A Select Collection of Valuable and Curious Arts and Interesting Experiments Part 3

90. TO GIVE LEATHER A BEAUTIFUL METALLIC l.u.s.tRE.--Levigate one ounce of soft lead-coloured plumbago, and an equal quant.i.ty (in bulk) of lamp-black, in a gill of alcohol; then add half an ounce of loaf sugar, moistened with water and grind all together. The leather must first be brushed over smoothly with this composition, and when dry, it must be brushed hard and quickly with a dry smooth brush; or may be rubbed with a piece of woollen cloth. This blacking will be found useful for some ornamental purposes, but may be rather too brilliant for boots and shoes. This composition, however, may be mixed occasionally with other kinds of blacking, and will tend to increase their brightness.

91. AN EASY METHOD OF EXTRACTING THE ESSENCE OF ROSES.--Take the leaves of roses, and pound or bruise them: then stratify them with an equal weight of muriate of soda, in a glazed earthern vessel:--when thus filled to the top, cover it well, and set it in the cellar, and let it remain at rest a month or more. Afterwards, strain off the essence therefrom, through a strong cloth by pressure. The essence thus procured, is quite equal if not superior for culinary purposes, to that which is procured by distillation.

92. TO PREPARE VARIOUS KINDS OF ESSENCES.--The manner of extracting the essential oils, being attended with considerable expense of preparations, of stills, &c. a particular description of the process, would not, it is presumed, be sufficiently interesting to warrant its insertion. But the manner of reducing the oils to the state in which they are more generally sold, and is distinguished by the term "essences" is as follows. To half a pint of alcohol, add one ounce of any of the essential oils, (lemon, cinnamon, foxberry, peppermint, &c.) and shake them together; set the mixture in a warm place for a few minutes, and if then any opaque or milky appearance remains, a little more alcohol must be added. When this has become clear, it may be diluted occasionally with new rum. The essences of foxberry and cinnamon are coloured with a few drops of tincture of red saunders; and the essence of lemon, with tincture of turmeric.

93. TO PREPARE SODA WATER.--Only two articles are requisite for this preparation; one of which is super-carbonate of soda, or of pota.s.s (sal eratus,) and the other is citric or tartaric acid. The super-carbonates are formed by pa.s.sing a stream of carbonic acid gas (which is produced by adding muriatic acid to pulverized marble) through a solution of soda or pota.s.s in water;--then evaporating till it crystallizes. Citric acid is prepared from the juice of lemons; and tartaric acid (which is more generally employed) is procured from super-tartrate of pota.s.s. But these being common articles of commerce, a more minute description of the process of preparing them, may not, in this place, be expedient. The compound called soda powders, consists of about ten grains of either of the super-carbonates, with an equal quant.i.ty of either of the acids, in each paper; this compound being dissolved in a gla.s.s of water, produces violent effervescence, and if drank off at the time, gives the water a smart and agreeable acid taste. The salt and acid, if mixed in powder, must be kept perfectly dry; otherwise, they would act on each other, and soon be spoiled. On this account, they are frequently prepared in separate papers, and sold by sets. Soda water is similarly prepared on the larger scale; the salts and acid being put into a cask of water, which is so confined, that the carbonic acid can have no other vent than by forcing out the water through a pipe fixed for the purpose with a tube, &c.

94. TO PRODUCE METALLIC TREES. _Process 1._--Mix one part of a saturated solution of nitrate of silver, with twenty parts of pure water, and pour the mixture upon two parts of mercury in a phial.

After some time (the mercury being left standing quietly,) the branches and the figure of a tree, formed of brilliant silver, will appear to grow from the mercury in a very beautiful manner. The silver in solution being thus robbed of its oxygen by the metallic mercury, and consequently precipitated.

95. _Process 2._--Dissolve two drachms of acetate of lead, in six ounces of water; filter the solution, and pour it into a clean wide phial. Then suspend a granule of zinc, by a thread or wire fastened to the cork of the phial, in the middle of the solution, and place the phial where it will not be disturbed. After a few hours the lead, being de-oxydized by the zinc, will be precipitated on the zinc, in the shape of leaves, which will have a very brilliant appearance.

96. TO TIN COPPER BY BOILING.--Boil half a pound of granulated tin, and six ounces of super tartrate of pota.s.s in three pints of water; when they have boiled half an hour, put in any piece of copper ware, and continue the boiling fifteen minutes longer. The copper may then be taken out, and will have been handsomely coated with tin.

97. A METAL THAT WILL MELT IN HOT WATER.--Melt together eight parts of bis.m.u.th, five of lead and three of tin. This alloy, though hard and brilliant, when cold, is so easily fusible that it may be melted on a paper, being held over the flame of a candle. Tea spoons may be made of this compound metal, which may be melted by putting them in a cup of hot tea.

98. ILl.u.s.tRATION OF CALICO PRINTING.--It frequently occurs, that substances of different colours, or even without colour, by coming in contact, produce colours very different from that of either of the ingredients when separate; thus, if a sheet of paper be striped in one direction with a hair pencil dipped in a solution of sub-carbonate of pota.s.s; and then crossed with a solution of sulphuric acid, diluted with five times as much water, it will be colourless; but dip it in a mixture of a weak solution of sulphate of iron, and infusion of nut galls, and it will instantly become a beautiful plaid; the ground being purple, striped one way with black and crossed with white. If a similar paper be striped with sub-carbonate of pota.s.s, and crossed with infusion of galls, and afterward dipped in a solution of sulphate of iron, it will become purple, yellow, black and white. Dip a piece of white calico in a cold solution of sulphate of iron and let it dry.

Then imprint any figures upon it with a strong solution of colourless citric acid, and let this dry also. If the piece be then well washed in warm water, and afterwards boiled in a decoction of log-wood, the ground will be dyed either a slate or a black colour, according to the strength of the metallic solution, while the printed figures will remain beautifully white. Stain some parts of a sheet of paper a purple brown, with a mixture of infusion of galls and sulphate of iron; stain other parts green with a mixture of tinctures of turmeric and litmus; stain other parts purple with juice of red cabbage; other parts red with tincture of litmus and muriatic acid; other parts yellow with tincture of turmeric; wash the remainder of the sheet with a solution of sulphate of iron, which will remain white. Then print, or draw with a camel-hair pencil, any figure or figures on every part of the paper, with a solution of sub-carbonate of pota.s.s. On the purple brown, the figure will be black; on the green it will be purple; on the purple it will be green; on the red it will be blue; on the yellow, red; and on the white, it will take a yellow colour. Thus the figure will appear in colors different from the ground in every part. Immerse a piece of white cotton in a solution of sulphate of iron--it will remain white; dip another piece in tincture of turmeric, it will take a yellow; wet another piece with juice of red cabbage, containing also, a few drops of muriatic acid,--it will be red; dye another piece green, by immersing it in a mixture of tincture of turmeric and litmus; and another, purple by a mixture of infusion of galls and sulphate of iron. Let them dry; then immerse them all together in a solution of sub-carbonate of pota.s.s. The white will be changed to a yellow; the yellow to a red; the red to green; the green to purple; and the purple to black; and it is not improbable that some black might be materially changed or bleached by the same simple solution.

99. TO PREPARE AN IMITATION OF GOLD BRONZE.--Melt two ounces of tin, and mix with it one ounce of mercury; when this is cold pulverize it and add one ounce of muriate of ammonia, and one ounce of sulphur, and grind them all together. Put the compound in a flask and heat it in a clear fire (carefully avoiding the fumes) till the mercury sublimes, and rises in vapour. When the vapour ceases to rise, take the gla.s.s from the fire. A flaky gold colored powder will remain in the flask, which may be applied to ornamental work in the manner of gold bronze, of which it is a tolerable imitation.

100. TO PROCURE THE EXHILARATING GAS.--Put a quant.i.ty of nitrate of ammonia into a flask, and apply the heat of a lamp, which must be gentle, and well regulated. The salt will in a short time liquify, and must then be kept quietly simmering, avoiding violent ebullition. The gas will be evolved, and rise through the neck of the flask, and may be collected in a bladder containing a small quant.i.ty of water, and should be allowed to stand a few hours, and s.h.i.+fted into another bladder, or silk varnished bag before it is used. Though this gas is not fitted to support life, yet it may be respired for a short time, and the effects produced by it upon the animal frame, are its most extraordinary properties. The effects of this gas, are in general, highly pleasurable, and resemble those attendant on the agreeable period of intoxication. Exquisite sensations of pleasure; an irresistible propensity to laughter; a rapid flow of vivid ideas; a strong incitement to muscular motion, are the ordinary feelings produced by it. And what is exceedingly remarkable, is, that the intoxication thus produced, instead of being succeeded by the debility subsequent to intoxication by ardent spirits, does, on the contrary, generally render the person who takes it, cheerful and high spirited for the remainder of the day.

101. CONSTRUCTION OF A GALVANIC PILE OR BATTERY.--Procure fifty or more thin plates of copper, and the same number of plates of zinc, all of which may be about the size of a dollar, but not so thick. The copper and zinc plates, may be either cast in moulds, or may be cut out of rolled plates of the metals. In addition to the plates of copper and zinc, it is necessary to be provided with an equal number of pieces of woollen cloth, rather smaller than the metallick plates in size. Let these be soaked in a solution of muriate of soda, till they have thoroughly imbibed it; then take them out of the solution, and squeeze them gently, to force out the superabundant water. Then, having provided a circular piece of wood, rather larger than the plates, cover it with tin foil, and on this lay a plate of zinc, upon that a plate of copper, and then a piece of moistened cloth; next a plate of zinc, &c. Continue this arrangement of zinc, copper and cloth, till all the pieces that have been provided are laid on. As the pile began with zinc, it must be concluded with copper. This pile may be braced occasionally with strips of gla.s.s to prevent its being overthrown, Fix the end of a piece of metallic wire, in contact with the base, and lay the end of another piece upon the top of the pile; if thus, the opposite ends of the wire be brought in contact with each other, or if they are connected by any conducting body, so as to form a circuit of conductors, the pile will afford a constant and powerful current of the galvanic fluid through them for many hours. If the hands be moistened, and one of them applied to each of the wires, a shock will be received. Gold and other metals have been melted, and even burnt; and pota.s.s, soda and lime have been reduced to their respective metallic states, by being made to form part of a galvanic circuit. When the pile is not in use, it should be taken down, which will preserve it from wear, and the plates will require to be cleansed occasionally, which may be easily done by diluted muriatic acid.

102. CONSTRUCTION OF THE OXY-HYDROGEN BLOW-PIPE.--This useful instrument consists of a cubical vessel, made of tin plate, being from ten to twenty inches in length, breadth and height. The inside is divided into four equal apartments, by two part.i.tions, crossing each other in the centre. The two front apartments are covered at the top, and each of them have a tube fixed in the front side, near the top, with a stopc.o.c.k. The other apartments are open at the top, and communicate with those in front, by a small aperture near the bottom of each. These apartments being all filled with water, those in front are filled, the one with oxygen, and the other with hydrogen gas, which is done by forcing the gases into them through the tubes in front, which causes the water to recede through the aperture at the bottom, and consequently, part of the water is forced over the top of the other apartments; or rather, may run off through small tubes, fixed for the purpose, near the top, similar to those in front. When the front apartments are filled with the gases, (which may be known by the bubbling in the others) the tubes are stopped, and two leaden pipes are fixed in them, the opposite ends of which, are so placed, that the two streams of gas, when expelled from the gas holders, may come in contact very near the ends of the pipes. When the tubes are open, the pressure of the water will expel the gases, and will consequently settle, and must be replenished, so as to keep the apartments nearly full. When the two streams of gas are ignited at the point of contact, a flame is produced of sufficient intensity to burn gold, silver, copper or tin, with a very brilliant combustion.

103. TO MAKE A DRY PHOSPh.o.r.eSCENT POWDER.--Take some thick oyster sh.e.l.ls, wash them, and calcine by keeping them red hot in an open fire for half an hour: then, select the clearest and whitest parts, and reduce them to powder. Mix three parts of this powder, with one of the flour of sulphur; fill a crucible with this compound, pressing or beating it down as hard and solid as may be, without breaking the crucible. Set the crucible in the fire, and heat it moderately at first, but increase the heat gradually for an hour, in which time it must approach nearly to a white heat. Then let it cool, and again select from the ma.s.s, the whitest and purest parts, which must be preserved in a phial with a gla.s.s stopper. This powder has the peculiar property of imbibing the rays of the sun in the day time, and emitting them again in the night; or if the phial containing it, be exposed for a few minutes to the direct rays of the sun and then carried into a dark room, light enough will be evolved to render it distinctly visible.

104. CURIOUS EXPERIMENT OF PRECIPITATION.--Set five gla.s.ses on the table, and nearly fill one of them with a solution of sulphate of iron; and another with a solution of sulphate of copper; a third with a solution of nitrate of bis.m.u.th; pour into the fourth, a solution of nitro-muriate of cobalt, and into the fifth a solution of acetate of lead, or sulphate of zinc. These liquid solutions may all be diluted so as to be colourless. Then pour into each gla.s.s, a few drops of a colourless solution of prussiate of pota.s.s. The contents of the first gla.s.s will be instantly changed to a full blue colour; those of the second to a reddish brown; those of the third, to a yellow; the fourth to a green, and the fifth to a white. Thus five distinct colours will be given, by the addition of one colourless solution.

105. TO MAKE A BEAUTIFUL SOFT GLa.s.s FOR JEWELRY.--Take six ounces of clean fine white sand, three ounces of red lead, three ounces of pure sub-carbonate of pota.s.s, one ounce of nitrate of pota.s.s, half an ounce of borate of soda, and two drachms of a.r.s.enic; mix and pound them all together. Put the compound in a crucible, and set it in a common fire, often stirring it with an iron rod, till it is well melted, and becomes transparent. This compound will liquify very easily without any great heat, if the sand is fine, (which sometimes requires to be ground or pounded in a gla.s.s or flint mortar,) and if it be kept melted awhile, will become beautifully transparent, and may be cast or blown in the manner of other gla.s.s. This gla.s.s may be changed to a red or ruby colour, by adding and fusing together with it, a small quant.i.ty of finely powdered precipitate of gold, (gold precipitated from solution in nitro-muriatic acid by the addition of tin.) It may be also changed to blue by the addition of zaffre, (an ore of cobalt,) and magnesia: a green colour may be given by a precipitate of copper; and yellow by calcined iron, and white by calcined bones. This subject is treated of largely in the _Handmaid of the Arts_, to which, for further information on the subject, the reader is referred.

106. COMPOSITION OF VARIOUS KINDS OF GLa.s.s.--The best flint gla.s.s is composed of 129 lbs. of white sand, 50 lbs. of red lead, 40 lbs. of sub-carbonate of pota.s.s, 20 lbs. of nitrate of pota.s.s, and 5 oz. of magnesia. The best crown gla.s.s is composed of 60 lbs. of white sand, 30 lbs. of sub-carbonate of pota.s.s, 15 lbs. of nitrate of pota.s.s, 1 lb. of borate of soda and 1/2 lb. of a.r.s.enic. The composition of common green window gla.s.s, is 120 lbs. of white sand, 30 lbs. of sub-carbonate of pota.s.s, 60 lbs. of wood ashes, 20 lbs. of muriate of soda and 5 lbs. of a.r.s.enic. The composition for looking gla.s.s plates, is 60 lbs. of clean white sand, 25 lbs. of purified sub-carbonate of pota.s.s, 15 lbs. of nitrate of pota.s.s, and 7 lbs. of borate of soda.

Common green bottle gla.s.s is made from 200 lbs. of wood ashes, and 100 lbs. of sand. The materials for making gla.s.s, is first reduced to powder; then mixed and exposed to a strong heat, in suitable pots and furnaces, till the whole ma.s.s liquifies and becomes thoroughly commixed and transparent.

107. COMPOSITION OF VARIOUS ALLOYS.--Bra.s.s is composed of two parts of copper to one of zinc; or copper and calamine, (an ore of zinc,) equal quant.i.ties. Pinchbeck consists of from five to ten parts copper, and one of zinc. Bell metal is composed of three parts copper and one of tin. Gun metal, nine parts copper and one of tin. Tombac, sixteen parts copper, one part zinc and one of tin. The composition of pewter is seven pounds of tin, one of lead, four ounces of copper and two of zinc. That of type-metal is nine parts lead, two parts antimony and one of bis.m.u.th. Solder, two parts of lead with one of tin. Queen's metal, nine parts of tin, one of bis.m.u.th, one of antimony and one of lead. Jewel gold is composed of twenty-five parts gold, four parts silver, and seven parts fine copper. In forming metallic compounds or alloys, it is proper to melt such of the ingredients as are the least fusible first, and afterwards add the others, stirring them briskly till they are thoroughly commixed.

108. TO PRODUCE VARIOUS KINDS OF GAS.--To three or four ounces of pulverized chalk or marble, moistened in a flask, with an equal quant.i.ty of water, add one ounce of sulphuric acid;--carbonic acid gas will be evolved in abundance, and will rise through the neck of the flask, and may be conducted by pipes, to any proper receiver. Instead of the marble or chalk, subst.i.tute granulated zinc;--in this case hydrogen gas will be evolved; but this may require a larger proportion of water. Pour sulphuric acid upon a similar quant.i.ty of dry muriate of soda;--muriatic acid gas will be rapidly evolved. Proceed in the same manner with a similar quant.i.ty of black oxide of manganese,--apply the heat of a lamp, and oxygen gas will be produced. Put into the flask, two or three ounces of lean beef, cut into small pieces; pour over them one ounce of nitric acid diluted with three ounces of water; apply the heat of a lamp, and nitrogen gas will be liberated. Powder separately, equal quant.i.ties of muriate of ammonia and newly burnt lime; put them together into a flask and apply gentle heat; ammoniacal gas will be evolved. Pour an ounce of nitric acid, diluted with five times its weight of water, upon one ounce of shreds or turnings of copper; nitrous gas will be rapidly evolved. Grind three parts of muriate of soda with two parts of black oxide of manganese; introduce this mixture into the flask, and add two parts of sulphuric acid, diluted with an equal quant.i.ty of water; apply a gentle heat and chlorine gas will be evolved. _Note._--When either of the last mentioned gases are produced, great caution is requisite that they do not escape into the room, in any considerable quant.i.ty, as their action on the lungs is exceedingly injurious.

109. VARIOUS CHEMICAL TESTS.--When water is suspected to hold any foreign substance in solution, various means may be used to detect and ascertain the quality of the substances combined; thus, acids may be detected by immersing in the water, a slip of litmus colored paper, which, if acid be present, will be changed to red. In the same manner, alkalies may be detected by a strip of turmeric yellow paper, which will be also changed to red by alkalies. These tests are sensible to the presence of an acid or alkali in the proportion of one to ten thousand. Iron may be detected by a drop of infusion of galls, which will give to the water (if iron be present) a brown tinge. A drop of sulphuric acid, precipitates barites in the form of a white powder.

Clear transparent lime-water (water in which lime has been slaked and then suffered to settle) will indicate the presence of carbonic acid by a milky whiteness. On the same principle, a solution of super-carbonate of pota.s.s will detect lime. A few drops of nitrate of silver will instantly discover muriatic acid, by a white flaky precipitate. Muriatic acid, consequently, is a good test for silver.

Acetate of lead, in solution, is a test for sulphureted hydrogen, which occasions a precipitate of a black colour. Nitrate of mercury is an excellent test for ammonia, one part of which, with 30,000 parts of water is indicated by a blackish yellow tinge on adding the test.

Liquid ammonia is a very sensible test for copper, with which it strikes a fine blue colour. Nitro-muriate of gold will discover the presence of tin, by a beautiful purple precipitate. Nitro-muriate of tin is, on the same principle, an excellent test for gold.

110. TO PRODUCE A PICTURE INSTANTLY, IN A VARIETY OF COLOURS.--Paint any picture on paper in the usual way, only instead of colours, use the following subst.i.tutes: for green, use a solution of nitro-muriate of cobalt, for blue, a solution of sulphate of iron--for yellow, a solution of nitrate of bis.m.u.th--and for a brown, a solution of sulphate of copper. Any of these solutions may be more or less diluted, as the respective parts of the picture are to be light or dark, but none of them must be strong enough to colour the paper. This pictture is invisible: but when it is required to appear, the paper may be tacked up on the wall, and having a gla.s.s of the transparent solution of prussiate of pota.s.s (which by sight cannot be distinguished from clear water) dashed suddenly upon it, the picture will instantly appear in its full colours. A similar effect may be produced, by drawing the picture with infusion of galls, and sub-carbonate of pota.s.s; this is revived by a solution of sulphate of iron, and appears in a yellow and a brown colour.

111. A CHEAP IMITATION OF SILVER BRONZE.--Put into a crucible, an ounce of pure tin, and set it on a fire to melt; when it begins to melt, add to it an equal quant.i.ty of bis.m.u.th, and stir the mixture with an iron rod till the whole is entirely melted and incorporated.

Take the crucible then from the fire, and after the melted composition has become a little cooler, but while it is yet in a fluid state, pour into it gradually, an ounce of mercury, stirring it at the same time, that the mercury may be thoroughly conjoined with the other ingredients. When the whole is thus commixed, pour the ma.s.s out of the crucible on a stone, where, as it cools, it will take the form of an amalgam, or metallic paste; which will be easily bruised into a flaky powder, and may then be applied to sized figures in the manner of gold or silver bronze, or may be tempered with gum-water, and applied to the work with a brush or camel-hair pencil; and if properly secured with varnish or laquers will be even more durable than either silver leaf or silver bronze.

112. TO MAKE CRAYONS OF VARIOUS COLOURS.--Crayons or pastils consist of various coloured pigments or paints, formed into sticks or rolls for the purpose of drawing and shading with them in the manner of lead pencils. But that they may be of uniform texture or hardness, different ingredients and materials require some variation in the management. To make white crayons, nothing more is requisite than to mix superfine or refined whiting with alcohol, to the consistence of soft putty; form it into rolls of a convenient length and size and let them dry: or the whiting may be mixed with water and a sufficient quant.i.ty of burnt or calcined sulphate of lime to give the crayons a sufficient degree of hardness when dry. A great variety of elegant light colours may be formed by adding to the whiting prepared as above, small quant.i.ties of any of the coloured pigments. The most proper colors for crayons are lamp-black, prussian blue, burnt umber, burnt terra-de-sienna, red ochre, vermilion, lake, rose-pink, chrome yellow, yellow ochre and mineral green. Many other handsome greens are formed by mixing chrome yellow with prussian blue, varying the proportions; and purples are produced by mixing rose pink or lake with blue. Prussian blue and lake being each naturally of a binding nature, require only to be ground in water; but red ochre and vermilion should be ground in alcohol, or may have some quant.i.ty of the sulphate of lime mixed with them. Any of these colours may be mixed in any proportion with whiting or with each other, each compound having a sufficient proportion of the sulphate of lime, to give it a proper degree of hardness and strength when dry. The proper length for crayons is from two to three inches, and the size about the same as that of a tobacco-pipe stem. It is customary in making crayons, to have at hand a large piece of chalk with a plane surface, on which to lay the crayons as soon as they are rolled; the chalk absorbs a part of the moisture, which makes them dry the sooner and without cracking.

113. TO MAKE HARD SEALING WAX, OF VARIOUS COLOURS.--Take of gum-sh.e.l.lac and rosin each two ounces; and of gum-mastic one ounce; reduce them to powder and mix and melt them together over a gentle fire. Then if a red colour is required, add to the mixture one ounce of fine vermilion; for a black colour, add half an ounce of a mixture of lamp black with rum; for a blue, half an ounce of white lead with one fourth of an ounce of prussian blue; which should be previously ground together dry. To give a green colour, add finely ground verdegris; a yellow is produced by chrome yellow or gamboge; and white, by adding pure white lead to the mixture. When the desired colour is formed by the mixture and incorporation of any of the above mentioned colouring ingredients, take out a part of the mixture, sufficient to form a stick or roll of the usual size, and roll it between two smooth metallic plates, which should also be previously warmed to prevent the wax from becoming too hard. When the stick is reduced to a proper size, flatten it a little and let it cool. Proceed in the same manner with the rest of the composition; afterward hold each stick severally over a fire of charcoal, turning it quickly till the surface of the wax is completely melted, by which means the sticks will have acquired a very smooth and s.h.i.+ning polish at the surface, which they will retain when cold again. If a softer wax is required, a small quant.i.ty of bees-wax and of linseed oil may be added to the above composition, or may be subst.i.tuted in the place of the gum-mastic.

114. THE ART OF MANUFACTURING PAPER HANGINGS.--This business, which has been usually, though improperly termed paper staining, consists princ.i.p.ally in stamping or painting various figures in water colours on paper. The paper for this purpose is formed into long strips or rolls, by pasting the edges of several sheets together. The edges of the sheets should not lap on each other more than half an inch, and the usual length of a roll is about nine yards. These rolls are first painted plain with a large brush; the paint is composed of refined whiting with some colouring ingredient, being ground in water and tempered with a sufficient quant.i.ty of glue to prevent it from rubbing off; when a new design or figure is to be introduced, several colours are prepared, i.e. as many as are required in such design, and with these the design is painted on a sheet of paper. The paper is then laid on a smooth birch or maple board, and such parts of the paper as contain the colour that was last applied in the drawing (which is usually the white) are completely cut out, with a sharp pen-knife, and the parts thus cut out, are pasted down upon the board, immediately, in the places and positions they occupied in the design. The sheet is then removed to another board, and another colour is cut out in the same manner; thus the several colours are distributed in their proper arrangements on as many different boards. Each board is then cut away with chisels and gouges, to the depth of a fourth, or an eighth of an inch, in every part except where the pieces of paper are fixed. These boards or prints are supported by other thin pieces, which are fixed firmly on the backs of them by screws, in such manner that the grain of one, crosses that of the other, and thus prevents their warping.

They have also cleats or pins attached to them which serve as handles.

A trough is provided, a little larger than the prints, of one inch in depth, and having a smooth bottom, on which is laid three or four pieces of fine flannel or ca.s.simere, each of which is at least as large as the prints. Then some of the colour with which the first part of the design was painted, is spread upon the cloth with a brush; and upon this, the print containing the corresponding parts of the figure, is pressed, (the pieces of paper having been previously sc.r.a.ped off;) the print being thus charged with the colour, is placed upon one end of a roll of the prepared paper, which is laid on a table for that purpose, and is pressed down hard by a lever or screw. It is then returned to the trough, and again charged with the colour, and again impressed on the paper at a proper distance above the other impression. In this manner several rolls are printed with one colour.

Then the next colour in the design is applied to the paper in the same manner by another print;--a third colour by a third print and so on till the paper is completely printed with every colour in the design, each in its proper place. These prints should be washed and kept dry for future use. A variety of figures may be produced with the same print, by varying the colours.

115. TO MAKE ELASTIC BLACKING FOR LEATHER.--Dilute one ounce of gum-asphaltum with a pint of spirits of turpentine, in the manner described at 51;--put this into a flask, and add one ounce of gum-elastic cut into very small pieces, and half an ounce of gum-sh.e.l.lac previously reduced to powder. Suspend the flask unstopped over a fire of charcoal, or set it in a sand bath where it may boil gently till the quant.i.ty is reduced to a gill; then strain it through a flannel, and when nearly cold, bottle and cork it. The leather should be thoroughly blackened with some liquid blacking and waxed over slightly with bees-wax before the elastic blacking is applied. If the blacking should be too thick, it may again be diluted with spirits of turpentine. It should be warmed when applied, and the work may require several coats, and a considerable time for each to dry. Any of the above mentioned gums may also be dissolved in sulphuric ether, and thus produce a fine drying varnish, but the preparation is much more difficult as the volatile nature of the ether will not admit of much heat, whereby to facilitate the solution.

116. SUNDRY EXPERIMENTS.--Rub together a little dry powdered alum, and acetate of lead; both will become fluid. To a saturated solution of muriate of lime, add a saturated solution of sub-carbonate of pota.s.s, (both transparent liquids,) the mixture will be nearly solid. Rub together a little pure white calomel (sublimed mercury) and pure white ammonia (being moistened;) both will become intensely black. Fill a flask nearly half full of water, and apply heat till it boils; take it from the fire and (when it has done boiling) cork it; pour cold water upon the flask, and the water inside will re-commence boiling. Fill a gla.s.s with water, and lay a piece of paper upon the top of it; place your hand upon the paper, and invert the gla.s.s; the hand may be removed and the gla.s.s may be suspended in that position by a thread, and the water will not be spilled. Expose a piece of ice to the action of (cold) muriatic gas; the ice will be instantly melted. Drop a piece of phosphuret of lime, into a gla.s.s of water; bubbles will soon rise, and on reaching the surface of the water will spontaneously explode.

Apply the end of a roll of brimstone to a hot bar of iron; a part of the iron will be instantly melted, and will fall. Write with diluted sulphuric acid, on paper that has been coloured brown by a mixture of sulphate of iron, and infusion of galls; the writing will be white.

Moisten the under lip, and lay upon it a piece of silver money, (not less than a twenty cent piece) with the edge of it beneath the tongue; lay a piece of zinc, of nearly an equal size, upon the tongue, and bring the edges of the pieces of metal into contact; you will instantly drop the money.