608 THE MICROSCOPE. 



been previously separated, would answer a similar purpose, 

 provided the muriate were not in too great excess for the 

 gum, in which case crystals of carbonate would be formed 

 together with the globules, and the surface of the slide 

 would become covered with coalescing patches of the 

 latter. Also muriate of barytes and muriate of strontia 

 when treated in the same manner as the muriate of lime, 

 furnish each a globular carbonate, the spherical form of 

 the latter being particularly perfect and beautiful. But 

 muriate of magnesia, when decomposed in the same 

 manner, and under precisely the same conditions, does 

 not furnish globules, but crystals of carbonate of mag- 

 nesia, evincing no tendency to become globular. 



" If the density of the alkaline solution exceed much 

 the degree mentioned, and if that of the simple solution 

 of gum is not equal to the degree there specified, the 

 alkali diffusing itself through the simple solution of gum 

 more rapidly than the gum contained in the lower solu- 

 tion, a larger quantity of carbonate will be found than 

 there will be gum to combine with it in the proportion 

 necessary to form the globular carbonate, and, conse- 

 quently, the carbonate of lime found in the upper part of 

 the bottle will be deficient in gum, and therefore it will 

 be crystalline and not globular. An excess of carbonate 

 of potash is also ordered to be put into the denser solu- 

 tion, so that, after one portion of alkali has precipi- 

 tated the carbonate, the other may set free the triple 

 phosphate, and these combining form the largest kinds 

 of artificial calculi." l 



Mr. Rainey shows the analogy or identity of his arti- 

 ficially formed crystals with those found in natural pro- 

 ducts both in animals and vegetables, chiefly confining 

 himself to the structure and formation of shells and bone, 

 pigmental and other cells, and the structure and develop- 

 ment of the crystalline lenses, which, he contends, are 

 all formed upon precisely the same physical principles as 

 the artificial crystals. Take, for instance, the calculi 

 found in the body : these cannot be distinguished from the 

 crystals of artificially formed carbonate of lime. Again, 



(1) G. Rainey, " On the Mode of Formation of Shells, Bone, fyc., by a process of 

 Molecular Coalescence." 1858. 



