a sphere be dropped on to the surface of a liquid of higher specific gravity at rest, one obtains what is called the cohesion figure of the substance of the drop. A drop of oil, e.g., spreads out on the surface of water until it is a circular thin film of concentric rings of different degrees of thickness, each displaying the characteristic colors of thin plates. The tenuity of the film increases; its cohesion is overcome; lakelets are formed, and they merge into each other. The disintegrated portions of the film now thicken, the colors vanish, and only islets of oil remain. Some liquid drops of the same or higher sp. gr. than water do not spread out in this fashion, but descend below the surface of the liquid, and, in descending, assume a ring shape, which gradually spreads out and breaks up into lesser rings. Such figures have been termed submergence cohesion figures; they are vortex rings. I have solidified such vortex rings in their first stage of formation. If drops of melted sulphur, at a temperature above that of the viscous state, be let fall into water, the drops will be solidified in the effort to form the ring, and the circular button, thick in the rim and thin in the center, may be regarded as a solidified vortex ring of plastic sulphur.
4. That a Submergence Cohesion Figure is a Vortex Ring.
It may be shown that the conditions of the formation of a submergence cohesion figure are those which exist in the formation of an aerial vortex. Those conditions in their greatest perfection are (1) a spherical envelope of a different nature from the medium in which the rings are produced; (2) a circular orifice opening into the medium; and (3) a percussive impact on the part of the sphere opposite the orifice. In the production of vortex rings of phosphorus pentoxide in the making of phosphoreted hydrogen, the spherical envelope is water, the orifice the portion of the bubble which opens into the air immediately it rises to the surface, and the impact is furnished by gravity. So, also, in the case of a submergence cohesion figure, the spherical envelope is the air surrounding the drop, the orifice the portion of it which first comes in contact with the liquid at rest; and here again the impact is due to gravity more directly than in the former case. These conditions are somewhat imperfectly copied in the ordinary vortex box, which is usually cubical in form, with a circular orifice in one side, and a covering of canvas on the opposite one, which is hit with the fist.
Notes from a lecture given to the Halifax Scientific Society, July 19, 1886.
Philosophical Magazine, August, 1884.