412 Progress in Science. [July, 



one time, simply for the skin and for boiling down for fat ; the blood, flesh, 

 bones, and offal simply being applied as manure. 



Many attempts have been made of late years to manufacture artificial stone, 

 some of which have been attended with more or less success, as far as regards 

 the production of large blocks, but have rarely succeeded for the purpose of 

 moulding or making medallions and mosaics, or for emery-wheels, oil-stones, 

 and articles of a similar character. In almost all cases, too, the agency of 

 heat has been required for producing articles in artificial stone, and this has 

 been found very objectionable, as well as expensive. Attention has recently 

 been called to some specimens of artificial stone in the shape of medallions, 

 mosaics, emery-stones, oil-stones, imitation marble, &c, which have been pro- 

 duced in a simple manner, by moulding without the agency of heat, and which 

 appear to partake in every respect of the nature of the stones they are intended 

 to represent. These specimens are formed from natural materials, agglo- 

 merated by means of a cement, the invention of M. Sorel, a French chemist, 

 well known in connection with the introduction into this country of the gal- 

 vanised iron process. This new cement is formed of basic oxychloride of mag- 

 nesium (oxide of magnesium and chloride of magnesium), either pure or 

 mixed with other substances. The cement may be made in two different ways, 

 viz., either by diluting or tempering magnesia, which may be more or less 

 hydrated and carbonated, with a solution of chloride of magnesium more or 

 less concentrated ; or by adding to the magnesia chloride of magnesium in a 

 dry state, and employing water to form the cement. The cement thus produced 

 is specially white and hard, and may with advantage be used in place of some 

 of the best cements. It possesses the same hardness, and will receive the 

 same polish as marble, thus enabling it to be employed in the manufacture of 

 artificial marble, mosaic pavements, and statuary. Imitation ivory can be made 

 from it for making billiard balls and other similar articles, also medallions, 

 buttons, &c. By combination with mineral colours, the cement may be made 

 to assume any desired tint, may be moulded like plaster, and be employed in 

 the manufacture or imitation of innumerable objects of art or ornament. In 

 practice, the cement is never used used in a pure form, but in combination with 

 other materials ; which, being incorporated with it while in the moist condi- 

 tion, are in the subsequent setting mechanically bound together into a solid 

 mass. For this purpose, the magnesia, in fine powder, is mixed with mineral 

 substances, such as sand, gravel, dust, or chips from marble or other stones, or 

 with emery, quartz, or other grits of various kinds, in varying proportions, ac- 

 cording to the result desired. This mixture is then moistened with a solution 

 of the chloride of magnesium, or with the bittern from salt works. In some cases 

 it is made sufficiently wet to form a mortar, and in others only to pro- 

 duce a condition of dampness like that of moulding sand. The mixture may be 

 effected in troughs, hy hand labour, the materials being worked over with 

 shovels or hoes ; or, more expeditiously, in mixing machines designed ex- 

 pressly for the purpose, and worked by horse or steam power. The materials 

 of which this cementing substance is composed are abundantly distributed 

 over the surface of the globe. Magnesia sufficiently pure for the purpose is 

 obtained by simply calcining mineral magnesite, large deposits of which are 

 known to exist in Prussia, Greece, Canada, California, Pennsylvania, and 

 Maryland. Deposits will doubtless be found in other places when the demand 

 is made for the material. The chloride of magnesium is readily obtained by 

 concentrating sea water, the bittern of salt works being sufficiently pure for 

 the purpose. Sea water concentrated at 30 B. precipitates nearly the whole 

 of its chloride of sodium. In the " Sorel " process, it is concentrated to 33 B., 

 when all the chloride of sodium is practically crystallised and precipitated, the 

 mother-liquor retaining, besides the chloride of magnesium, some chloride of 

 potassium and some sulphate of magnesia, which seem to add strength to 

 the cement, as the water in this state makes a stronger stone than the pure chlo- 

 ride of magnesium. 





