_Another curious Experiment with Oil and Water._

Drop a small quant.i.ty of oil into water agitated by the wind; it will immediately spread itself with surprising swiftness upon the surface, and the oil, though scarcely more than a tea-spoonful, will produce an instant calm over a s.p.a.ce several yards square. It should be done on the windward side of the pond or river, and you will observe it extend to the size of nearly half an acre, making it appear as smooth as a looking-gla.s.s. One remarkable circ.u.mstance in this experiment is the sudden, wide, and forcible spreading of a drop of oil on the surface of the water; for if a drop of oil be put upon a highly polished marble table, or a looking-gla.s.s, laid horizontally, the drop remains in its place, spreading very little, but when dropped on water it spreads instantly many feet round, becoming so thin as to produce the prismatic colours for a considerable s.p.a.ce, and beyond them so much thinner as to be invisible, except in its effect in smoothing the waves at a much greater distance. It seems as if a repulsion of its particles took place as soon as it touched the water, and so strong as to act on other bodies swimming on the surface, as straw, leaves, chips, &c., forcing them to recede every way from the drop, as from a centre, leaving a large clear s.p.a.ce.

_Remarkable Effects on the visual Nerves, by looking through differently-coloured Gla.s.ses._

After looking through green spectacles, the white paper of a book will, on first taking them off, appear to have a blush of red; and after looking through red gla.s.ses, a greenish cast. This seems to intimate a relation between green and red, not yet explained.

_Weather Table._

--------------------+---------------------+------------------------ NEW AND FULL MOON.

SUMMER.

WINTER.

--------------------+---------------------+------------------------ If the new or full

moon enters into

the first or last

quarter of the

hour of 12 at noon

Very rainy

Snow and rain.

If between the

hours of

(P.M.) 2 and 4

Changeable

Fair and mild.

4 and 6

Fair

Fair.

6 and 8

{ Fair, if wind

{ Fair and frosty, if

{ at N.W.

{ wind at N. or N.E.

{ Rainy, if wind

{ Rain or snow, if S.

{ at S. or S.W.

{ or S.W.

8 and 10

Ditto

Ditto.

10

Fair

Fair and frosty.

(A.M.) 2

Ditto

{ Hard frost, unless

{ wind S.S.W.

2 and 4

Cold, with frequent

showers

4 and 6

Rain

Ditto, ditto.

6 and 8

Wind and Rain

Stormy weather.

8 and 10

Changeable

{ Cold and rain, if

{ wind N.; snow if E.

10 and 12

Frequent showers

Cold, with high wind.

A COMPLETE

SYSTEM OF PYROTECHNY;

OR THE

ART OF MAKING FIRE-WORKS.

In the art of making fire-works, great attention must be paid to the well-mixing of the materials--without which all labour is thrown away; to the purity of the articles; and to the proper quant.i.ties of each.

Sulphur, to be good, must be of a high colour, and crack and bounce when held in the hand. For small fire-works, such as may be bought in the flour will be found quite good enough, but for the larger kinds, the lump brimstone ground is preferable.

_Benzoin_ is used in fire-works, more for its pleasant scent than any material use for the purposes of fire. It may be procured at the chemists, ready for use. The oil is also used in wet composition, for stars, &c.

_Of Sulphur, or Brimstone._

Sulphur is by nature the food of fire, and one of the princ.i.p.al ingredients in gunpowder, and in almost all compositions of fire-works; therefore, great care ought to be taken of its being good, and brought to the highest perfection. Now, to know when the sulphur is good, you are to observe that it be of a high yellow; and if, when held in one's hand, it crackles and bounces, it is a sign that it is fresh and good: but as the method of reducing brimstone to a powder is very troublesome, it is better to buy the flour ready made, which is done in large quant.i.ties, and in great perfection; but when a great quant.i.ty of fire-works is to be made, it is best to use the lump brimstone ground, in the same manner as gunpowder.

_Of Saltpetre._

Saltpetre being the princ.i.p.al ingredient in fire-works, and a volatile body by reason of its aqueous and aerial parts, is easily rarefied by fire; but not so soon when foul and gross, as when purified from its gross and earthy parts, which greatly r.e.t.a.r.d its velocity; therefore, when any quant.i.ty of fire-works is intended to be made, it would be necessary first to examine the saltpetre; for if it be not well cleansed from all impurities, and of a good sort, your works will not have their proper effect.

_To pulverize Saltpetre._

Take a copper kettle, the bottom being spherical, and put into it fourteen pounds of refined saltpetre, with two quarts or five pints of clean water; then put the kettle on a slow fire, and when the saltpetre is dissolved, if any impurities arise, skim them off, and keep constantly stirring it with two large spatulas, till all the water exhales; and when done enough, it will appear like white sand, and as fine as flour; but if it should boil too fast, take the kettle off the fire, and set it on some wet sand, which will prevent the nitre from sticking to the kettle. When you have pulverized a quant.i.ty of saltpetre, be careful to keep it in a dry place.

_To prepare Charcoal for Fire-works._

Charcoal is a preservative, by which the saltpetre and brimstone are made into gunpowder, by preventing the sulphur from suffocating the strong and windy exhalation of the nitre. There are several sorts of wood made use of for this purpose; some prefer hazel, others willow, and others alder. The method of burning the wood is this: cut it in pieces of two or three feet long, then slit each piece in four parts; scale off the bark and hard knots, and dry them in the sun, or in an oven; then make in the earth a square hole, and line it with bricks, in which lay the wood crossing one another, and set it on fire; when thoroughly lighted, and in a flame, cover the whole with boards, and fling earth over them close, to prevent the air from getting in, yet so as not to fall among the charcoal; and when it has lain thus for twenty-four hours, take out the coals and lay them in a dry place for use. It is to be observed, that charcoal for fire-works must always be soft and well burnt, which may be bought ready done.

_Of Gunpowder, &c._

Gunpowder being a princ.i.p.al ingredient in fire-works, it will not be improper to give a short definition of its strange explosive force, and cause of action, which, according to Dr. Shaw's opinion of the chemical cause of the explosive force of gunpowder, is as follows:--"Each grain of gunpowder consisting of a certain proportion of sulphur, nitre, and coal, the coal presently taking fire, upon contact of the smallest spark; at which time both the sulphur and the nitre immediately melt, and by means of the coal interposed between them, burst into flame; which spreading from grain to grain, propagates the same effect almost instantaneously, whence the whole ma.s.s of powder comes to be fired; and as nitre contains a large proportion both of air and water, which are now violently rarefied by the heat, a kind of fiery explosive blast is thus produced, wherein the nitre seems, by its aqueous and aerial parts, to act as bellows to the other inflammable bodies (sulphur and coal) to blow them into a flame, and carry off their whole substance in smoke and vapour."

_How to meal Gunpowder, Brimstone, and Charcoal._

There have been many methods used to grind these ingredients to a powder for fire-works, such as large mortars and pestles made of ebony, and other hard woods; but none of these methods have proved so effectual and speedy as the last invention, that of the mealing table.

This table is made of elm, with a rim round its edge four or five inches high; and at the narrow end is a slider which runs in a groove and forms part of the rim; so that when you have taken out of the table as much powder as you conveniently can, with a copper shovel, you may sweep all clean out at the slider. When you are going to meal a quant.i.ty of powder, observe not to put too much on the table at once; but when you have put in a good proportion, take a muller and rub it therewith till all the grains are broken; sift it in a lawn sieve, that has a receiver and top to it; and that which does not pa.s.s through the sieve, return again to the table and grind it more, till you have brought it all fine enough to go through the sieve. Brimstone and charcoal are ground in the same manner as gunpowder, only the muller must be made of ebony, for these ingredients being harder than powder, would stick in the grain of the elm and be very difficult to grind; and as the brimstone is apt to stick and clog to the table, it would be best to keep one for that purpose only, by which means you will always have your brimstone clean and well ground.

_Spur Fire._

This fire is the most beautiful of any composition yet known. As it requires great trouble to bring it to perfection, particular care must be paid to the following instructions. They are made generally in cases about six inches long, but not driven very hard.

CHARGE. lb. oz. CHARGE. lb. oz.

Saltpetre 4 0 } { Saltpetre 1 0 Sulphur 2 0 } or { Sulphur 0 8 Lamp-black 1 8 } { Lamp-black 4 quarts.

This composition is very difficult to mix. The saltpetre and brimstone must be first sifted together, and then put into a marble mortar, and the lamp-black with them, which you work down by degrees with a wooden pestle, till all the ingredients appear of one colour, which will be something greyish, but very near black; then drive a little into a case for trial, and fire it in a dark place; and if the sparks, which are called stars or pinks, come out in cl.u.s.ters, and afterwards spread well without any other sparks, it is a sign of its being good, otherwise, not; for if any drossy sparks appear, and the stars not full, it is then not mixed enough; but if the pinks are very small, and soon break, it is a sign that you have rubbed it too much.

This mixture, when rubbed too much, will be too fierce, and hardly show any stars; and, on the contrary, when not mixed enough, will be too weak, and throw out an obscure smoke, and lumps of dross, without any stars. The reason of this charge being called the spur fire is, because the sparks it yields have a great resemblance to the rowel of a spur, from whence it takes its name. As the beauty of this composition cannot be seen at so great a distance as brilliant fire, it has a better effect in a room than in the open air, and may be fired in a chamber without any danger; it is of so innocent a nature, that, although an improper phrase, it may be called a cold fire; and so extraordinary is the fire produced from this composition, that, if well made, the sparks will not burn a handkerchief when held in the midst of them; you may hold them in your hand while burning, with as much safety as a candle; and if you put your hand within a foot of the case, you will feel the sparks fall like drops of rain.

_To make Touch Paper._

Dissolve in some spirits of wine or vinegar, a little saltpetre; then take some purple or blue paper, wet it with the above liquor, and when dry it will be fit for use. When you paste this paper on any of your works, take care that the paste does not touch that part which is to burn.

The method of using this paper is, by cutting it into slips, long enough to go once round the mouth of the serpent, cracker, &c. When you paste on these slips, leave a little, above the mouth of the case, not pasted; then prime the case with meal-powder (see p. 165) and twist the paper to a point.

_Of such Ingredients as show themselves in Sparks, when rammed into choked Cases._

The set colours of fire produced by sparks are divided into four sorts, viz., the black, white, grey, and red; the black charges are composed of two ingredients, which are meal-powder and charcoal; the white of three, viz., saltpetre, sulphur, and charcoal; the grey of four, viz., meal-powder, saltpetre, brimstone, and charcoal; and the red of three, viz., meal-powder, charcoal, and saw-dust.