398 



STEAM-GUN-STEEL. 



STEAM-GUN. As early as 1805, the French 

 general Chasseloup is said to have shown the pos- 

 sibility of preparing steam artillery. In 1814, a 

 French engineer constructed ordnance of this sort. 

 The generator supplied at once six pieces of artil- 

 lery with stoaui. The turning of a cock supplied 

 all the pieces at once with balls and steam. This 

 machine could make 150 discharges in a minute. 

 The steam artillery invented by Jacob Perkins is 

 thus described by him, in a letter to doctor Jones, 

 editor of the Franklin Journal, dated March 8, 

 1827: " I am now engaged in building steam artil- 

 lery, as well as musketry, for the French govern- 

 ment. The piece of ordnance is to throw sixty 

 balls, of four pounds each, in a minute, with the 

 correctness of the rifled musket, and to a propor- 

 tionate distance. A musket is also attached to the 

 same generator, for throwing a stream of lead from 

 the bastion of a fort, and is made so far portable as 

 to be capable of being moved from one bastion to 

 another. The musket is to throw from one hundred 

 to one thousand bullets per minute, as occasion may 

 require, and that for any given length of time. I 

 am within the truth when I say that, if the dis- 

 charges are rapid, one pound of coals will throw as 

 many balls as four pounds of powder." 



STEARINE. See Fat, and Soap. 



STEATITE (soapstone). All the varieties of 

 steatite are so soft that they may be easily cut by 

 a knife, and in most cases scratched by the nail. 

 Its powder and surface are soft, and more or less 

 unctuous to the touch. It is seldom translucent 

 except at the edges. Its fracture is, in general, 

 splintery, earthy or slaty, with little or no lustre. 

 By friction it communicates to sealing-wax negative 

 electricity. Exposed to heat, it becomes much 

 harder, but is almost infusible by the blow-pipe. 

 It is a compound of silica, magnesia, alumina, oxide 

 of iron, and water. It is sometimes much mixed 

 with talc, asbestus, &c. It is very common in 

 Cornwall and Germany. Common steatite is usu- 

 ally solid, and its texture compact : sometimes it is 

 almost friable, and its texture earthy. Its surface 

 is often like soap to the touch. Its colour is usu- 

 ally gray or white, seldom pure, but variously mixed 

 with green, yellow or red, and is sometimes a pale 

 yellow, red or green, of different shades. The 

 colours sometimes appear in spots, veins, &c. Its 

 specific gravity is usually between 2-38 and 2-66. 

 When solid, it is somewhat difficult to break. It 

 sometimes presents pseudomorphous crystals. It 

 agrees with talc in its composition. Common 

 steatite occurs in masses or veins, or small beds, in 

 primitive and transition rocks, more particularly in 

 se rpentine. The variety of steatite, called potstone 

 is in hardness nearly the same as common steatite, 

 but is more tenacious. The substance employed in 

 th e arts under the name of soapstone, usually be- 

 longs to steatite, but sometimes to lamellar or in- 

 durated talc. Steatite is not susceptible of a good 

 polish ; but its softness and tenacity, in consequence 

 of which it may be cut or turned into various forms, 

 and its property of becoming hard by heat, render 

 it a useful mineral in the arts. It is employed for 

 the hearths of furnaces, the sides of fire-places and 

 stoves, &c. The potstone has received its name 

 from having been manufactured into culinary ves- 

 sels. The common steatite has even been employed 

 for the purpose of engraving; for, being easily cut 

 when soft, it may be made to assume any desired 

 form, and afterwards rendered hard by heat. It 

 then becomes susceptible of a polish, and may be 



variously coloured by metallic solutions. Steatite 

 is used in Britain in the manufacture of porcelain. 

 It has a great affinity for glass. It is also employed 

 in the manner of paste, reduced to a fine powder, 

 and mixed with colouring matters, for painting on 

 this substance. Tailors and embroiderers prefer it 

 to chalk for marking silk. It possesses the pro- 

 perty of uniting with oils and fat bodies, and enters 

 into the composition of the greater number of the 

 balls which are employed for cleaning silks and 

 woollen cloths. It also forms the basis of some 

 preparations of paints. It is used to give lustre to 

 marble, serpentine and gypseous stones. Mixed 

 with oil, it serves to polish mirrors of metal and 

 crystal. When leather, recently prepared, is 

 sprinkled with steatite to give it colour, and after- 

 wards, when dry, is rubbed several times with a 

 piece of horn, it assumes a very beautiful polish. 

 Steatite is also used in the preparation of glazed 

 paper. It facilitates the action of screws, and from 

 its unctuosity, may be employed with much advan- 

 tage for diminishing the friction of the parts of 

 machines which are made of metal. 



STEEL is a compound of iron and carbon. The 

 furnace in which iron is converted into steel, has 

 the form of a large oven, or arch, terminating in a 

 vent at the top. The floor of this oven is flat and 

 level. Immediately under it there is a large arched 

 fire-place, with grates, which runs quite across from 

 one side to the other, so as to have two doors for 

 putting in the fuel from the outside of the building. 

 A number of vents, or flues, pass from the fire- 

 place to different parts of the floor of the oven, and 

 throw up their flame into it, so as to heat all parts 

 of it equally. In the oven itself, there are two 

 large and long cases or boxes, built of good fire 

 stone ; and in these boxes the bars of iron are re- 

 gularly stratified with charcoal powder, ten or 

 twelve tons of iron being put in at once, and the 

 box is covered on the top with a bed of sand. The 

 heat is kept up, so that the boxes and all their con- 

 tents are red hot for eight or ten days. A bar is 

 then drawn out and examined ; and if it be found 

 then sufficiently converted into steel, the fire is 

 withdrawn and the oven allowed to cool. This 

 process is called cementation. The bars of steel 

 formed in this way are raised, in many .parts, into 

 small blisters, obviously by a gas evolved in the in- 

 terior of the bar, which had pushed up, by its elas- 

 ticity, a film of the metal. On this account, the 

 steel made by this process is usually called blistered 

 steel. The bars of blistered steel are heated to 

 redness, and drawn out into smaller bars by means 

 of a hammer, driven by water or steam, and strik- 

 ing with great rapidity. This hammer is called a 

 tilting hammer, on which account, the small bars 

 formed by it are called tilted steel. When the bars are 

 broken in pieces and welded repeatedly, and then 

 drawn out into bars, they acquire the name of Ger- 

 man or shear steel. Steel of cementation, however 

 carefully made, is never quite equable in its texture ; 

 but it is rendered quite so by fusing it in a crucible, 

 and then casting it into bars. Thus treated, it is 

 called cast-steel. When steel is to be cast, it is 

 made by cementation in the usual way, only the 

 process is carried somewhat farther, so as to give 

 the steel a whiter colour. It is then broken into 

 small pieces, and put into a crucible of excellent 

 fire clay, after which the mouth of the crucible is 

 filled up with vitrefiable sand, to prevent the steel 

 from being oxidized by the action of the air. The 

 crucible is exposed for five or six hours to the most 



