BY MOLECULAR COALESCENCE. 57 
uncovered for three weeks, when sufficient of the fluid 
in one of them is to be put into the other entirely to fill 
it, none of the solid material being introduced with it. 
These two bottles may now stand for six weeks or two 
months, the one bottle bemg kept full by the occasional 
addition of fluid from the other. Now, at the expiration 
of the time mentioned, it will be obvious that the density 
of the fluid in the bottle which had been tied over, and 
from which, therefore, all evaporation had been prevented, 
will be much less than that which had been kept full 
by the addition of the fluid from the third bottle; and 
hence the globules on the slides in these two bottles will 
have been for some time under different mechanical cir- 
cumstances, one set of globules having been kept in con- 
tact with a fluid less dense than that m contact with the 
other globules, whilst the chemical composition of these 
two will be as much alike as can be under such cir- 
cumstances. Any difference then which may be found 
in the globules of the two slides can only be attributable 
to a mechanical cause. All the solid matter must be re- 
moved from the upper surface of these slides, and that on 
the lower, after beimg well washed, may be examined 
either in Canada balsam or in glycerine, all the slides 
being treated exactly in the same manner. It will be 
found, on comparing the specimens, that the globules on 
the slides taken from the fluid which had not been allowed 
to evaporate will be clear, with a sharp outline, and either 
laminated or not, according to the quantity of carbonate 
in their composition. Indeed, all the globules on these 
slides will answer to the description given at page 36. 
The globules on the other slides will be altered in their 
structure, the amount of difference depending upon the 
relative densities of the fluids in the different bottles, and 
