Crystallogenesis. — Hensoldt. 377 
now appears to act as a separate bar-magnet, and while some 
unite at right angles, others range themselves, in close contact 
side by side, and form a symmetrical wall. Layer is piled on 
layer, each little rod falls mechanically into its proper place — 
no regiment of soldiers could "form up" with greater precision, 
and before we have time to realize the strangeness of the 
spectacle, the field is studded with little cubes of exquisite 
beauty. 
What we have seen here in an evaporating drop of chloride 
of sodium may be observed in any other saline substance 
which we allow to crystallize under the microscope, with the 
sole difference that the diameter of the globules and the form 
of the ultimate crystals vary according to the nature of the 
substances employed. That in the formation of minute spher- 
ical bodies we have the first visible manifestation of crystal- 
line activity, was announced as early as 1839 by H. F. Link^ 
a German microscopist, who detected the globule in evapor- 
ating liquids, which is surprising, considering the inferiority of 
objectives at that period. He expressed the opinion that they 
were hollow, but Vogelsang in his admirable work "Die Krys- 
talliten," published in 1875, clearly demonstrated their mas- 
sive character. This work — a masterpiece of careful observa- 
tion and originality — should be read and re-read by every pe- 
trographer, mineralogist, chemist, physicist, in short by every 
student of natural science. 
Vogelsang, in his experiments, employed a solution of sul- 
phur in bisulphide of carbon, which he mixed Avith a certain 
quantity of Canada balsam, in order to retard the crystallizing 
process. The mechanical resistance, offered by the viscous bal- 
sam, prevented the globulites from moving about with their ac- 
customed alacrity,their evolutions could be slackened, acceler- 
ated or arrested at pleasure, so that it now became possible to 
observe every phase in that wonderful series of changes which 
lead from apparent chaos to extreme crystalline symmetry. 
We have abundant proof that the changes here described 
must occur in precisely the same order whenever a moUcnxnxn- 
eral substance slowly solidifies, and in sections prepared from 
many vitreous rocks, such as obsidians, pitchstones, perlites, 
tachylites, etc., we observe every species of molecular arrange- 
ment, from the primary globulite to the complete crystal. 
** "Ueber die erste Enstebung der Krystalle." 
