SOLIDIFICATION BY PRESSURE.

M. Amagat has succeeded in solidifying various liquids, by compressing them in cylinders of bronze and steel.  He has also photographed the crystals after crystallization, by means of a ray of electric light traversing the interior of the vessel by glass cones serving as panes.  The stages of crystallization can be observed in this way with chloride of carbon, and it is seen that the process varies with the rapidity with which the pressure is produced.  If rapidly, a sudden circlet of crystals gathers round the edge of the luminous field, and grows to the center.  The pressure being continued, the field becomes obscure, then transparent.  As the pressure is diminished the reverse takes place, and the liquid state is reproduced.  M. Amagat finds that chloride of carbon solidifies at 19.5 deg.  Cent., under a pressure of 210 atmospheres.  At 22 deg.  Cent., benzine crystallizes with a pressure of about 900 atmospheres.

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