" MOLECULAR COALESCENCE," ETC. 221 



as far as the width of the phial will permit ; and, lastly, the 

 bottle is to be filled up with a solution of gum arable in com- 

 mon Avater, of 1"0844 specific gravity, one ounce of which 

 will weigh 520 grains. This solution must also be perfectly 

 clear, having been first strained through cloth, and then left 

 to stand for some days to allow of the subsidence of all the 

 floating vegetable matter. It must also be added carefully to 

 the alkaline solution, that the two solutions may be mixed as 

 little as possible in this part of the process. The bottle must 

 now be kept perfectly still, covered with a piece of paper, to 

 prevent the admission of dust for three weeks or a month. 

 Time would be saved by having a dozen bottles thus charged, 

 and examining their contents at stated intervals, according 

 to the chief object sought for in the experiment. The soluble 

 salts of lime to be decomposed by the subcarbonate of potash 

 are contained in the gum, in combination with malic acid, 

 and also in the common water ; ammoniaco-magnesian or 

 triple phosphate is also contained in the gum, and is set free 

 by the alkali. Muriate of lime, dissolved in a solution of 

 gum from which all the lime had 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 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 magnesia, evincing no 

 tendency to become globular." 



Although gum is here recommended as the most suitable 

 matrix, it must be noted that all kinds of viscid substances 

 had been used in the series of experiments, and that gum was 

 finally chosen because the most perfect globules Avere obtained 

 under its influence. 



In later experiments, not recorded in his book, but sej)a- 

 rately published, Mr. Rainey caused the mixture of the two 

 viscid solutions to be effected on microscopic slides under 

 large pieces of thin glass. By this method he was enabled 

 to watch the process of coalescence day by day. Within the 

 last month I have seen one of these slides originally prepared 

 several years ago. 



After working out with great care the building-up of 

 the globules from amorphous molecular matter, our author 



