THE FORMATION, GROWTH, AND HABIT OF CRYSTALS. 
By Paut GAvuBERT, D. Sc., 
Assistant in Mineralogy at the Natural History Museum, Paris. 
A crystal arouses the interest of the observer not only by the regu- 
larity of its forms, the perfection of its surfaces and angles, its trans- 
parency, and its brilhancy, but also by the manner in which it grows, 
heals its wounds, is dissolved, and modified under the influence of the 
inclosing medium. ‘To some authors the crystal, from certain points 
of view, appears analogous to living forms, and seems to undergo 
a sort of evolution. 
Its formation, its growth, the variations of the faces under the 
influence of the inclosing medium, have been the object of numerous 
researches which have greatly modified our conceptions regarding 
them. The purpose of this article is to show the present state of our 
knowledge concerning these diverse and interesting questions of 
crystallogeny. 
I 
As early as the seventeenth century Leeuwenhoek, who examined 
under the microscope everything that in his time lent itself to this 
line of observation, followed the formation and growth of the erys- 
tals of various substances (as sugar, tartar, sea salt, etc.). He was 
led to conclude that the cubic crystals of sea salt are formed of other 
minute cubes, themselves made up from cubes, the existence of which 
one has to accept through analogy with what is seen, since they are 
invisible under any magnifying power. Later, Baker, Ledermiiller, 
and others also examined under the microscope the branched and 
varied forms that appear when a substance crystallizes on a sheet of 
glass; but it is to Nicholas Le Blanc that we owe the first systematic 
and effective researches in crystal genesis, and particularly in the 
variation of the form. In his very interesting work “ De la Cristallo- 
technie ” he gives methods for the preparation of crystals, and in 
particular does he set forth the process of renewing the solution, 
“Translated by permission from Revue Scientifique, Paris, 48th year, No. 3, 
January 15, 1910. 
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