CHAPTER XXXIII.—HAMMOCK-MAKING AND NETTING.

I.—HAMMOCKS AND HAMMOCK-MAKING.

A hammock, as most of our readers are doubtless aware, is a species of swinging bed in use at sea, and especially in the Royal Navy. Its chief utility lies in the readiness and ease with which it can be taken down, made up into a comparatively small bundle, and stowed away during the day, so as to leave the deck clear. A hammock is not at all difficult of construction, and any boy who is at all handy with his fingers should be able to make one for himself.

The hammock is made of canvas, which is suspended at each end by a number of small cords, termed clews, which are made fast to hooks in the beams.

A mattress, with the usual quantity of blankets, a pillow, etc., rests upon the canvas, which, owing to the manner in which it is hung—i.e., up to the beams—assumes an oval shape, and is really one of the most comfortable things in the world to sleep in. Its only drawback is the number of opportunities it gives to mischievous messmates to play off practical jokes upon a youngster who is making his first trip at sea.

Of course this is discountenanced in the Navy, but it is impossible altogether to prevent it; and no doubt many a victim to a slippery hitch could bear witness to the truth of this.

A slippery hitch, we may as well inform our readers, is a species of slipknot tied in the lanyard which connects the clews and the hook in the beam. It appears all right to a casual observer, but when the victim gets into his hammock his weight begins to tell, and the knot slips away and precipitates the sleeper on to the deck.

Then, again, there was the custom, which we hope and believe has gone out of fashion now, of ‘cutting down,’ which was effected by applying a sharp knife to the lanyard, and letting the sleeper down, generally head foremost.

Fig. 1.

Now with respect to making a hammock, the first thing necessary is a piece of strong canvas, about 5 ft 8 in. in length and 3 ft. wide. In the Navy hammocks are made in two pieces ([Fig. 1]), which are stitched together down the centre (B). The sides and ends must be hemmed, and then the eyelet-holes for the clews to be fastened to must be made (A A). The eyelet-holes are twenty-four in number, at equal distances along the edge, at each end of the hammock. They are usually made in the following manner, although it is not absolutely necessary to be so particular.

A number of small rings made of white line (a kind of whipcord) are prepared, which are called grummets. These are placed in the eyelet-holes, and then sewn over all the way round with thin twine.

The next thing to make is a pair of clews. These are composed of what are termed at sea knittles, which are two or three yarns laid up together, by a jack or by hand, against the twist of the yarn. But good cod-line or anything else sufficiently stout, will answer the purpose equally well. The following is the proper way to make clews, although it is now sometimes dispensed with:—

Take twelve knittles about 5 ft. in length and double them. Then form an eye in the middle, which must be served with fine twine. This is done by winding the twine round and round as tightly as possible for a sufficient distance to form the eye; then seize or bind the knittles together for about an inch below the eye, as in [Fig. 2].

Fig. 2.

Fig. 3.

Fig. 4.

Now take a piece of twine, about half the size of the knittles, and place it between the knittles, so that twelve come up and twelve go down ([Fig. 3]); next bring both ends of the small twine, which is called filling, back again between the knittles, only altering them, making the upper ones point down and the lower ones point up; then leave out the two outside knittles and continue the circuit, leaving two knittles out each time until you come down to the last two, when knot the filling together and cut off the ends ([Fig. 4]). The ends of the knittles are then passed through the eyelet-holes in the canvas and fastened with two half-hitches. For the Navy now a great many clews are made without the platting arrangement we have described, and are left quite plain from the seizing below the eye down to the eyelet-hole. But the description we have given is of the old-fashioned style, and to our mind it looks much neater and more ornamental.

Fig. 5.

A piece of rope, called a lanyard, must now be spliced with an eye-splice into the eye of the clew that is to form the foot clew, and the hammock is completed.

In order to sling this it will be necessary to purchase a couple of stout hooks which will screw into the woodwork. These are easily obtained at any ironmonger’s, and may be fastened at the two opposite corners of a room, or in two trees in the garden at a convenient distance apart.

Then hook the head clew on, and pass the lanyard over the other hook, get the hammock level, and fasten it with a clove-hitch or two half-hitches.

And now one word of caution with regard to getting into a hammock. Be very careful the first time or two, and take notice how the hammock recedes, and then swings towards you. If you jump into it in the same manner as you would into a bed, the chances are that you will go right over it, and land on the ground the other side; but with a little care the proper method does not take long to learn.

II.—NETTING, AND HOW TO NET.

To the reader who is desirous of learning the art of netting, we must give the same advice that the famous Mrs. Glasse did with reference to cooking a hare, viz.: ‘First obtain your hare.’ That is to say, the first thing is to obtain the netting instruments and materials.

Fig. 1.
A, The needle. B, The mesh stick. C, The twine.

The instruments consist of a needle and a mesh (see [Fig. 1]). From eight to ten inches is a good length for the needle, while the mesh stick must vary according to the size of the net you are about to make. A mesh stick will make a mesh twice its own size. Thus a stick half an inch square will make a one-inch mesh.

Any youth at all handy with a knife can manufacture these articles for himself, and there only remains to obtain the material. This must depend upon what is going to be made, for once the stitch is learned there is no more difficulty in making a large seine than in making an onion net or a network hammock.

Fig. 2.

Fig. 3.

The better plan is to go to the nearest string shop, and pick out what is suitable in size and strength as well as in price. When the material is purchased—white line, seine twine, or common twine, whatever it may be—if it is not already in a ball, wind it into one. Then find a hook, or place one just a convenient distance above you as you sit, to which to fasten the end of the twine. Now fill your needle, pass the twine round the tine, or inside point, round the heel of the needle, then up round the tine again, until the needle is full. Now fasten the end of the twine to the hook—a nail, if it be firm, will answer the same purpose—and tie a loop in it ([Fig. 2]). Then lay the mesh stick underneath the twine, and pass the needle up through the loop ([Fig. 3]). Then pull it tight, so that the end of the loop rests against the mesh stick ([Fig. 4]).

Fig. 4.

Fig. 5.

Fig. 6.

Now comes the important part, the formation of the knot. Hold the mesh stick in your left hand, with the thumb on the twine, and with the needle in the right hand. Now with a quick jerk throw the bight or loop of the twine over the stick and left wrist, as shown in [Fig. 5].

Then push the point of the needle up between the first loop made, and the twine to the left of it, pull the needle through, and bring the knot into shape ([Fig. 6]), then tighten by pulling the needle in the direction of the dotted lines, and the knot is tied.

This simple knot is the foundation of all net-making, and once the reader succeeds in making that, he will very quickly be able to manufacture anything he may require in that branch of work.

Fig. 7.

Now slip out the mesh stick and take the same stitch through the loop you have just made, and so continue on, passing the needle every time through the last loop made until you have made enough. You can generally guess the number of meshes you will require by the size of the mesh stick. By the time you have made as many as you think will be requisite, your work ought to look something like [Fig. 7].

Next unfasten the end from the hook or nail, and untie the first loop made, because it is not the same size as the subsequent ones. Now pass a piece of cord through the upper row of meshes, tie the ends of the cord together, and hang it again over the hook.

Fig. 8.

Next go on with the work as before, only do not slip the loop off the stick as at first. Knot through E, [Fig. 8], then through D, then C, and so on, until you have travelled along the whole width.

Then turn the work over and travel back again in the same manner. It is better to make ten or a dozen meshes before slipping the stick out.

Fig. 9.

Presuming that the twine breaks, or you wish to join another ball, the way to do it is with a ‘becket-hitch,’ commonly called a ‘weaver’s knot.’ Form a bight with one part, pass the other part up through the loop, then over, under and back through its own loop ([Fig. 9]).

With regard to making a network hammock, proceed as we have described, and to make a full-sized hammock you would require between fifty and sixty two-inch meshes each way.

Then make the clews, as described in the [article] on canvas hammocks, and fasten them in the usual manner to each end of the hammock, tying the ends as regularly as you can.

Netting is a very pleasant as well as useful occupation, and is more suitable for boys than girls, owing to the strain of pulling the knots tight. The pleasure of being able to make nets for fishing, nets for the garden, to keep the birds off the trees, nets to hang vegetables or fruit in, and lastly, but not least, a net hammock, ought to amply repay any trouble or inconvenience caused by learning.

CHAPTER XXXIV.—A PERPETUAL CALENDAR.
By Herr H. F. L. Meyer.

EXPLANATIONS.

Various perpetual calendars have been published, but some of them are very elaborate, and others incorrect; therefore, by the editor’s invitation, I now present one in a most handy form. [Table 1] shows the centuries, with the key numbers; [Table 2], the last two figures of the year, and the seven key numbers below; [Table 3], the months; and [Table 4], the days. The key numbers are printed thick, the leap years in italics. January and February have two keys each, 3 and 6 for common years, 2 and 5 for leap years. The eleven days from September 3rd to 13th, 1752, were omitted. Every year which divides by 4 without a remainder is a leap year, except the centenaries, which are printed upright.

Table 1.Table 2.Table 3.Table 4.
First 2 00010203 0405Jan.32[3]1234567
100 1 0607 08091011Feb.65[3]891011121314
200 0 12131415 16Mar.6 15161718192021
300 6 171819 202122Apr.2 22232425262728
400 5 23 24252627 May4 293031
500 4 28293031 3233June0 0SMTWThFS
600 3 3435 36373839July2 1MTWThFSS
700 2 40414243 44Aug.5 2TWThFSSM
800 1 454647 484950Sept.1 3WThFSSMT
900 0 51 52535455 Oct.3 4ThFSSMTW
1000 6 56575859 6061Nov.6 5FSSMTWTh
1100 5 6263 64656667Dec.1 6SSMTWThF
1200 4 68697071 72
1300 3 737475 767778
1400 2 79 80818283
1500 1 84858687 8889
1600 0 9091 92939495
1700- 6[1] 96979899
2[2]0123456
1800 0
1900 5
2000 4
2100 2
2200 0
2300 5
2400 4

[1]6 till Sept. 2, 1752.

[2]2 from Sept. 14, 1752.

[3]for leap years.

EXAMPLES.

Example No. 1.—What day of the week was the 21st of June, 1581?

1500—key1in Table 1.
81—key3in Table 2.
June—key0in Table 3.
Total4,the three keys added.

This 4 is the key for [Table 4], where, on the right-hand side of this key, under the 21 st day, we find Wednesday.

If the three keys together make more than 6, seven is subtracted; and if more than 13, fourteen is deducted, and the remainder is the key to [Table 4].

Thus we find June 6th, 1839, through 0 + 6 + 0 = 6, = Thursday.

August 9th, 1732, through 6 + 5 + 5 = 16, - 14 = 2 = Wednesday.

Columbus sailed from Palos on Friday, August 3rd, 1492, and discovered America on the 12th of October, 1492, which was also a Friday.

Example No. 2.—In what years will Christmas Day fall on a Sunday? [Table 4] shows, below the 25th, the Sunday on the side of key 4; subtract the key of December, which is 1, there remains, for the present century, the key 3 of [Table 2], showing the years 1887, 1892, 1898 and as this 4 for the next century will come from 5 + x + 1 minus 7, it follows that x means the key 5 in [Table 2], which contains the years 1904, 1910, 1921, and the other years in that column.

We found the 6th of June, 1839, to be a Thursday, and see from the last column of [Table 2] that it was again on a Thursday in 1844, 1850, 1861, etc.

Any one born on the 29th February, 1864, will have his birthday again on the same day of the week, a Monday, in 1892, that is, after an interval of 28 years, as is seen in the middle column of [Table 2]; and after that he will have it again on a Monday in 1904, 1932, etc.

HISTORICAL NOTES.

Romulus, the founder of Rome, established a year consisting of ten months, named Martius, Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, and December; but in the succeeding reign, that of Numa, two months were added, called Januarius and Februarius.

Julius Cæsar, aided by Sosigenes, an Alexandrian astronomer, instituted the Julian Calendar, which has come down to our own epoch. It was then decided to give an additional day to every fourth year. The date of the reform was 45 B.C., which was the Roman year 708, dating from the foundation of Rome. The Julian year began on the 1st of January, 708 A.U.C., and ended on the 31st of December, 709 A.U.C. In the first 48 years of the reform there prevailed some confusion about the bissextile or leap years, because during the first 36 years every third year was reckoned a leap year (12 intercalations had taken place instead of 9); but, in order to rectify the error, the next 12 years (i.e. 9 B.C. to 3 A.D. inclusive), elapsed without an intercalary day, by decree of Cæsar Augustus, who also changed the names of Quintilis and Sextilis into Julius and Augustus, in honour of his uncle and himself. Thus the Roman years, 757, 761, 765, 769, etc., which were the years A.D. 4, 8, 12, 16, etc., were counted as leap years, and about all succeeding dates there is no doubt.

‘It was probably,’ writes Mr. Bond, of the Record Office, in his valuable work, ‘the original intention of Cæsar to commence the new year with the shortest day, the winter solstice at Rome, in the year 46 B.C. (common era), occurring on the 24th December of the Julian calendar. His motive for delaying the commencement for seven days longer, instead of taking the following day, was no doubt the desire to gratify the superstition of the Romans, by causing the commencement of the first year of the reformed calendar to fall on the day of the new moon, for it is found that the mean new moon occurred at Rome on the 1st of January, 45 B.C. (common era), at 6 h. 16 m. p.m.’

The Christian era was introduced in Italy, in the 6th century, by Dionysius the Little, a Roman abbot, and began to be used in Gaul in the 8th, though it was not generally followed in that country till a century later. From extant charters it is known to have been in use in England before the close of the 8th century. ‘At first, in A.D. 533,’ says Mr. Bond, ‘the era began with the 25th of March, but was subsequently reckoned from Christmas Day, the 25th of December, and in the 13th century, in some countries, was reckoned from the 1st of January according to the Julian era.’

The exact length of the mean solar or civil year is

365 d. 5 h. 48 m. 46 s.,

therefore the Julian year, being 365 days and 6 hours, departs from the course of the seasons at the rate of 11 m. 14 s., and consequently Aloysius Lilius, from Calabria, a physician and mathematician of Verona, projected a plan for amending the calendar, which induced Pope Gregory XIII. to introduce the plan on the 5th October, 1582, according to the former style, which day was decreed to be called the 15th October. These 10 days rectified the error of the past, in accordance with the day of the equinox, the 21st March. The error of the future, which was that an additional day every fourth year was too much, but that 129 years must elapse before the redundance would cause the equinox to be one day behind its time, was rectified thus: Adding 129 years to the year 1582 there results the year 1711, and it was decreed that the year 1700, which would, by the Julian Calendar, be a leap year, should be a common year, but, as stated below, it was still kept as a leap year in England, and appears as such in [Table 1]. In like manner 1800 was made a common year, and as in 1969 the 21st March would be a day behind the vernal equinox, it will be set right by making 1900 a common year. Another period of 129 years would extend to 2098, which will be remedied by making 2100 a common instead of a leap year.

Thus the equinox will be kept right by making three successive secular years common years; and the secular leap years will be those of which the first two figures are divisible by 4 without a remainder, as 2000, 2400, 2800, etc.

The keys or index figures in accordance with the Gregorian reform are these:—

CENTURIES. KEYS.
1400 2
1500- 1 till October 4, 1582.
5 from October 15, 1582.
1600 4
17002
18000

The Papal decree of October, 1582, was adopted in France in December, 1582, in Poland in 1586, in the Catholic States of Germany in 1583, in the Protestant German States, through Weigel’s Calendar, in 1700, in Denmark and Switzerland soon after the adoption in Germany, in England in September, 1752, whereas Russia still adheres to the Julian Calendar. Thus the Russian legal equinoxes are now twelve days in advance of the real equinoxes.

In England the years used to begin upon the 25th March, but it was declared that 1752 should end on the 31st December, and 1753 begin on the day formerly called the 1st January, 1752. At that time the people in England used to write the new style under the old, thus:—

30th June, 11th July, 1753.

25th February, 1753. 8th March, 1754.

The death of Charles I. took place on Tuesday, January 30, 1648, as written at that time, but it is now written January 30, 1649, and often expressed by historians thus:—January 30, 1648-9.

In Scotland, the day after 31st December, 1599, was called 1st January, 1600.

The 4th August, 1581, was a Friday in all parts of Europe, but from 1582 to 1752 there was a variance in various parts, as there still is at present, between the east and the west of Europe. The variance was in the days of the month; the days of the week never changed. The 2nd September, 1752, was a Wednesday in England and in Russia, but a Saturday in the other States of Europe. Thus we find the 20th December, 1647, for England and Russia, through 0 + 2 + 1 = 3 = Monday, but for Italy, France, Spain, etc., through 4 + 2 + 1 = 7 - 7 = 0 = Friday. The 14th September, 1752, was a Monday in Russia, but a Thursday in England and the other European States. The 21st June, 1887, was a Tuesday in England, but in Russia it was twelve days later, that is, a Sunday, namely, the Sunday on which we had the 3rd of July. The Russians had the 9th June, 1887, on a Tuesday, that is the day on which we had the 21st June; and in writing to us they express that day thus:—June 9 21, 1887. They have the key 6 for 1700, and 5 for 1800.

The Turks use the Mohammedan Calendar, from the Hegira, July 16, A.D. 622, and it is lunar like the Jewish.

The following historical dates agree with our calendar:—

The battle of Hastings was fought on Saturday, Oct. 14th, 1066.

The Magna Charta was signed on Sunday, May 24, 1215.

Edward II. was crowned on Sunday, 25th February, 1308 (1307 in the old style).

The battle of Crecy took place on Saturday, August 26th, 1346.

The battle of Towton, Yorkshire, occurred on Palm Sunday, March 29, 1461.

THE KEY NUMBERS.

The keys for the centuries and months can be arranged at pleasure, therefore the key 0 is chosen for the present century to calculate readily the dates of our time. To make the reckoning easy in the next century it will be well to have the key 0 for 1900, then the keys for the months must all be reduced by 2, and the tables will be:—

Jan.1and 0May2Sept.6
18002Feb.4and 3June5Oct.1
19000Mar.4 July0Nov.4
20006Apr.0Aug.3Dec.6

CHAPTER XXXV.—HOW TO MAKE A SUNDIAL.
By F. Chasemore.

I.—THE HORIZONTAL DIAL.

A very useful and instructive pastime for boys will be found in the construction of a sundial, full directions for making which I give in this chapter.

Fig. 1.

[Fig. 1 enlarged] (112 kB)

The first thing to be done is to make what is called the dialing scale ([Fig. 1]). It is constructed as follows: With a pair of compasses describe the circle A B C D with any radius, say four inches. Draw the two diameters A C and B D, cutting each other at right angles in the point 0. Join D C for the scale of chords and B C for the scale of latitudes. Through the point B draw the straight line 12—6 parallel and equal to the line A C, and let the point B bisect it. Join the points 0—12 and 0—6, cutting the circle in the points E and F. Now divide the arcs E B and B F each into three equal parts, and from the point 0 draw straight lines through these points of division to the line 12—6, marking the points of intersection 12, 1, 2, 3, 4, 5, 6. This line is called the line of hours.

To make the scale of chords, divide the arc D C into nine equal parts, and then with the compasses, with one leg placed on the point C, protract each division on the line C D. Mark the points on this line from C 10, 20, 30, etc.; the point D will mark 90 degrees.

To make the scale of latitudes, draw lines from the points of division in the arc D C parallel to the line D 0, and cutting the line 0 C in points, counting from 0, 10, 20, 30, 40, etc. Now draw straight lines from D through these points, cutting the arc B C in the points 10, 20, 30, etc., and with your compasses, with one leg on B, protract these distances on to the line B C, which will be the scale of latitudes. Now our dialing scale is finished.

To make the dial, which will be a horizontal one, you must get a piece of zinc plate about one foot square. On this mark all round it, and one inch from the edges, lines making a smaller square of ten inches a side. Plate 1⁄8 inch thick.

Bisect one line of this square, and draw a line from this point to a point bisecting the opposite side. Now draw two other lines, one on each side of, and one-sixteenth of an inch from, this line, and parallel to it. These lines will then be one-eighth of an inch apart. They are made this distance apart as the style, or gnomon, will be that thickness, and has to stand between them. Now divide the other sides into five equal parts, and join the two second points of division, counting from the bottom. This line, which is called the six-o’clock line, will cut the two parallel lines in the points A C ([Fig. 2]). Mark the other or top ends of these lines B and D.

Fig. 2.

Now with your compasses take from the scale of latitudes the latitude of the place where you wish to erect your dial. Suppose you are in London, put one leg of the compasses on the point B, and the other leg on the point in the scale of latitudes marking 511⁄2 degrees, which is the latitude of London. Now mark this distance off on the six-o’clock line from C to E and from A to F ([Fig. 2]). Now take the length of the line of hours from 12—6 in the compasses, and, putting one leg on the point E, intersect the line C D in the point G. Do the same on the other side, putting one leg on point F, and intersecting the line A B in the point H. Draw the lines G E and H E ([Fig. 2]).

These lines are the same length as in the line of hours; mark them as that line is marked, using your compasses to get the distances, marking the line from G to E and from H to E; now from the point C draw lines through the divisions on G E to the lines of the inner square; do the same from point A through the line H F. The fourth and fifth lines on the right side must be continued back through the point C to opposite side of square, and the seventh and eighth on the left be continued back through A to right side. Now mark the hours. The double line is the twelve-o’clock line, and must be marked twelve. The line to the right is the one-o’clock line, the next two, and so on to eight on the right side. On the left the line next the twelve-o’clock line is eleven, the next ten, and so on back to four. All the lines can be marked on the zinc with a pointed bradawl.

The dial plate is now finished.

Fig. 3.

The next step is to make the gnomon. For this get a piece of the same zinc plate about six inches by eight. Along one of the shorter sides, about a quarter of an inch from the edge, draw a line A B, making it equal in length to C—60 on the scale of chords. With one leg of the compasses on the point A, and the other opened out to B, draw the arc B C as in [Fig. 3]. Now from the same scale of chords take the length of the latitude of the place, and mark it along the arc B C from B, join A C, from C draw a line at right angles to A B, cutting it in the point D ([Fig. 3]). The triangle A D C will be the gnomon, with the line A D for its base. Cut this triangle out carefully, making the edges quite square. Now you must get a tinman to solder this in its place on the dial-plate, the point A of the gnomon to be at the points A C on the plate, and the line A D along the two lines A H and C G. You must be very careful that the gnomon stands at right angles to the dial-plate.

The dial must be fixed in a sunny spot, if possible in the middle of a large lawn. The best way to do this is to fasten the dial-plate on a square board, which is fastened to a post driven into the ground. The post can be ornamented with rustic work. The dial must be quite level, and the gnomon pointing due north.

The line A C of the gnomon being made at the angle from the base equal to the latitude of the place will be parallel to the axis of the earth, and will show the hours correctly both on long and short days, as the sun’s course is at right angles to it. The dial can be made to show quarters or five minutes if you so divide the line of hours on the dial scale. The dial, if placed in an open, sunny spot, will show the hours from sunrise to sunset.

II.—THE EQUATORIAL DIAL.

The horizontal sundial would be suitable for all places north and south of the equator. But in southern latitudes the style must point due south instead of north, and the numbering must be done from right to left instead of from left to right. The method, however, already described would not do for any place situated exactly on the equator. The reason for this is—the style, or gnomon, being parallel to the axis of the earth, it would be horizontal at the equator, and perpendicular at the poles, and the shadow would be parallel to the style at the equator and perpendicular to it at the poles. The style must be regulated in height by the size of the dial-plate, and the length of the line of hours, in the scale, must be regulated by the height of the upper edge of the style from the dial-plate.

Fig. 1

I will now explain the construction of the equatorial dial. The dial-plate is to be cut about eighteen inches long by twelve inches wide. The inner lines are to be drawn all round, about one inch from the edges, as in the dial already described. Divide the dial-plate into two equal parts by a line drawn from points bisecting the long sides, as in [Fig. 1] in the accompanying illustrations. This line is the twelve-o’clock line. The two lines A B and C D are to be drawn parallel to this line, one on each side of and a sixteenth of an inch from it. Before the hour lines can be drawn the style must be made. This must be rectangular in shape, with the long sides equal in length to the twelve-o’clock lines between the inner lines of the plate, and must not, for this size of dial-plate, be more than two inches wide or high. The dialing scale must now be made. It consists only of the line of hours. Draw the two lines O A and O B at right angles to each other, and make each equal in length to the height of the gnomon, or style—viz., two inches. Draw B C parallel to O A, and make it about ten or twelve inches long. Describe the arc A B, with O for the centre, and O A and O B for radii, as in [Fig. 2]. Divide this arc into six equal parts, and draw lines from the point O through the points of division to cut the line B C in the points 1, 2, 3, 4, 5. The six-o’clock point will not be required. This is the line of hours. With your compasses mark on the side lines of the dial-plate, from the points A B and C D, the divisions of the line of hours. Join the corresponding points on each side of the twelve-o’clock line by lines drawn parallel to it. These lines will represent the hours, and are numbered 1 to 5 to the right and 11 to 7 to the left. [Fig. 3] shows this dial.

Fig. 2

Fig. 3

This dial does not show the time before seven o’clock in the morning or after five o’clock in the evening. The reason of this is, the days and nights at the equator being equal—viz., twelve hours each—the sun rises and sets at six o’clock. At six o’clock, the sun being exactly on the horizon, any object placed in the middle of a perfectly horizontal plane would cast an indefinite or unlimited shadow, as the shadow of the upper part would be parallel to the plane, and of course could not meet it. The dial can be made to show any time after six in the morning or before six in the evening by lengthening the dial-plate. [Fig. 4] will show how inconvenient it would be to have a plate to show the time before seven or after five o’clock. In [Fig. 4] the hour from five to six is divided into quarters, and shows that for 5.30 the plate must be about double, and for 5.45 about four times, the length required to show the time between seven and five o’clock. So that a plate about six feet long would be required for a dial having a style two inches high.

Fig. 4

The style is to be soldered to the dial-plate between the two lines A B and C D, and must be equal in thickness to the distance between them. The dial must be set up in a horizontal position with the gnomon directed due north and south.

Both these dials are horizontal. I will now explain the construction of vertical dials, or dials that are fixed in an upright position against a wall or house. The dialing scale, as already described, will be required for the construction of a vertical dial to be fixed on a wall facing the south.

Cut the zinc plate twelve inches square, and mark it with the inner square, the twelve-o’clock lines, and the six-o’clock line, as in the horizontal dial. From the line of latitudes, in the scale, take the length equal to the difference between 90 deg. and the latitude of the place (that is, not as in the horizontal dial, the latitude, but the complement of it).

Fig. 5

Taking London as the place, take from the scale 381⁄2 deg., which is the difference between 90 and 511⁄2 deg. This distance must be marked off on the six-o’clock line from the points A and C. The rest of the construction is the same as for the horizontal dial, with the exception that the hours are limited to fourteen, viz. from five to seven o’clock, and are numbered backwards, or from left to right as in [Fig. 5]. The style is made as for the horizontal dial, but the angle C A B is to equal 381⁄2 deg. in the case of London, or the complement of the latitude. The base A D is to equal the length of the twelve-o’clock lines, measuring from the six-o’clock line to the inside line at the lower edge, or the lines A B and C D. In fixing this dial care must be taken to let it face due south.

Fig. 6

Fig. 7

Fig. 8

Fig. 9

The east and west vertical dials are made something like the equatorial horizontal dial, with a rectangular style. The same scale is required for making the line of hours, the lines of which are regulated in length by the height of the style. Make the plate about eighteen inches long and twelve inches wide, and draw the double lines which in these dials represent the six-o’clock line, as in Figs. 7 and 8. These double lines are drawn, making an angle with the lower edge of dial-plate equal to the latitude of the place. The style is cut rectangular, with the long sides equal to the double six o’clock lines, and the short sides two inches long. Draw the scale making O A and O B two inches long, and mark the hour line. Before the points on the hour line can be marked in on the dial-plate, a plan ([Fig. 9]) must be made. Draw on a large piece of paper a plan of either dial-plate, and mark in the double lines. Through these draw the line A B perpendicular to them as in [Fig. 9]. On this line, on each side of the double lines, mark the points on the hour line, and through these points draw lines parallel to the double lines, and letting them cut the sides of the plan of the dial-plate. The points where the lines cut it can be transferred to the dial-plate with a pair of compasses, and the hour lines drawn in parallel to the six-o’clock line. The style must be fixed in its place, and will be parallel to the axis of the earth when the dial is fixed up with the long sides quite horizontal. The east dial is marked as in [Fig. 7], and the west as in [Fig. 8], if for the northern hemisphere. For the southern, the west dial would take the place of the east, and the east, the place of the west with the numbering reversed.

There are several other kinds of sundials, which may be used for any degree of latitude, a few of which I will describe.

The first of these is the globular ([Fig. 10]). This is a white globe (any size), supported on an axis which is fixed in a position parallel to the axis of the earth (or making an angle with the horizon equal to the latitude of the place, and pointing due north or south), in which position the globe is acted on by the sun exactly as the earth is. The globe is divided into twenty-four equal parts by lines running from pole to pole, and has an equator drawn around it, on which the hours are marked from 1 to 12 twice over. The axis is fixed in a stand so that one of the six-o’clock lines is in the zenith. The time is indicated by the edge of the shaded part (caused by the sun illuminating one-half of the globe, leaving the other in shade) passing over the hour lines. An ordinary globe answers very well for this dial, if it is rectified for the latitude, and placed so that the brass meridian is directed north and south.

Fig. 10

Fig. 11

[Fig. 11] is another pattern; it is basin-shaped, and is made of a hollow hemisphere of metal, whitened inside, and has the inside divided into twelve equal parts by lines running from pole to pole, which are numbered on the equator from 6 to 6. A wire is stretched from pole to serve as the style, which casts a shadow on the line corresponding to the hour. The position of this dial is the same, as regards the axis of the earth, as [Fig. 10].

Fig. 12

[Fig. 12] represents what I call the trough-shaped dial. It is made of metal-plate bent into the shape of a half-tube; the ends are closed with semicircular metal plates. The interior is divided into twelve equal parts by lines running parallel to the edges, and are numbered from 6 to 6. A wire is stretched from the centres of the semicircular end plates to serve for the style.

This dial must be fixed, with regard to the position and direction of the style, as the other dials are. This is the one constant condition of all dials, that the edge of the style that is to cast the shadow must be parallel to the axis of the earth.

Fig. 13

[Fig. 13] is a very simple dial, and is the last I shall describe. It consists of a circular dial-plate divided into twenty-four equal parts, numbered from 1 to 12 twice over. The style is a perpendicular wire fixed in the centre of the plate. The plate is hinged to a stand, so that one of the twelve-o’clock lines runs directly from the top to the bottom.

From the construction of the [dials 10], [11], [12], [13], they can be used in any latitude, as well as on the equator, but of course the numbering would have to be reversed for the southern hemisphere. They all have an arrangement by which the style can be fixed at the required angle to suit the latitude of the place.

TABLE OF MINUTES.
To be Added to or Subtracted from the Sundial for each Day in the Year.

The sun does not always point out the true time, as on some days it is behind time and sometimes before it. The table below gives the minutes to be added to or subtracted from the time pointed out by the sun for each day in the year:—

January.
Day.Min.
1+4
4+5
6+6
8+7
11+8
13+9
16+10
19+11
23+12
27+13
31+14
February.
3+14
19+14
26+13
March.
3+12
4+11
12+10
15+9
19+8
22+7
25+6
28+5
April.
1+4
4+3
8+2
12+1
19-1
25-2
30-3
May.
1-3
17-4
28-3
June.
4-2
10-1
19+1
24+2
29+3
July.
4+4
10+5
19+6
August.
1+6
11+5
16+4
21+3
25+2
29+1
September.
4-1
7-2
10-3
13-4
16-5
18-6
21-7
24-8
27-9
30-10
October.
3-11
7-12
10-13
14-14
19-15
27-16
November.
10-16
17-15
21-14
25-13
28-12
December.
1-11
2-10
6-9
8-8
10-7
12-6
14-5
16-4
18-3
21-2
23-1
27+1
29+2
31+3

CHAPTER XXXVI.—THE CAMERA OBSCURA: HOW TO MAKE AND USE IT.
By Gordon Stables, C.M., M.D., R.N.

Did you never, reader, have a peep in beneath the black cloth where the artist hides his head while he is focusing a sitter for his photograph? I’m sure that many of you have. And what did you see? Why, a pretty little picture in colours of your friend sitting in the chair, laughing like a tramp at a twopenny roll, only upside down. And you have said to yourselves, What a pity it won’t come out in bright colours like that, and why in all the world should it be upside down?

Now I will answer this question before going any further, because it has a bearing on the subject before us—the making of a handy and cheap camera obscura, which cannot fail to be a source of amusement and pleasure, especially when the sun shines.

The reason why the object on the photographer’s ground-glass plate is seen upside down is easily explained. Light, as I need hardly remind older boys, proceeds in straight lines from any illuminated object. It is thus thrown upon the photographer’s plate. A glance at the accompanying diagram ([Fig. 1]) will suffice to show what I mean.

Fig. 1.

Let A B be the object—say, an arrow—under consideration, and C D a side view of the ground-glass plate on which the picture is seen. Passing, therefore, in straight lines, the light and colour from the point A will fall at a, will they not? and those from B at b, and so on from every portion of the arrow, so that the representation therefore on the object-glass will be upside down, or reversed. Q.E.D.

Now about the camera. No one can be said to have invented it, for it is constituted upon the firm and immutable laws of Nature. Roger Bacon is credited with having known this principle. Very likely he did, but he put it to no practical use, though over four hundred years after his time Giovanni Baptiste Porta did. But who knows that the ancients hundreds of years before the Flood were unacquainted with it? Here, for example, is a story a little bird told me one beautiful summer’s day while reclining on the greensward in my woodland study: I had been reading under the shade of my great oak-tree. The sun was very bright, and patches of its light penetrated even through the dark-green branches and fell on my face. Probably it was that which set me a-thinking about the laws of optics and the camera obscura and camera lucida. Suddenly close up above me a bird alighted—it was early in the season—and began pouring out the most charming notes.

‘Many people,’ I said to myself, ‘would take that bird to be the nightingale, but I know it is only a black-cap.’

The words were hardly out of my mouth when a saucy little head with a bright bead of an eye peeped round the corner of a twig at me.

‘Only a black-cap!’ said the owner of the head and the eye. ‘I’d have you know, sir, that we black-caps, as you call us, are of a far older family than the nightingales, and that they first learned their wild notes from us, and not we from them!’

‘You know a deal, I dare say,’ I replied. ‘Can you explain this, then? There is a streak of light creeping in from a point among the boughs up there, and falling on my foolscap, and whenever a pigeon, or hawk, or rook flies past away overhead, his image appears on the paper and crosses it, only in a contrary direction.’

‘Foolscap, indeed!’ replied the bird, ‘it is yourself that should be wearing one. The image on your paper is caused by the reflection of the luminous rays from the flying bird. Now,’ continued the black-cap, ‘I’ll tell you about the camera.

‘You know the ancient Egyptians understood everything!’

‘So they supposed,’ I grunted, ‘but——’

‘Don’t interrupt, please. The dungeons of that mysterious land were once upon a time small and dark and dismal in the extreme, and for a very little fault indeed people were thrown therein, perhaps never to leave them alive.’

‘Well, it came to pass that a certain poor man had offended the king, and all his worldly goods were confiscated and he himself was thrown into a cell in a rock. It was not a large one, and its walls were smoothly cemented with a mixture of lime and sand, and some other ingredients known only to the ancient Egyptians. The cell was situated in the side of a hill, with a door at one side which was opened only once a week, to thrust in a pitcher of water and a bundle of cassava root, on which the poor man lived, and to have the cell cleaned out. The only aperture for light and air was a little round hole at the front of the room, too small for even a bird to get through, though bees and moths often entered and kept the prisoner company. But, lo! every day and all day, especially when the sun shone, the rays of light through that aperture brought with them a picture which they painted on the opposite wall. This picture was upside down, but that was but a small drawback, and everything that happened out of doors or in the city beneath was painted on the wall in a marvellous manner. But when the cell door was opened the picture faded away, so the gaoler never saw it.

‘One day the prisoner addressed the gaoler as follows: “Speak unto the king for me, O my son, and tell him, if all my trespasses are forgiven me, and I am taken up out of this loathsome den, I will build for him in his palace a dark room in which he can sit and see all that is going on in the city beneath spread out before him like a great moving picture.”

‘And the gaoler went and spoke to the king in the prisoner’s behalf, and the poor man was brought before the king and set to work in a room of the palace tower. With the aid of workmen he turned the room into a camera obscura, by means of well-placed steel mirrors casting the picture down upon a white concave table.

‘When the king saw it he was greatly astounded and delighted, and ever after that there was no guest about the palace so greatly honoured as the poor man he had but lately thrown into a dungeon.’

I began to rub my eyes after this, and I am hardly sure yet whether the black-cap had really been speaking, or whether I had dropped asleep and been dreaming.

However, this prisoner did nothing more than you could do. I slept, when a boy, in a little turret chamber, which I easily converted into a camera, a description of which I had read in an old book on ‘The Arts and Sciences.’ I had a white screen placed at the proper focus, and a tiny round hole in the shutter, that was all. It was a very primitive arrangement, but pleased me then.

And I believe that most of my readers who are over twelve can make a handy portable camera from the hints I shall now give.

Before you read any further, then, get an empty matchbox, and put it on the table, bottom upwards. Now draw out the drawer of it about half-way. That matchbox is your rough model for the portable camera. Simple, is it not?

Fig. 2.

The sketch I here append, however ([Fig. 2]), is not that of a matchbox, but of your portable camera itself, minus its dark shade. The size of this portable camera will depend upon, and be in the ratio of, your own ambition; the perfection of its make will depend upon your own ingenuity.

1. Well, then, you are to make or get made a small box of either very thin wood or very strong pasteboard, covered with thin cloth and painted some dark colour. Size, say, six inches high, six inches wide, and one foot long. This box is open only in front, and therein fits or slips the focusing drawer with its lens.

2. This drawer is also of the same material, and is open at the end that fits into the box, that is the end opposite the lens, and should work easily in or out, and admit no light except through the lens, the magnifying power of which need not be very great.

3. The whole interior of box and drawer is to be stained of a dull black colour.

4. Into the top of the box is let a piece of ground glass, occupying the whole breadth nearly of the top, and two-thirds of its length.

5. Into the box is fitted or let a mirror, which faces the drawer and lies at an angle of forty-five degrees.

Now turn your eyes to [Fig. 2], and I will try to explain it. The dimensions of the box are marked in plain figures, as the drapers say. The length of the drawer is about five inches or less. This drawer is represented in the figure as pulled about half-way out. When shut up it will reach the letters C A. The lens is about an inch in diameter, and may be bought cheap at any optician’s, or even fitted for you there.

The piece of ground glass on the top occupies the position marked out by the letters F, E, B, G.

The mirror inside occupies the position indicated by the dotted line A B.

But your camera is not complete yet. You have your dark shade to slip on and fasten. This shade (vide [Fig. 3]) is a lid, open at both ends, that goes right over two-thirds of the whole box when closed, covering that portion of it seen in [Fig. 2] between the squares F, E, G, B and E, H, B, I. This lid is fixed by means of a close-gummed cloth hinge to the box at the dotted line F, E. It is free every way else, so that, when lifted up to an angle of forty-five degrees, it keeps the light away from the ground-glass top, and permits you to see the picture thereon. This shade is, of course, also stained of a dark colour internally.

Fig. 3.

Now your portable camera is complete. To use it, all you have to do is to hold it in your hand, with the lens turned towards the picture you want represented, and the shade raised, then to pull the focusing-drawer in and out till you have a clear, well-defined picture on your ground-glass top. When the sun is shining brightly the effect is charming; but you yourself and camera ought to be well in the shade.

Now, the instrument I describe is very simple, but its principles may be extended. You might have it on a stand with racks and pulleys for adjustment; and you may have a dark cloth over the shade: the picture will then be ever so much more bright. The great charm of a camera like this is to have a real and lifelike picture in natural colours spread out before you, to see still life as it stands, the trees waving in the wind, and flowers nodding in the sunshine, and every human being or animal that passes walking and moving on your plate.

SECTION VII.
THE BOY’S OWN WORKSHOP.