24 RAIXEYj OX CAllRONATE OP LIMK GLOllULES. 



and afterwards increase in size, will depend npon the densi- 

 ties of the solutions. If they arc not very dense, globular 

 particles will be apparent in a few hours; but if they are as 

 thick as they can be, to admit of being attracted into the 

 cell, the carbonate Mill remain in an amorphous state for a 

 week or two. The best results are produced when the solu- 

 tions are as thick as possible. In this case the globules will 

 go on gradually increasing in diameter for four or five months, 

 and I have no doubt but the experiment might be so per- 

 formed that this period would be greatly prolonged, as it will 

 depend upon the relative proportions of the simple and alka- 

 line solutions of gum, so that the globules would keep gro^Ting 

 so long as there is any simple solution to furnish the earthy 

 carbonate, and alkaline solution to decompose the salts of 

 lime it contains. At first, the globules increase rapidly, but 

 afterwai'ds slowly, and ultimately they acquire even a larger 

 size than those formed according to the first process. The 

 great advantage of this mode of experimenting is that, by 

 the employment of the micrometer, the progressive changes 

 taking place in the form and shape of the globules can be 

 accurately measured. And, besides, such experiments require 

 but little time, and mav be said to be attended with no ex- 

 pense. The mechanical conditions, also, under which these 

 globules are produced resemble more those in shell-tissues. 

 I may add, that the solutions ought to be made perfectly 

 clear by repeatedly filtering ; if not sufficiently thick, they 

 must be further inspissated. On a careful examination of the 

 contents of these cells as above prepared, the first appearance 

 is that of a cloudiness of the fluid in the cell where the solu- 

 tions are in the act of mixing, Avhich, if the solutions are 

 very dense, remain so for several days, after M'hich it becomes 

 slightly granular ; if, on the contrary, a thin solution of gum 

 is employed, minute globules and dumb-bells appear in a few 

 hours. The same amorphous condition of the carbonate wdth 

 gum is obtained by mixing intimately sti'ong alkaline and 

 simple solutions of gum together, and filtering the mixture 

 through blotting-paper. After four times filtering, I 

 have found amorphous matter in the filtered fluid, which 

 afterwards passes into globules and dumb-bells ; but globules 

 formed in this manner do not increase much, but remain 

 small, and nearly all about the same size. 



The globules which form on the part of the floor of the cell 

 covered with amorphous deposit have in their centre a quan- 

 tity, more or less abundant, of granular, amorphous matter, 

 sometimes surrounded by a granular layer or two (see 

 Plate IV, fig. 1). As these globules increase, the amorphous 



