THE SCIENCE OF CLAY- WORKING. 461 



of the methods of brick-making, but of the philosophy of those methods and 

 as to what improvement is reasonable and can be expected. 



The material used for brick and tile making is probably the most abundant 

 in nature; there is scarce a township but what affords clay, inferior though 

 it may be, that will make, when properly worked, brick or tile. 



The character of the material is no doubt the most important feature in 

 the manufacture of brick or tile, and common prudence would require that 

 it be well investigated before extensive manufacture be commenced. I have 

 often seen it stated that the only way to tell the quality of clay was by actual 

 trial of the operations of manufacture. This is no doubt true, but the admis- 

 sion of that truth indicates deplorable ignorance on our part. It is a fact 

 that we understand but little about clay. 



In 1828 VVohler discovered the existence of the metal aluminum. This 

 metal possesses properties which render it the most valuable of all metals for 

 commercial use. It is malleable, very strong, a good conductor of electricity, 

 and besides all this it is very light, being only about one-fourth as heavy as 

 iron. It will not corrode, and when once polished will retain its brightness 

 for years. This metal exists in greater abundance than any other metal. 

 Every clay bank is a mine, from which the ore of aluminum can be had in 

 abundance. Pure clay is an ore of aluminum, and consists of about one- 

 half part aluminum and about one-half part silica and other minerals. Yet 

 despite its great abundance, aluminum is still one of our precious metals, its 

 price not admitting of its common use. Every year, however, advances our 

 knowledge respecting this precious metal, and improves the art of extract- 

 ing it. This improvement has a marked effect on the price, and it is claimed 

 that it soon will be sold as low as ten or fifteen cents per pound. The most 

 successful method of reduction is by the electric furnace, by means of which 

 a heat of five or six thousand degrees can be produced. The largest dynamo 

 in the world is in use by Cowles Bros., at Lockport, N. Y., for the purpose of 

 reducing aluminum ore. At present no successful method is in use, by 

 means of which it can be reduced directly from the clay. The ores from 

 which it is extracted are the chloride and sulphide of aluminum. 



A great fortune awaits the inventor who successfully brings out a cheap 

 process of reducing aluminum from the clay. The other ingredient of pure 

 clay, silicon, exists as an oxide called silica, quite pure in certain of our 

 hardest rocks. The compound is silicate of aluminum, with properties essen- 

 tially different from either of its constituents. 



Silicate of aluminum is found nearly pure in China clay. It is, however, 

 always associated and chemically combined with a certain amount of water. 



This water cannot be removed by any ordinary process of drying. It may, 

 however, be removed by burning at a temperature of over 1000° P. It is to 

 this water that clay owes its peculiar plastic character. When this water has 

 once been removed by burning, the chemical nature of the silicate of aluminum 

 is so changed that it will never again take water as part of its chemical com- 

 position, and consequently never again become a plastic material. 



Water may make it crumble or fall in pieces, but it falls in pieces more 

 like a lump of sand than a lump of clay. It is never again sticky or plastic. 



Silicate of aluminum or pure clay in burning shrinks to a considerable 

 extent, and if the heat is not perfectly uniform on each side, ware 

 made from it will warp in burning. This fact makes it necessary to add 

 some substance which will counteract the effect of the fire to a greater or less 



