CHEMICAL SCIENCE. 207 



and carbonized lime dust. This latter material will be valuable in agricul- 

 ture ; it should be worked into the land when preparing it for seed, muriate 

 of ammonia being afterward applied to the growing crop, when the first 

 shower of rain will carry it into the soil, when carbonate of ammonia will be 

 disengaged in direct contact with the root of the plant. By treating gypsum 

 as sulphate of lime, with small coal and high heat in a reverberatory furnace, 

 it would be reduced to sulphuret of calcium, and may, by a similar mode of 

 treatment, yield the same product as alkali refuse. 



REFUSE OF SMELTIXG FURXACES. 



The production of iron by the smel ting-furnaces of Great Britain has reached 

 3,000,000 tons annually; and by a moderate calculation, it may be assumed 

 that for every ton of iron two tons of slag are formed, making an aggregate of 

 at least 6,000,000 tons of this hitherto refuse material. Not only has this 

 vast accumulation of slag been to the present time comparatively useless, but 

 it has proved an incumbrance and source of heavy expense to the ironmasters ; 

 for it is calculated that a sum of not less that 150,000 sterling is annually 

 expended by and lost to them in removing the unsightly heaps from their 

 premises, to be used as the most worthless of materials in mending old roads, 

 and in filling gullies and other vacant spaces. 



Within the past year, however, a company has been formed in England for 

 the purpose of turning this heretofore waste material to a useful account, 

 under the direction of Dr. W. H. Smith, of Philadelphia, the patentee of the 

 process. In a paper read before the London Society of Arts, Dr. Smith stated 

 that according to the treatment it receives, slag can be rendered brittle or 

 tough, hard or soft, compact or porous, rough or smooth. It can be cast into 

 as great a variety of forms, solid and hollow, as iron itself, with the superior 

 advantage of being susceptible of the admixture and blending of colors, so as 

 to render it equal in brilliancy to agate, jasper, malachite, the variegated 

 marbles, and other more valuable varieties of the mineral kingdom. When 

 properly annealed, it can be made to acquire a "surface, or texture, at least 10 

 times as durable as that of marble, and is susceptible of a polish equal to 

 agate or cornelian. As a building material, slag can be readily adapted to 

 any variety of architectural design, from the simple slab to the most ornate 

 and complex decoration ; while its beauty and durability chiefly recommend 

 it as an article of luxury. 



Dr. Smith entered into a comparison of the relative expense of the manu- 

 facture of clay bricks as compared with that of bricks or blocks of slag ; and 

 he reminded us, that in making bricks of the latter, the raw material costs 

 less than nothing, inasmuch as the ironmaster saves by its utilization the 

 heavy expenditure now attendant upon its removal from the furnace premises. 

 In fusing slag for the operation of casting no expense is incurred, inasmuch as 

 this item of expenditure is charged by the metallurgist to the metallic and not 

 to the earthy products of the smelting operation ; whereas, in making bricks 

 of clay, the raw material has an intrinsic value, while the consecutive operar 

 tions of digging the clay, preparing it for use, and transporting it. added to 



