BY MOLECULAR COALESCENCE. 5 
nature of polarized light, and to a more accurate know- 
ledge of the cause of crystallization. Upon the former of 
these topics I shall not be able to touch in this paper, but 
I shall offer some observations upon the latter. This 
globular form of carbonate of lime was first observed by 
me in 1849, and was shown at that time to several of 
my friends ; but I did not discover its general properties, 
and its existence in organic products, until the year 1856. 
I may observe, however, that in the interval between 
these dates I had carefully examined a variety of morbid 
products, especially a form of corpuscle called by patholo- 
gists “ glomerulus,” whose globular form I felt convinced 
was due to a mechanical cause; and that from this con- 
viction I was led to the further examination of the bodies 
I had discovered in 1849. 
After numberless experiments made with a view to 
determine the process best adapted for furnishing these 
calculi of the largest size, and in the shortest space of 
time, I found the following to answer best, which, if 
strictly followed, will never fail to ensure satisfactory 
results. This process is given in the ‘Transactions of the 
Microscopical Society,’ published in the ‘Quarterly Journal 
of Microscopical Science’ for January, 1858. It consists 
in introducing into a two-ounce phial, about three mches 
in height, with a mouth about one inch and a quarter in 
width, half an ounce by measure of a solution of gum 
arabic saturated with carbonate of potash (the sub-car- 
bonate of the old pharmacopeeias). The specific gravity 
of the compound solution should be 1°4068, when one 
ounce will weigh 672 grams. This solution must be 
perfectly clear; all the carbonate of lime which had been 
formed by the decomposition of the malate of lime con- 
tained in the gum, and also all the triple phosphate set 
