METALS. 



421 



The large air-furnace is fed with dry-wood fuel, 

 and will nielt upward of 1,000 kilometres. 



In olden times statues were always cast in a loam- 

 mould, put together piece by piece in the excavated 

 pit, and, as fitted in place andjointed up, the pit was 

 rammed up round them. This was but a make-shift 

 mode, and had several serious evils : the mould never 

 could be dried with perfect uniformity and, even 

 when dry, it stood so long in the pit while being got 

 ready, that it imbibed moisture anew, and hence so 

 many " miscasts " of old. Under the heavy head of 

 liquid bronze, too, the ramming-in of the pit some- 

 times proved soft and deceptive, so that here or there 

 the walls of the mould partially bulged, and the 

 casting was either lost or damaged. 



All M. Barbedienne's statues or large objects are 

 east therefore in cast-iron flasks or boxes, so that the 

 pit is what iron-founders call a " naked pit," i. e., no 

 rammmg-up is practised. 



A " pool, or reservoir of sand, with charcoal facing, 

 is employed for all large castings, into which the 

 contents of the crucibles are " teemed," or into which 

 the air-furnace is tapped. When the full quantity of 

 metal is in the pool, an iron conical plug, which had 

 been inserted into and stopped the mam "gait," or 

 " coulee^ is drawn up, and the metal enters the 

 mould. 



It passes oif (as overplus) by " rising heads," as in 

 cast-iron moulding ? and "the gas is fired" at these 

 by a lighted torch in the same way. From the low 

 temperature of the liquid bronze, however, as com- 

 pared with cast iron, but a small volume of gas is 

 evolved from either moulds or cores. 



The head of surplus pressure employed is always 

 very small, for fear of distortion ; a practice exactly 

 the reverse of that of bronze-gun founding, where 

 the "masselet," or " rising head," is often nearly as 

 long as the gun itself above its muzzle, which is 

 uppermost in the mould. It may be very much 

 doubted, or even on plausible grounds contested, 

 whether any advantage is obtained by those very 

 long " gun-heads," and whether some positive evils 

 in the increased segregation of the alloy be not thus 

 introduced. Bronze-gun founding, however, is now, 

 in these days of huge wrought-iron artillery, some- 

 what an art of the past, it may be said. We must 

 remember, however, that Prussia is returning to 

 bronze rifled field-guns, and that our new rifled Indian 

 artillery is also to be of bronze. 



The metals employed by M. Barbedienne for his 

 bronze are very pure " tile-pitch " copper, and English 

 or Straits tin, also of best quality. The copper is 

 usually South American, again melted in France, 

 purified by " liquation," and run into small pigs of 

 about the size and form of ours known as "'best 

 selected copper." 



< Whitworth Metal. Mr. Whitworth, the dis- 

 tinguished inventor of the ordnance bearing 

 his name, has long been engaged in testing a 

 new process of making and casting iron and 

 steel, with a view of preventing the occurrence 

 of air-bubbles in the castings, which are the 

 frequent cause of the explosion of cannon. 

 These hubbies are formed in the molten steel 

 before it is set, and are retained in the metal, 

 no matter how severe a hammering it receives. 

 Of two pieces, manufactured at the same place, 

 about the same time, and by the same work- 

 men, one may stand a thousand rounds, and the 

 other burst destructively at the first or fiftieth 

 round the difference in the strength of the 

 pieces arising, for the most part, from the 

 presence or absence of air-bubbles. The de- 

 tails of Mr. Whitworth's process are not pub- 

 lished, but it is said to consist in . the applica- 

 tion of immense pressure to the molten metal 



while cooling. He has four qualities of this 

 steel, or Whitworth metal, as he calls it. They 

 are known as yellow (having most carbon), 

 blue, brown, and red, the red being the most 

 ductile. Having tried many experiments, on a 

 small scale, he feels justified in declaring that 

 he will now be able to make heavy guns 

 perfectly trustworthy, at a price of about 120 

 a ton. He is making preparations for the con- 

 struction, on this plan, of guns weighing as 

 high as 43 tons and over. 



Casting Steel under Pressure, Tjy Use of 

 Gunpowder. Cast steel run into moulds is 

 subject to blister, and is otherwise porous, 

 which defect reduces considerably its tough- 

 ness. In order to give the metal its requisite 

 tenacity it is subsequently reheated, and then 

 rolled and hammered. A writer in Van Nos- 

 trancPs Magazine says that, as many articles, 

 such as cannon, cannot be treated in that 

 manner, he has devised a plan of submitting 

 them to a higher pressure while in a liquid 

 state, enclosed in their moulds maintained in 

 iron flasks. For this purpose, immediately 

 after running a cannon, he covers hermetically 

 the lead by a metallic cap, by means of holts 

 or other devices attached to the flask ; this cap 

 is fitted in its centre with a vertical pipe, and 

 provided with a cock at its lower extremities, 

 while its upper extremity is closed by a 

 washer, pressed by a bolt in such a manner as 

 to act as a safety-valve. Before attaching the 

 cap at, say, one inch from the surface of the 

 liquid metal, he introduces in the vertical pipe, 

 and between the cock and the washer, about 

 one-quarter of an ounce of powder, prepared 

 in the proportions of 80 parts of saltpetre and 

 20 parts of charcoal. On opening the cock, this 

 powder falls on the metal, ignites and engenders 

 about one-third of a cubic foot of gas, at 3000 

 F. These gases exert on the liquid metal a 

 pressure which is transmitted throughout- the 

 entire mass, thereby condensing the same and 

 expelling the blisters. The effect thus pro- 

 duced is equivalent to the pressure of a head 

 of liquid metal 90 ft. high, admitting that the 

 capacity between the cap and the surface of 

 the metal contains 30 cubic inches. By mak- 

 ing the flasks sufficiently strong these charges 

 of powder may be varied so as to produce, by 

 its ignition, a uniform and general pressure, 

 which is preferable to the partial, irregular, 

 and momentary action of a hammer. 



The Ellertiausen Process. The general re- 

 sults of the Ellerhausen process, which consists 

 in the mixing of from 30 to 33 per cent, of fine 

 ore with pig-iron, previous to its treatment in 

 the puddling-furnaces, are stated by Van Nos- 

 trancPs Magazine to be a large loss of ore as 

 compared with puddling, but an improvement 

 of the iron, especially of a cold, short iron 

 made from hematite, when treated with mag- 

 netic ores. An important experiment was re- 

 cently made at the works of Henry Burden & 

 Sons, Troy. The pig-iron was melted in a pud- 

 clling-furnace, fettled with about half the usual 



