§ 9.—SCALES FROM REALISM TO CONVENTIONALISM.
These two methods, when applied absolutely, form the two extremes:—The most complete REALISM being at one end, and the most limited CONVENTIONALISM at the other. There are scales of gradual reduction between them, which may be shown on two charts:
(i) Reduction in the NUMBER OF PARTS which preserve their Realistic rendering.
(ii) Reduction in the DEGREE OF REALISM through all parts.
(i) According to the number of the features or parts of the design which are treated with less than realism. Thus there might be a panel representing a Window-opening with an architectural framing, with a Flower-vase on the sill, and a Landscape-background. The first part to be reduced in realistic rendering would be the Background, the second would be the Framing, leaving the third, the Flower-vase, as the survival. This is a Scale of reduction in Number of Parts.
It may be shown, in tabular arrangement, thus:—
| REALISM.........................................................CONVENTIONALISM. | |||
| COMPLETE PICTORIAL REALISM, in which all parts are realisticallyrepresented (see § 10). | SEMI-PICTORIAL REALISM, in which the Back-ground is reduced toa flat-tint, while all the remaining parts are realisticallyrepresented (see § 11). | DECORATIVE REALISM, in which the chief Feature (only)is realistically represented, and all the other parts arreduced to conventional renderings (see § 12). | COMPLETE CONVENTIONALISM, in which all parts are reduced toconventional renderings (see Conventionalism). |
Inasmuch as there is some realistic part remaining in each of the first three methods—these are classified under the heading of REALISM.
(ii) According to the Degree in which color, gradation, or shading, is sacrificed, in consequence of the limited Means at the disposal of the Artist; resulting in the gradual departure from Realism to the most severe Conventionalism. The reduction is applied to all parts of the work. This is a scale of reduction in Degree. There are two Varieties in each degree; and they are marked with italic letters.
It may be shown, in tabular arrangement, thus:—
| REALISM............................................................CONVENTIONALISM. | ||||
| COMPLETE REALISM, in which all parts are represented, inproper colors, and perfect gradation, with correct light andshade (see § 10). | FIRST DEGREE OF CONVENTIONALISM, in which all parts arerepresented: (a) By a reduced number of Pigments, the otherqualities remaining; (b) By reduction in gradation andshading to Flat-tints of several pigments (see § 15). | SECOND DEGREE OF CONVENTIONALISM, in which all parts arerepresented: (c) By a reduction to Monochrome of color, withGradation (only) remaining; (d) By reduction to Monochromeof White and Black, with Gradation (only) remaining (see §16). | THIRD DEGREE OF CONVENTIONALISM, in which all parts arerepresented: (e) By reduction to a Flat-tint of one pigmenton a ground of another; (f) By reduction to a Flat-tint ofWhite on Black, or vice versa (see § 17). | ULTIMATE CONVENTIONALISM, in which all parts arerepresented; (g) By reduction to Outline of severalpigments; (h) Reduction to Outline of one pigment (see §18). |
Inasmuch as Realism ceases so soon as any reduction in the three qualities (of color, gradation, and shadow) is introduced; and the treatment becomes more Conventional in each method after the first—these are classified under the heading of CONVENTIONALISM.
[There is an analogous scale of reduction in Form, from the Complete-relief of an isolated Statue to the Flatness of a Floor-plate; but this does not belong to the present subject.]
Lectures before the Society of Arts, London, 1891.
THE CYCLOSTAT.
The various processes commonly employed for the observation of bodies in motion (intermittent light or vision) greatly fatigue the observer, and, as a general thing, give only images, that are difficult to examine. We are going to show how Prof. Marc Thury, upon making researches in a new direction, has succeeded in constructing an apparatus that permits of the continuous observation of a body having a rapid rotary motion. The principle of the method is of extreme simplicity.
FIGS. 1, 2, AND 3.—DIAGRAMS EXPLANATORY OF THE PRINCIPLE OF THE CYCLOSTAT.
Let us consider (Fig. 1) a mirror, A B, reflecting an object, C D, and revolving around it: when the mirror will have made a half revolution, the image, C' D', of the object will have made an entire one. The figure represents three successive positions of the mirror, distant by an eighth of a revolution. The structure of the image shows that it has made a quarter revolution in an opposite direction in each of its positions. But if (Fig. 2) the body itself has revolved in the same direction with an angular velocity double that of the mirror, its image will have described a circle in remaining constantly parallel with itself. The image will be just as insensible as the object itself; but it is very easy to bring it back to a state of rest.
Let us suppose (Fig. 3a) the observer placed at O, the revolving object at T, the axis of rotation being this time the line O F. Let us place a mirror at A B and cause it to revolve around the same axis; but, instead of looking at the image directly in the mirror, let us receive it, before and after its reflection upon A B, upon two mirrors, C D and D E, inclined 30° upon the axis of rotation of the system; the image, instead of being observed directly in the mirror, A B, will always be seen in the axis, O F, and will consequently appear immovable.
The same result may be obtained (Fig. 3b) with a rectangular isosceles prism whose face, A B, serves as a mirror, while the faces, A C and B D, break the ray—the first deflecting it from the axis to throw it on the mirror, and the second throwing it back to the axis of rotation, which is at the same time the line of direction of the sight.
The principle of the instrument, then, consists in causing the revolution, around the axis of rotation of the object to be observed, of a mirror parallel with such axis, and in observing it in the axis itself after sending the image to it by two reflections or two refractions. In reality, the entire instrument is contained in the small prism above, properly mounted upon a wheel that may be revolved at will; and, in this form, it may serve, for example, to determine the rotary velocity of an inaccessible axis. For this it will suffice to modify its velocity until the axis appears to be at rest, and to apply the revolution counter to the wheel upon which the prism is mounted, or to another wheel controlling the mechanism.
But Mr. Thury has constructed a completer apparatus, the cyclostat (Fig. 4), which, opposite the prism, has a second plate whose actuating wheel is mounted upon the same axis as the first, the gearing being so calculated that the prism shall revolve with twice less velocity than the second plate. This latter, observed through the prism, will be always seen at rest, and be able to serve as a support for the object that it is desired to examine.
FIG. 4.—THE CYCLOSTAT.
1. General view of the apparatus.
2. Section of the ocular, O.
The applications are multitudinous. In the first place, in certain difficult cases, it may serve for the observation of a swinging thermometer, which is then read during its motion. Then it may be employed for the continuous observation of a body submitted to centrifugal force. Apropos of this, we desire to add a few words. Most of the forces at our disposal, applied to a body, are transmitted from molecule to molecule, and produce tension, crushing, etc. Gravity and magnetic attraction form an exception; their point of application is found in all the molecules of the body, and they produce pressures and slidings of a peculiar kind. But these forces are of a very limited magnitude; but it might nevertheless be of great interest to amplify them in a strong measure. Let us, for example, suppose that a magician has found a means of increasing the intensity of gravity tenfold in his laboratory. All the conditions of life would be modified to the extent of being unrecognizable. A living being borne in this space would remain small and squat. All objects would be stocky and be spread out in width or else be shattered. Viscid or semi-solid bodies, such as pitch, would rapidly spread out and take on a surface as plane and smooth as water under the conditions of gravity upon the earth. On still further increasing the gravity, we would see the soft metals behaving in the same way, and lead, copper and silver would in turn flow away. These metals, in fact, are perfectly moulded under a strong pressure, just like liquids, through the simple effect of the attraction of the earth applied to all their molecules. Upon causing an adequate attractive force to act upon the molecules of metals they will be placed under conditions analogous to those to which they are submitted in strong presses or in the mills that serve for coining money. The sole difference consists in the fact that the action of gravity is infinitely more regular, and purer, from a physical standpoint, than that of the press or coining mill. Through very simple considerations, we thus reach the principle which was enunciated, we believe, by the illustrious Stokes, that our idea of solid and liquid bodies is a necessary consequence of the intensity of gravity upon the earth. Upon a larger or smaller planet, a certain number of solid bodies would pass to a liquid state, or inversely. Let us return to the cyclostat. In default of gravity, centrifugal force gives us a means of realizing certain conditions that we would find in the laboratory of our magician. The cyclostat permits us to observe what is going on in that laboratory without submitting ourselves to forces that might cause us great annoyance. We have hitherto been content to put poor frogs therein and study upon them the effect of the central anæmia and peripheral congestion produced on their organism by the unrestrained motion of the liquids carried along by centrifugal force. The results, it seems, have proved very curious.—La Nature.
MERCURY WEIGHING MACHINE.
We illustrate herewith a novel type of weighing machine. Hitherto the weighing machines in common use have either been designed with some kind of steelyard apparatus, upon which weights could be moved to different distances from a fixed fulcrum, or springs have been so applied as to be compressed to different degrees by different weights put upon the scale pan, or table, of the machine. In other instances more complicated mechanism is used, and various movable counterpoises are usually required in order to balance the moving parts of the machine.
The type of machine which we now illustrate has been recently brought out by Mr. G.E. Rutter, and the system has given very satisfactory results with platform weighing machines. The engraving illustrates a form of balance which may be applied to strength testing machines, or for any work where an apparatus of the type of a Salter's balance would be of use. It is simple in construction, and consists of a tube A closed at the bottom and forming a reservoir for mercury. The body which it is required to weigh is hung upon the hook B carried by the crossbar C, which is connected by rigid rods to the upper part of the tube, and by means of the internal rods D is attached to the cross head E, which works freely inside the tube A. The top part of the tube is, as will be clearly understood from the illustration, cut away to allow of the descent of the rods. To the cross head E is attached the piston F, which may be made of wood or of a hollow metal tube closed at the end, or other suitable material. It will be easily understood that when a weight is hung upon the hook B, the piston F is caused to descend into the mercury which rises in the annular space between the piston and the tube. The weight of the volume of displaced mercury is proportional to the weight of the body hung upon the hook, and the buoyancy of the piston in the mercury forms the upward force which balances the downward pull of gravity. When the apparatus is at rest the piston F descends into the mercury to such a distance as will balance the weight of the rods, hook, and piston itself. If, now, the cross bar G, provided with a pointer H, be fixed to the rods, it should at that time register zero, upon the scale J fixed to the outside of the tube, and as the descent of the piston into the mercury is directly proportional to the weight of the body attached to the hook B, the divisions of the scale will all be equal. It will thus be seen that the apparatus is extremely simple in theory, and it only remains to construct it in such a form that the mercury may not easily be spilt in moving the instrument from place to place. This is effected by causing the cross head E to fill the tube while working freely therein, and a small valve is arranged to allow for the passage of air. The cross bar G can be regulated upon the rods by means of set screws.—Industries.
REEFING SAILS FROM THE DECK.
While this method may be applied to topsails and top-gallant-sails, I especially apply it to courses, which, being so difficult to reef the old way, may by this method be reefed from the deck in a few minutes.
After several years of trial by myself and others, on voyages around Cape Horn under all circumstances of weather, of sleet and snow, this method has always given the utmost satisfaction.
REEFING SAILS FROM THE DECK.
The average time required for reefing and setting was noted for five years, being seven and one-half minutes.
This trial was made on a mainsail, the yard being seventy-one feet long, and reefyard sixty-six feet long, eleven inches diameter at center and nine at yard-arms.
By reference to the drawing it will be seen that it is not necessary to have clewgarnets or buntlines in reefing. The operation is performed by easing of the sheet and hauling the lee reef-tackle first, also the midship reef tackle.
When the yardarm of the reefspar is up at the lee side, the sail cannot sag to leeward when the tack is eased away. Now haul the weather reef-tackle likewise midship, snug up to the yard, belay all down the tack, and sheet aft.
As all the reef-tackles lead to the slings of the yard, there is no impediment in swinging the yard when the reef-tackles are taut and belayed.
The slack sail will not chafe, as it remains quiet, but if so desired may be stopped up at leisure with only a few hands with stops provided for that purpose.
In case of a sudden squall the sail may be hauled up the usual way. The buntlines will draw the part of the sail below the reef well up on the part above the reefyard, and remain becalmed, while the weight of the reefspar will prevent any slatting or danger of losing the sail any more than any other sail clewed up.
In case there is steam power at hand, all three reef-tackles may be hauled simultaneously, easing sheet and tack sufficiently to let the wind out of the sail without shaking.
There are other advantages gained by this method; while its essentials are positive, quick reefing from the deck in all weathers, it is also better reefed than by the old method. For by this new method the sail is not strained or torn, and the sail will wear longer, not being subject to such straining.
It may be carried longer, as the spar supports the sail like a band, especially an old sail.
This method does not interfere with the use of the so called midship-tack, but change of putting on bands, from the leech of the sail at the reef to the center tack would be necessary.
The weight of the spar may be considered by some as objectionable, (an old argument against double-topsail yards). The spar used for the reef may be about one-half the diameter of the yard on which it is to be used.
Such critics do not consider that a crew of men aloft on the yard are several times heavier than such a spar.
L.K. MORSE.
Rockport, Me., Oct. 28, 1891.
A NEW PROCESS FOR THE BLEACHING OF JUTE.
By Messrs. LEYKAM and TOSEFOTHAL.
Jute is well known as a very cheap fiber, and its employment in textile industry is consequently both extensive and always increasing. Accompanying this increase is a corresponding one in the amount of old waste jute, which can be employed for the manufacture of paper.
Up to the present time, only very little use has been made of jute for the manufacture of thread and the finer fabrics, because the difficulty of bleaching the fiber satisfactorily has proved a very serious hindrance to its improvement by chemical means. All the methods hitherto proposed for bleaching jute are so costly that they can scarcely be made to pay; and, moreover, in many cases, the jute is scarcely bleached, and loses considerably in firmness and weight, owing to the large quantities of bleaching agents which have to be applied.
In consequence of this difficulty, the enormous quantities of jute scraps, which are always available, are utilized in paper making almost entirely for the production of ordinary wrapping paper, which is, at the best, of medium quality. In the well known work of Hoffmann and Muller, the authors refer to the great difficulty of bleaching jute, and therefore recommend that it be not used for making white papers.
Messrs. Leykam and Tosefothal have succeeded in bleaching it, and rendering the fiber perfectly white, by a new process, simple and cheap (which we describe below), so that their method can be very advantageously employed in the paper industry.
The jute fiber only loses very little of its original firmness and weight; but, on the other hand, gains largely in pliability and elasticity, so that the paper made from it is of great strength, and not only resists tearing, but especially crumpling and breaking.
The jute may be submitted to the process in any form whatever, either crude, in scraps, or as thread or tissue.
The material to be bleached is first treated with gaseous chlorine or chlorine water, in order to attack the jute pigment, which is very difficult to bleach, until it takes an orange shade. After having removed the acids, etc., formed by this treatment, the jute is placed in a weak alkaline bath, cold or hot, of caustic soda, caustic potash, caustic ammonia, quicklime, sodium or potassium carbonate, etc., or a mixture of several of these substances, which converts the greatest part of the jute pigment, already altered by the chlorine, into a form easily soluble in water, so that the pigment can be readily removed by a washing with water. After this washing the jute can be bleached as easily as any other vegetable fiber in the ordinary manner, by means of bleaching powder, etc., and an excellent fibrous material is obtained, which can be made use of with advantage in the textile and paper industries.
The application of the process may be illustrated by an example:
One hundred kilos. of waste jute scraps are first of all treated in the manner usually employed in the paper industry; 15 per cent. of quicklime is added, and they are treated for 10 hours at a pressure of 1½ atmospheres. The scraps are then freed from water by means of a hydro-extractor, or a press, and finally saturated with chlorine in a gas chamber for 24 hours or less, according to the requirements of the case. Every 100 kilos. of jute requires 75 kilos. of hydrochloric acid (20° B.) and 20 kilos. of manganese peroxide (78-80 per cent.).
The jute then takes an orange color, and is subsequently washed in a tank, a kilo. of caustic soda being added per 100 kilos. of jute; this amount of alkali is sufficient to dissolve the pigment, which colors the water flowing from the washer a deep brown. After washing, the jute can be completely bleached by the use of 5-7 kilos. of bleaching powder per 100 kilos. of jute.—Mon. de la Teinture.
THE INDEPENDENT—STORAGE OR PRIMARY BATTERY—SYSTEM OF ELECTRIC MOTIVE POWER.[1]
By KNIGHT NEFTEL.
Owing to a variety of causes, the system which was assigned to me at the last convention to report on has made less material progress in a commercial way than its competitors.