Let the neck of a phial be ever so strait, an egg will go into it without breaking, if it be first steeped in very strong vinegar, for in process of time the vinegar does so soften it, that the sh.e.l.l will bend and extend lengthways without breaking: and when it is in, cold water thrown upon it will recover its primitive hardness, and, as Cardan says, its primitive figure.

_Light produced by Friction, even under Water._

Rub two pieces of fine lump sugar together in the dark; the effect is produced, but in a much greater degree, by two pieces of silex, or quartz: but that which affords the strongest light of any thing, is a white quartz[25] from the Land's End, considerable quant.i.ties of which are brought to Bristol, and enter into the composition of china ware. By means of two pieces of such quartz, pretty forcibly rubbed together, you may distinguish the time of the night by a watch: but, what is more surprising, the same effect is produced equally strong by rubbing the pieces of quartz together under water.

_Rosin Bubbles._

The following account of a simple and curious experiment is extracted from a letter written by Mr. Morey, of Oxford, New Hampshire, to Dr. Silliman, the editor of the American Journal of Science and Arts.

"If the end of a copper tube, or of a tobacco-pipe stem, be dipped in melted rosin, at a temperature a little above that of boiling water, taken out and held nearly in a vertical position, and blown through, bubbles will be formed of all possible sizes, from that of a hen's egg down to sizes which can hardly be discerned by the naked eye; and from their silvery l.u.s.tre, and reflection of the different rays of light, they have a pleasing appearance. Some that have been formed these eight months, are as perfect as when first made. They generally a.s.sume the form of a string of beads, many of them perfectly regular, and connected by a very fine fibre; but the production is never twice alike. If expanded by hydrogen gas, they would probably occupy the upper part of the room.

"The formation of these bubbles is ascribed to a common cause, viz. the distention of a viscous fluid by one that is aeriform; and their permanency, to the sudden congelation of the rosin thus imprisoning the air by a thin film of solid matter, and preventing its escape."

_A curious Hydraulic Experiment, called the Magical Bottle._

Take a small bottle, (see Plate) AB, Fig. 9, the neck of which must be very narrow, and provide a gla.s.s vessel, CD, the height of which exceeds that of the bottle about two inches; fill the bottle, by means of a small funnel, with red wine, and place it in the vessel CD, which is to be previously filled with water. Then, if the bottle be uncorked, the wine will presently come out of it, and rise in form of a small column, to the surface of the water; and at the same time the water entering the bottle, will supply the place of wine; for water being specifically heavier than wine, it will consequently subside to the lowest place, while the other naturally rises to the top.

A similar effect will be produced, if the bottle be filled with water, and the vessel with wine, for the bottle being placed in the vessel, in an inverted position, the water will descend to the bottom of the vessel, and the wine will rise in the bottle. The same effect may also be produced by any other liquors, the specific gravities of which are considerably different.

_Another Hydraulic Experiment, called the Miraculous Vessel._

Take a tin vessel of about six inches in height, and three in diameter, having a mouth of only a quarter of an inch wide, and in the bottom of the vessel make a number of small holes, of a size sufficient to admit a common sewing needle.

Plunge the vessel into water, with its mouth open, and when it is full, cork it, and take it out again; then, as long as the vessel remains corked, no water will come out of it; but as soon as it is uncorked, the water will immediately issue from the small holes at the bottom. It must be observed, however, that if the holes at the bottom of the vessel be more than one-sixth of an inch in diameter, or if they be too numerous, the experiment will not succeed; for, in this case, the pressure of the air against the bottom of the vessel will not be sufficient to confine the water.

_A curious Hydraulic Experiment, called Tantalus's Cup._

Take a gla.s.s, or any other vessel, (see Plate) ABCD, fig. 10. which has a small bent pipe, EFG, open at each end, running through the middle of it; then, if water or wine be poured into the gla.s.s, it will continue in it till the tube is full up to the bend F, which should be a little lower than the upper edge of the gla.s.s; but if, after this, you continue to pour more liquor into it, it will endeavour, as usual, to rise higher in the gla.s.s, but not finding room for a farther ascent in the tube, it will descend through the part EG, and run out at the end G, as long as you continue to put it in. To those who are unacquainted with the nature of the syphon, the effect may perhaps appear something more extraordinary, if the longest branch of the tube be concealed in the handle of the cup.

This is called the cup of Tantalus, from its resemblance to an experiment of the same kind, by placing an upright image in the cup, and disposing the syphon in such a manner, that, as soon as the water rises to the chin of the image, it will begin to run out through the longest leg, in the same manner as from the cup above-mentioned.

_A curious Chemical Experiment, called the Tree of Diana._

Make an amalgam, without heat, of two drachms of leaf silver with one drachm of quicksilver. Dissolve this amalgam two ounces, or a sufficient quant.i.ty, of pure nitrous acid of a moderate strength: dilute the solution in about a pound and a half of distilled water, agitate the mixture, and preserve it for use in a gla.s.s bottle with a ground stopper. When you would make your tree, put into a phial the quant.i.ty of an ounce of the above preparation, and add to it about the size of a pea of amalgam of gold or silver, as soft as b.u.t.ter: the vessel must then be left at rest, and soon afterwards small filaments will appear to issue out of the ball of amalgam, which quickly increase, and shoot out branches in the form of shrubs.

A metallic arborisation, somewhat similar, may be produced in the following manner:--Dissolve a little sugar of lead in water, and fill a phial with the solution. Pa.s.s a wire through the cork, and affix to the upper part of the wire a small bit of silver, or zinc, in such a manner that it may be immersed in the solution not far from its surface. Set the phial in some place where it may remain undisturbed, and in about twenty-four hours you will perceive the lead beginning to shoot round the wire: this process will continue going on slowly, till you have a beautiful metallic tree. If you have a wide-mouthed phial, or gla.s.s jar, the experiment may be pleasingly diversified, by arranging the wire in various forms.

_A remarkable Experiment, called Prince Rupert's Drops._

Take up a small quant.i.ty of the melted matter of gla.s.s with a tube, and let a drop of it fall into a vessel of water. This drop will have a small tail, which, being broken, the whole substance of the drop will burst, with great violence, into a fine powder, and give a little pain to the hand, but do no hurt to it.

It is a remarkable circ.u.mstance in this experiment, that the bulb, or body, will bear the stroke of a hammer, without breaking; but when the tail is broken, the above-mentioned effect is produced. If the drop be cooled in the air, the same effect will not take place; and if it be ground away on a stone, nothing extraordinary appears; but if it be put into the receiver of an air-pump, and then broken, the effect will be so violent as to produce light.

_How to make Sympathetic Inks of various Kinds._

By sympathetic inks, are meant those kinds of liquors, with which if any characters be written, they will remain invisible, till some method is used to give them a colour.

The first cla.s.s of these inks consists of such as become visible by pa.s.sing another liquor over them, or by exposing them to the vapour of that liquor.

The second, of those which do not appear so long as they are kept close, but soon become visible on being exposed to the air.

The third, of such as become apparent by strewing or sifting some very fine powder over them.

The fourth, of those which do not become visible till they are exposed to the fire, or heated.

The fifth, like the fourth, of such as appear by heat, but disappear again when the paper becomes cold, or has had a sufficient time to imbibe the moisture of the air.

_Sympathetic Inks of the First Cla.s.s._--Put some litharge into strong distilled vinegar, and let it stand for twenty-four hours; then strain it off, and, after it is quite settled, put it into a bottle closely corked, and preserve it for use. Having done this, put into a pint bottle two ounces of quicklime, one ounce of orpiment in powder, and as much water as will rise two or three fingers' breadth above them; and when the solution is made, pour the liquid gently off, and let it stand in the sun for two or three days, observing to turn it five or six times each day.

When these liquors are ready for use, any letters written by the first, being exposed to the vapours of the second, will quickly become visible; and if you would have them disappear again, you must draw a sponge, or pencil, dipt in aqua-fortis, or spirit of nitre, over them: and if, after this, you would have them appear again, stay till the paper is quite dry, and then pa.s.s the vivifying liquor, made of the solution of orpiment, over them, as before.

_Another Ink of this Cla.s.s._--Dissolve bis.m.u.th in the nitrous acid, and any letters written with this ink will become quite black, by being exposed to the vapour of liver of sulphur, which is of so penetrating a nature, that it will act upon the ink through a quire of paper, or even the slight part.i.tion of a room.

_A Sympathetic Gold Ink of the Second Cla.s.s._--Put as much gold into a small quant.i.ty of aqua-regia as will dissolve it, and then dilute it with two or three times as much distilled water.

Also dissolve, in a separate vessel, fine pewter in aqua-regia; and when it is well saturated, add to it an equal quant.i.ty of distilled water.

Then, if any characters be written with the solution of gold, put them in the shade till they become quite dry, and they will not appear for the first seven or eight hours, but if you dip a pencil, or small fine sponge, in the solution of pewter, and draw it lightly over the invisible characters, they will presently appear of a purple colour.

The purple colour of these letters may be effaced again, by wetting them with aqua-regia, and may be produced a second time, by pa.s.sing the solution of pewter over them as before.

_A Sympathetic Ink of the Second Cla.s.s._--Dissolve fine silver in aqua-fortis, and add some distilled water to the solution, in the same manner as in the gold ink; then, whatever is written with this ink, will remain invisible for three or four months, if it be kept close from the air; but if it be exposed to the sun, it will appear in about an hour, of a gray colour, like that of a slate.

_Sympathetic Inks of the Third Cla.s.s_,--or such as become visible by having any fine powder strewed over them,--may be composed of the glutinous and colourless juice of any vegetable, the milk of animals, and several other substances.

_Sympathetic Inks of the Fourth Cla.s.s_,--are made by diluting acid of vitriol with about three times its weight of common water, or as much as will prevent it from corroding the paper. The juice of lemons, or onions, will answer the same purpose; but either of them requires more heat than the first, and will not keep so long.

_A Green Ink of the Fifth Cla.s.s._--Take zaffre in powder, and let it remain dissolved in aqua-regia for twenty-four hours; after which pour the liquor off clear, and, adding to it as much common water, keep it in a bottle well corked. Then, if any characters be written with this ink, and exposed to the fire, or strong rays of the sun, they will appear of a lively green.

It is the peculiar property of this ink, that as soon as the paper becomes cold again, the letters will disappear; and this alternate appearance and disappearance may be repeated a great number of times, provided the heat be not too great.

_Other Sympathetic Inks._

A _Yellow Ink_ of this kind may be made, by steeping the flowers of marigolds seven or eight days in clear distilled vinegar, and then pressing them out, and keeping the liquor well corked in a bottle for use.

_For a Red invisible Ink_,--take the pure spirit of vitriol, or that of nitre, and add to it eight or ten times as much water, according as you would have it more or less red.

_For a Green Ink of this sort_,--dissolve salt of tartar, the clearest and driest you can procure, in a sufficient quant.i.ty of river water; _and for a Violet sympathetic Ink_, express the juice of lemons, and keep it in a bottle well corked.

Then, if any characters be written with one of these inks, they will appear in their proper colours, the paper having been dipped in the following liquor.