Note on the Crystallization of Carbonate of Lime. By JOHN 
Davy, M.D., F.R.S. Lond. and Edin. Communicated by 
the Author. 
When the lime in lime-water is rapidly precipitated by 
passing into it carbonic acid gas, as by blowing on it with 
air from the lungs, the precipitate examined with the micro- 
scope, is found to consist of exceedingly minute particles, 
too minute, indeed, to allow of their form being distinguished, 
being about 55570 inch in diameter, either dispersed or col- 
lected in groups. 
When precipitated in part in this way, if the jar of lime- 
water be covered with a plate of glass, so as to admit the 
access of air slowly, the crust formed after two or three 
hours’ rest, similarly examined, will be found to consist 
of granular globules, or of little masses approaching the 
globular form, about ;,5>5 of an inch in diameter, in which 
the granules or minute particles exhibit an arrangement 
somewhat symmetrical. 
If the jar still containing lime in solution, be again covered 
with glass, and allowed to remain tranquil from twelve to 
twenty-four hours, the pellicle of carbonate of lime formed 
at the end of this time, will be found in some points to differ 
from the preceding ; the globules will be found mixed with dis- 
tinct cubical crystals, varying in size from about zs355 Of an 
inch to 7,55 and ;,4,; the intermediate size the most com- 
mon. The smallest, it may be remarked, require a nice ad- 
justment to be seen distinctly. 
Lastly, if the jar be covered with a plate of glass in the 
first instance, so as to permit very slowly the entrance of air, 
the pellicle of carbonate of lime formed, will consist entirely 
of crystals, and these chiefly cubical, connected together, and 
varying in size from about zo'55 to zo55 Of an inch in dia- 
meter. 
By adding to the lime-water different substances, the form 
of the carbonate of lime in the pellicle resulting from the ab- 
sorption of carbonic acid from the atmosphere, is found to be 
altered, and that variously. I may mention a few instances 
of the effect of substances added, which have no power of 
