Intelligence and Miscellaneous Articles, 447 



stopped by difficulties which led me to suspect at once that this 

 body (unknown, moreover, in the solid state) was solidified by 

 pressure ; I forthwith made the following experiment, which is only 

 the reverse of that of Mousson with ice. 



The liquid is compressed in a bronze cylinder, of which the upper 

 part is closed by a kind of plug of soft iron, which is at the same 

 time the prolongation of the pole of an electromagnet. In the 

 liquid a small cylinder of soft iron is free to move, sinking by its 

 own weight, and which, at the moment of closing the current, is 

 attracted and, traversing the liquid, strikes the plug. Under a 

 sufficient pressure, the noise produced by the collision, which is 

 audible at several metres distance, ceases to be heard ; it is heard 

 anew as soon as the pressure is sufficiently diminished. The 

 pressure at which the little cylinder ceased to move was, in this 

 experiment, about 1500 atmospheres. 



I have since carried out the following arrangement, which has en- 

 abled me not only to see the solidification take place, but also to obtain 

 perfectly regular crystals and to photograph them. The chloride of 

 carbon is enclosed in a steel chamber having, (one in front the 

 other behind, s two horizontal holes formed by small cones of an- 

 nealed glass, making a smooth joint by means of a conical envelope 

 of very thin ivory. A ray of electric light traverses these two cones 

 (and the liquid compressed between them) parallel to their common 

 axis, and falls upon a telescope fixed in the same direction : we 

 can, under these conditions, easily follow the course of the phe- 

 nomenon. The apparatus is, moreover, arranged in such a manner 

 as to permit of its being maintained at a constant temperature by a 

 current of water, by ice, or by a freezing-mixture. 



The observations are made by bringing into focus the back face 

 of the cone turned towards the telescope ; the solidification in taking 

 place presents very different appearances according to the degree 

 of quickness with which the pressure is produced. If this is done 

 rapidly, there is seen to spring up suddenly at the periphery of the 

 luminous field a wreath of crystals more and more closely packed 

 and opaque ; this quickly and regularly spreads to the centre, 

 which soon becomes reduced to a luminous point and disappears in 

 its turn. If we continue to compress it, the field remains for some 

 time completely obscured, then little by little it is illumined and the 

 mass becomes transparent again : one could believe that it had 

 again become liquid. If the pressure be then gradually diminished, 

 the tangle of crystals reappears and the field again becomes obscure ; 

 at length, the pressure diminishing continuously, the light reap- 

 pears anew, and the crystals dissolve and dislodge themselves from the 

 mass, they are seen to sink across the liquid portion ; thus they are, 

 agreeably to hypothesis, heavier than the latter. 



By taking certain precautions it is possible to obtain and to pre- 

 serve for some time crystals detaching themselves very regularly 

 from the portion which remains liquid ; these can then be photo- 



