Chapter X (3)

As a wick, besides cotton, several substances have been recommended. The filaments of amianthus, for instance, while they perform the office of a wick, are incombustible. The _Journal de Verdun_ for 1748, announced incombustible wick by sieur Lespar. Touch wood, the _tussilago sarfara_, and the _verbascum tapsus_ of Linnæus, are also recommended. In 1783, Leger announced, in the _Journal de la Blancherie_, that he had invented a match which would burn without smoke and odour.

Lamps have been furnished with fixed and moveable mirrors, to throw the light forward by reflection. The reverberatory lamps, revolving lights for light houses, &c. are of this kind. Many patents have been obtained for such contrivances, which we have not room to notice.

The inflammable air lamp for the table, described in the _Dictionnaire de l'Industrie_, is nothing more than a spirit of wine lamp, and used in lieu of hot bricks, or vessels filled with boiling water for the warming of dishes, &c. In 1780, M. Ehrman, in his _Description et usage de quelques lampes à air inflammable_, describes a chafing dish with inflammable air, invented by Nevet, which operates by the combustion of hydrogen gas.[26]

Fixed illuminations are more brilliant and more magnificent; as the lights are more numerous, as well as more diversified. Wax, spermaceti, or tallow candles, or oil burnt in tin lamps, or in glass cups suspended by wire, are all used for the purpose. If the wick be dipped in spirit of turpentine, it will take fire instantaneously. It is unnecessary to make any remarks as to the arrangement of lights.

Large dishes containing melted tallow, and a wick proportionally thick and suspended by means of a simple contrivance of tin, are recommended for the same purpose. Coloured lights afford a variety. The appearance of coloured flame may be produced by burning the oil in coloured glasses, so disposed as to let the light pass through the glass, or by placing lamps behind bottles filled with coloured water.[27]

The coloured glasses which are sold in Paris for the purpose, are formed with facets on the outside, which not only produce the appearance of coloured flame, but also, according to the number of facets, the refraction and reflection of the light. Arches, pyramids, obelisks, &c. are lighted up in this manner.

The Pont Neuf, and the Seine in 1739, were illuminated at the time of the splendid exhibition of fire-works. It is unnecessary, however, to particularize on this head. We all remember the splendid illuminations in all our cities during the late war, which were indeed a true expression of our national and individual feeling. Illuminations, in this country, before that time were very rare; none we think since the peace of 1783, and the union under the federal compact.

Phosphuret of lime, of the size of peas, thrown into water, will afford, at short intervals, a brilliant flame of fire; for the phosphuretted hydrogen gas thus produced has the property of inflaming spontaneously in atmospheric air. Alcohol, containing sundry salts in solution, will give a flame of various colours, according to the salt it holds in solution. See _Alcohol_.

Illuminated works are much admired by the Italians, and particularly the _Illuminated chandelier_, which is considered a great addition to a collection of works. An illuminated chandelier is formed of thin wood with arms extending on each side. Holes are bored in the front of the branches and in the body, and also in the eagle (if it be added,) at top, and distant from each other about three inches. In these holes, we put illuminations, filled with white, blue and brilliant charge. Having fixed in the port-fires, they must be clothed with leaders, so that the chandelier and eagle may light together.

We may also observe, that, for the speedy lighting of a number of lamps, at one and the same time, quick-match enclosed in paper tubes has been used. This quick-match is sometimes made to communicate its fire to a sulphur match, prepared by dipping strands of cotton in melted sulphur, and from this to the lamp. Several methods are recommended for this purpose; one of which consists in dipping cotton wick in the oil of spike, and arranging it along the wicks of the different lamps, so that when inflamed the fire may pass rapidly from one lamp to another. In 1772, M. Renault, a Parisian, announced in the public papers, that he possessed a secret, by which he could light 2000 lamps in five minutes, by means of a match of communication.

We have some experiments and observations on coloured flame, by Mr. Morey, in his essay on heat and light, in the second volume of Silliman's _Journal of Science and Arts_, p. 120. The experiments are curious, and worthy of remark. If water, he observes, be put into one cylinder, and made to boil, and the steam be led to the bottom of another included cylinder, containing spirits of turpentine, the steam, when let out under a moderate pressure, carries off with it a sufficient quantity of the spirit to burn with a pleasant _white_ flame, free from smoke; but if the pressure be increased, the flame will become in part or wholly blue. "Here," he adds, "as in many other experiments, I have noticed, that different coloured flames may be produced from the same materials--are the products of combustion different?" He further observes, that "if the steam of water, containing a small proportion of the vapour of rosin, be driven against iron, at or below a red heat, it burns with a pleasant _blue_ flame, which will be extended some way back into the column of the vapour, intermixed with innumerable sparks of very white flame, evidently particles of the rosin. If the vapours, when the proportion of the rosin is very small, are made to pass between two plates of iron, at or near a red heat, they can be inflamed on the opposite sides of the plates, and will then, sometimes, burn with an entirely _blue_ flame, although the vapour can not be inflamed, without the intervention of the plates." He states other experiments, made with tallow and steam, producing a _blue_ flame. The _blue_ colour seems to be owing to the pressure made use of; for, in his second communication, (page 122, of the same volume), he mentions white flame being produced by the vapour of water; and when it is in a sufficient quantity, there is _no smoke_. If too great, combustion ceases. Speaking of the colour of the flame, produced by mixed vapours, (of the combustible and water), such as blue, blue and white, white and intense white, he adds, that they may be imitated, at pleasure, with the patent lamp stove, by burning tar, pitch pine, or mineral coal and water. Newly made charcoal will take up about three times its weight of water. "Sand, ashes, or fine clay," he observes, "answers well for mixing with the tar, &c. If the latter be made into a paste with equal parts of spirit of turpentine and water, and cold lumps of it, of a conical form, be placed on a table, and a flame applied, the vapours burn without smoke for a short time, &c. If enclosed in a tin cylinder, and the vapour be made to issue through small holes at the top, placed as before stated, or on a plate over a chafing dish of coals, it burns with a very bright light, free from smoke. If the cylinder be tight at the top and the vapour be led from the inside at the top, down and through the bottom, and there be made to issue in an oblique direction, and from a number of small openings, it will burn with a beautiful flame and supports and regulates, very accurately, its own evaporation. The oblique direction carries the heat, in part, beyond the cylinder, when the evaporation is too great.

"Every effect may be produced in consuming the smoke, and giving an intense white flame, by using a certain proportion of water, intimately blended or mixed with these vapours, that can be from an access of oxygen furnished, by creating a very strong current of air, with a high flue." The description of Morey's lamp stove, may be seen in the same work. The steam, he observes, may be furnished by a small tin boiler, and directed to or near the bottom of the tar. An _intense white flame free from smoke_, may be thus produced from tar, rosin, rough turpentine or the spirit, alcohol, oil, fat, tallow, mineral coal, pitch pine wood, and the knots, birch bark, and pumpkin, sun-flower, flax, and other seeds. With regard to pine wood, he adds, it is the easiest managed, evaporates at a lower temperature, consumes a greater proportion of water in its combustion, contains the water within itself, and gives a brighter light than common candles or lamps, and without smoke. The more volatile parts are evaporated at a temperature below that of boiling water, and burn well with three parts of the vapour of water; the flame then, however, is nearly _blue_. Observations on the application of this mode of producing light and heat, may be seen in Silliman, p. 131, &c. It appears, that Gay-Lussac (_Annales de Chimie_, for June, 1819,) has commented on Mr. Morey's plan.

Professor Hare (_Silliman's Journal_, vol. 2d, p. 172) also observes, that the flame of hydrogen gas is rendered luminous, like that of oil, by adding a small quantity of oil of turpentine to the usual mixture for generating this gas; and that the addition of 1/17 of the same fluid to alcohol, will give it the property of burning with a highly luminous flame; and there is a certain point in the proportions, at which the mixture burns without smoke, like a gas light. In the first instance, he observes, when the ingredients are at the proper temperature, the light is greater than that produced by carburetted hydrogen gas. Speaking of this application of spirits, the professor judiciously adds: "It might be serviceable to _morals_, if the value of this article could be enhanced by _a new_ mode of consumption." We find, also, that the effect of vapour on flame has been noticed by Dr. Dana, in the same Journal, vol. 1, p. 40; by which it appears, that when a jet of steam is made to pass into a charcoal fire, the vividness of the combustion is increased, and also the low attenuated flame of the coal; that it prevents the smoke of a common oil lamp, and makes the flame brighter; that the flame of spirit of turpentine, which is usually dull and reddish, is rendered bright, and no smoke is formed; or when the vapour of both are made to issue together from the same orifice, and inflamed, no smoke appears; that a jet of steam, thrown into the flame of a spirit of wine lamp, or into flames which evolve no smoke or carbonaceous matter, produces the same effect as a current of air; but that, in all flames which evolve smoke, steam produces an increased brightness and a more perfect combustion. Dr. Dana further suggests, that steam might be introduced into the flames of street lamps, which might be so contrived as to keep water boiling, to produce the steam, and thereby cause a more perfect combustion, and a greater quantity of light from the same materials.

Count Rumford has shown, that the quantity of light, emitted by a given portion of inflammable matter in combustion, is proportional, in some high ratio, to the elevation of temperature; and that a lamp, having many wicks near each other, so as mutually to increase their heat, burns with infinitely more brilliancy than the Argand lamps in common use. To measure the proportional intensities of two or more lights; place them a few inches asunder, and at the distance of a few feet or yards from a screen of white paper, or a white wall. On holding a small card near the wall two shadows will be projected on it, the darker one by the interception of the brighter light, and the lighter shadow, by the interception of the duller light. Bring the fainter light nearer to the card, or remove the brighter one further from it, till both shadows acquire the same intensity. Measure now the distances of the two lights, from the wall or screen, square them, and you have the ratio of illumination. Thus, if an Argand flame and a candle, stand at the distances of 10 feet and 4 feet, respectively, when their shadows are equally deep, we have 10^2 and 4^2, or 100 and 16, or 6-1/4 and 1, for their relative quantities of light.

The author of the _Dictionnaire de l'Industrie_, vol. iii, p. 365, in treating on the subject of illumination, mentions different modes of illuminating, both with and without transparencies. We know that various mixtures will produce different coloured flame. Thus, arsenic will burn with a beautiful white flame in oxygen gas; iron and steel will burn also, affording a brilliant light; phosphorus and charcoal with a white, and sulphur with a beautiful blue flame; zinc with a green colour, &c.

Again, we know that a mixture of nitrate of strontia and charcoal will burn with a rose coloured flame; one part of boracic acid, and three of charcoal, with a green flame; one of nitrate of barytes, and four of charcoal, with a yellow flame; and equal parts of nitrate of lime and charcoal powder, with an orange flame. We also know, that cotton dipt in oil of turpentine, or ardent spirit, rosin, camphor, &c. will burn extremely vivid and beautiful.

The author, whom we have just quoted, gives some remarks on the various coloured flames, that may interest the reader.

_Felt_ (_Feutre_, Fr.) he remarks, if put in the fire, will give most beautiful colours, a golden yellow and a brilliant blue. And this, he adds, may be proved by throwing pieces of old hats into the fire; for these colours depend on the substances used in dying the hat. He further remarks, that green oak wood gives a yellow flame, and alcohol with sedative salt, (boracic acid), a blue, and that, by uniting the flame of both, the product, as to colour, will be a green.

The flame of alcohol is changed of various colours, according to the salt it holds in solution. Of this circumstance, Schatt was apprised, when he gave some formula many years ago, on the manner of forming coloured flame. Reaumur remarked also, the different colours which some metals assume, when submitted to the action of heat, which is known now to be the effect of oxidizement.

As respects the phenomena with felt, we are told, that, if we throw into the fire the cuttings of hats, we will perceive at first a white flame, and then in succession a blue, green, and violet colour; all which, our author observes, proceeds from the verdigris and other substances, employed in the composition of the dye stuff. There is one fact, which he has asserted, which may probably be explained on the _materiality_ of light, so far as regards the _formation_ of colour, (not considering, however, the theory of Bancroft, given in his _Philosophy of Permanent Colours_, or the more philosophical one of Dr. Samuel Conover, of Philadelphia, in the Transactions of the _American Philosophical Society_), and this fact is, that the flame carries the colour to the object which it illuminates, and that the object itself actually partakes of the colour, in order to produce any particular appearance. That colours, as visible to the eye, are all formed in the solar light, and their appearance depends upon the _absorption_ of some of the rays of light, and the _reflection_ of others, is a doctrine which followed the discoveries of Sir Isaac Newton. We have not room to notice this subject, however interesting it may be in a philosophical point of view.

There can be no doubt, that the art of colouring flame was known for a long time. We are told, that the philosopher Anaxilaus even pretended, that, by putting ink with the oil of a lamp, or the liquor of the cuttle fish, the faces of the bystanders will appear _black_ by the light of this lamp! Sulphur has the effect of rendering the visage pale and cadaverous. Other persons, as Simon Sethe, advanced an opinion, that, if we moisten the wick of a lamp with ink, or in a mixture of the rust of copper, and having lighted the wick, and placed other lights around it, the faces will appear, some black, and some of a brass colour. Others, such as Cardan, say, that, by making a mixture of wine and salt, and then reducing it two-thirds by evaporation, the flame, which the wine will then give, will make the _living_ put on a cadaverous appearance, if they remain in one posture. Malina also observes, that, by burning a piece of woollen cloth well soaked in a solution of salt in vinegar, the visage will appear frightful by the light of the flame. But the process of J. B. Porta is not less worthy of note. If good old wine, he observes, be put into a bowl with a handful of salt, and set on live coals, but not in the flame, and as soon as it begins to boil, is set on fire, (the other lights in the room being extinguished), the figure of each person will appear so hideous, as to produce a mutual dread. The author of the _Dictionnaire de l'Industrie_, iii, p. 433, observes, that he has repeated this experiment, sometimes with brandy, and at other times with alcohol, with perfect success.

A cadaverous appearance is said to be given, by mixing common salt with alcohol, in which some saffron had been infused. When set on fire, and the other lights extinguished, the effect, we are told, is very striking.

The so called _miraculous luminaries_, are nothing else than solar phosphori, which are very numerous. Their effect is to emit light in the dark, but not heat. Almost every thing in nature possesses this property in a greater or less degree, which depends on the absorption and subsequent transmission of light. The eyes of various animals have this property; cats and owls in particular. Snow possesses it in a considerable degree. Putrid animal matter, fish, for example, rotten wood, &c. partake also of this property.

It may not be improper to notice, in a general way, some of the substances, which are denominated solar phosphori. The _Bolognian phosphorus_ is the calcined baroselenite, (sulphate of barytes), which, when exposed a few minutes to the light, shines when taken into the dark like burning coals. In water it emits the same light. This property, as is the case with all other solar phosphori, it loses gradually; but by heating it again, imbibes light. _Canton's phosphorus_ is calcined oyster shells. It is used in the same manner. _Baldwin's phosphorus_ is fused nitrate of lime. Various saline and other bodies, as diamonds and precious gems, possess the same property. Expressed oils and animal fats, when heated to 450°, become phosphorescent.

Hanzelet (_Traité des Feux d'Artifice_) remarks, that a _stone_ may be made to give light by water, if prepared in the following manner. Take quicklime, tutty, and saltpetre, of each one part; reduce them to powder, and expose them to the action of heat. On the addition of water, light is said to be given out.

When quicklime is mixed with essential oil, and brought in contact with water, spontaneous combustion is said to take place.

Fluor or Derbyshire spar, (fluate of lime), when pulverized and heated to 212° Fahr., and then removed to the dark, is very luminous. If writing be made on a copper or iron plate, with thin mucilage or white of egg, and powdered fluor spar, sprinkled on it; when the plate is removed to a gentle coal fire, the delineated objects will become luminous, and opaque again when the plate becomes cold. The lapis lazuli has the same effect.

The phosphoric substances, which become luminous by attrition or percussion, are numerous. _Homberg's phosphorus_, which is nothing more than calcined muriate of lime, is of this character. When struck it emits light. Without either light or fire, a number of bodies will give out light. Flints, and other siliceous stones, struck against one another, appear luminous in the dark. Various other minerals have the same property. Wedgwood (_Phil. Trans._ 179,) Coates (_Nich. Jour._ 1799,) Westrumb (_Crell's Chem. Annals_, 1784,) have written on this subject; to which enumeration we may add the interesting remarks of Dr. Hulme, (_Phil. Trans._ 1800,) and the observations of Cabarris, in his Memoir, read before the National Institute.

It may be sufficient to remark, that the shell-fish called _pholas_; the _meduca_ phosphorea, and other _molluscsæ_; several insects of the species _fulgora_, or lantern-fly; the _lampyris_, or glowworm; the _scolopendra electrica_; the _cancer fulgens_; the medullary substance of the human brain, &c. are all phosphorescent.

M. Dessaignes (_Bulletin de la Société Philomatique, Octobre_, 1810) made a number of experiments on solid, liquid, and aeriform bodies, relative to the disengagement of light by compression. Among other conclusions, he adds, that water is the cause of the spontaneous phosphorescence of bodies, such as quicklime, Canton's phosphorus, dry muriate of lime, &c. all which, when brought in contact with water, emit light, which he attributes to the consolidation of that fluid. The absorption of moisture, and its subsequent consolidation, may, in some instances, give rise to luminous appearances.

The _lapis solaris_, Bolognian stone, or the present sulphate of barytes, was discovered in 1602, by Casciorolus, a shoemaker of Bologna. He came to Scipio Begatello, who at that time was particularly known by his attachment to the art of gold-making, and showed him this stone, under the mystical name of _lapis solaris_, on account of its attracting the _golden_ light of the sun, and its boasted fitness for converting the _semi-metals_ into gold, the _sol_ of the alchemists!

Dr. Brewster (_Edinburgh Philosophical Journal_) made a number of experiments on the colour and intensity of light, evolved by different minerals, by which it appears, that the yellow sulphate of barytes gives a pale light, while fluate of lime, a blue and green light. Cellini (_Treatise on Jewelry_, published near the beginning of the 16th century) was the first who observed the phosphorescence of minerals; it does not appear that he knew of the Bolognian stone. Grimshire (_Nicholson's Journal_, 8vo. vols. 15, 16, 19,) made a number of experiments on the emission of light by bodies, when subjected to the electrical influence; and, when thus treated, sulphate of barytes gave a brilliant green light.

The _cawk_ of the miners, as it is also a sulphate of barytes, phosphoresces when previously exposed to heat.

There are two water fountains, both set in motion by the action of heat on confined air, which, as it expands, forces the water from an under vessel in jets. The first is called the _illuminated fountain_, and plays when the candles are lighted, stopping when they are extinguished. The other is a fountain, which acts on the same principle, but by the heat of the sun. The effect of the first is more or less considerable according to the pressure of the air upon the water, and consequently, to the degree of rarefaction which the air undergoes.

The _chemical illumination_ of some writers, by using oil of vitriol, iron filings, and water, and inflaming the vapour as it proceeds from a bottle, is nothing else than the inflammation of hydrogen gas. The "white vapours," which they describe, is the gas in question.

Having noticed the use of candles and lamps for illumination, we purpose, in concluding this article, to give the result of some experiments on the relative intensities of light, and duration of different candles, made by Dr. Ure, which we extract from his _Dictionary of Chemistry_.

----------+----------+---------+----------+---------+---------+---------
Number | Duration | Weight | Consump. | Propor- | Economy | Candles
in a | of a | in | per hour:| tion of| of |equal one
pound. | candle. | grains. | grains. | light. | light. | argand.
----------+----------+---------+----------+---------+---------+---------
10 mould | 5 h. 9 m.| 682 | 132 | 12¼ | 68 | 5.7
10 dipped | 4 36 | 672 | 150 | 13 | 65½ | 5.25
8 mould | 6 31 | 856 | 132 | 10½ | 59½ | 6.6
6 do. | 7 2½ | 1160 | 163 | 14⅔ | 66 | 5.0
4 do. | 9 36 | 1787 | 186 | 20¼ | 80 | 3.5
Argand | | | | | |
Oil Flame | | | 512 | 69.4 | 100 |
----------+----------+---------+----------+---------+---------+---------

The doctor remarks, that 1/8th of a gallon of good seal-oil, weighs 6010 gr. or 13 and 1/10th oz. avoirdupois, and lasts, in a bright argand lamp, 11 hours 44 minutes. The weight of oil it consumes per hour, is equal to four times the weight of tallow in candles, 8 to the pound, and three and one-seventh times the weight of tallow in candles, 6 to the pound. But its light being equal to that of 5 of the latter candles, it appears, from the above table, that 2 lbs. weight of oil, in an argand, are equivalent, in illuminating power, to three pounds of tallow candles. The larger the flames in the above candles the greater the economy of light.[28]

_Sec. XXIX. Of Imitative Fire-Works._

Imitative fire-works are nearly of the same character as the transparencies and illuminations mentioned in the last section; but, as this subject may be interesting to some of our readers, we thought proper for that reason to appropriate a section to its consideration.

Imitative fire-works are formed in the following manner: Take a paper that is blacked on both sides, or instead of black, let it be coloured on each side with a deep blue, which will be still better for such as are to be seen through transparent papers. It must be of a proper size for the figure intended to be exhibited. In this paper, cut with a pen-knife several spaces, and with a piercer make a great number of holes, rather long than round, and at no regular distance from each other.

To represent revolving pyramids and globes, the paper must be cut through with a pen-knife, and the space cut out between each spiral should be three or four times as wide as the spirals themselves. They must be so cut, that the pyramid or globe may appear to turn on its axis. The columns that are represented in pieces of architecture, or in jets of fire, must be cut in the same manner as if they are to be represented as turning on their axis.

In like manner may be exhibited a great variety of ornaments, cyphers, and medallions, which, when properly coloured, cannot fail of producing a most pleasing effect. There should not be a very great diversity of colours, as that would not produce the most agreeable appearance.

When these pieces are drawn upon a large scale, the architecture or ornaments may be shaded; and to represent different shades, pieces of coloured paper must be pasted over each other, which will produce an effect that would not be expected from transparent paintings. Five or six pieces of paper, pasted over each other, will be sufficient to represent the strongest shades. To give these pieces the different motions they require, we must first consider the nature of each piece: if, for example, we have cut out the figure of the sun, or of a star, we must construct a wire wheel of the same diameter with those pieces. Over this wheel a very thin paper is to be pasted, on which is drawn with black ink the spiral figure. The wheel thus prepared, is to be placed behind the sun or star, in such a manner that its axis may be exactly opposite the centre of either of those figures. This wheel may be turned by any contrivance.

Now, the wheel being placed directly behind the sun, for example, and very near to it, is to be turned regularly round and strongly illuminated by candles placed behind it. The lines that form the spiral will then appear through the spaces cut from the sun, to proceed from its centre to its circumference; and will resemble sparks of fire that incessantly succeed each other. The same effect will be produced by the star, or by any other figure, where the fire is not to appear as proceeding from the circumference to the centre.

These two pieces, as well as those that follow, may be of any size, provided we observe the proportion between the parts of the figure and the spiral, which must be wider in large figures than in small. If the sun, for example, have from six to twelve inches diameter, the width of the strokes that form the spiral need not be more than one-twentieth part of an inch, and the spaces between them that form the transparent parts, about two-tenths of an inch. If the sun be two feet in diameter, the strokes should be one-eighth of an inch, and the space between, one quarter of an inch; and if the figure be six feet in diameter, the strokes should be one-fourth of an inch, and the spaces, five-twelfths of an inch. These pieces have a pleasing effect, when represented of a small size; but the deception is more striking when they are of larger dimensions.

It will be proper to place these pieces, when of a small size, in a box quite close on every side, that none of the light may be diffused in the chamber; for which purpose it will be convenient to have a tin door behind the box, to which the candlesticks may be soldered, and the candles more easily lighted.

The several figures cut out should be placed in frames, that they may be put alternately in a groove in the forepart of the box, or there may be two grooves, that the second piece may be put in before the first is taken out.

The wheel must be carefully concealed from the eye of the spectator. Where there is an opportunity of representing these artificial fires by a hole in the partition, they will doubtless have a much more striking effect, as the spectator cannot then conjecture by what means they are produced.

It is easy to conceive, that, by extending this method, wheels may be constructed with three or four spirals, to which may be given different directions. It is manifest, also, that, on the same principle, a great variety of transparent figures may be contrived, which may be all placed before the same spiral lines.

In representing cascades of fire, it is necessary to observe, that, in cutting out the cascades, care must be taken to preserve a natural inequality in the parts cut out; for if to save time, all the holes are made with the same pointed tool, the uniformity of the parts will produce a disagreeable effect.

To produce the apparent motion of these cascades, instead of drawing a spiral, a slip of strong paper is to be provided, in which there must be made a great number of holes near each other, and made with pointed tools of different dimensions.

At each end of the paper, a part, of the same size with the cascade, must be left uncut; and towards those parts the holes must be made a greater distance from each other.

When the cascade that is cut out is placed before the scroll of paper just mentioned, and it is entirely wound upon the roller, the part of the paper that is then between, being quite opaque, no part of the cascade will be visible; but, as the wheel is turned gently and regularly round, the transparent part of the paper will give to the cascade the appearance of fire that descends in the same direction; and the illusion will be so strong, as to appear as a real cascade of fire.