278 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
analyses of mineral waters show, the composition of the solutions 
which deposit the crystals of a given substance varies from one 
region to another as much in the quality as in the quantity of the 
different elements dissolved. But all crystals do not lend themselves 
with the same facility to these modifications of the faces; and just 
as there exist in nature bodies like calcite which possess the most 
varied habits, there exist also artificial compounds, the crystals of 
which may appear in a great number of forms depending on the 
condition of crystallization, as, for example, phthalic acid, meconic 
acid, nitrate and oxalate of urea. 
