AT HIGH PEESSURES BY OPTICAL METHODS. 
121 
atmospheres—a small hand-compressiiig pump for filling the larger compressor with 
oil at pressures of about 800 atmospheres, a steel vessel, to which hotli compressors 
and the pressure-homb holding the substance are connected by means of drawn-steel 
capillary tubes of 7 mm. outer diameter and 1 mm. bore, and a high-pressure valve, by 
which the smaller compressor, together with its manometers, can be shut off from the 
rest of the apparatus when working at pressures above 600 atmospheres. The whole 
of this apparatus is fixed to a heavy oak bench. The various parts are connected as 
shown by the diagram (fig. l), thus forming a pressure-plant which may be used for 
any kind of high-pressure work. The large compressor for high pressures (A, fig. l) 
is of the Cailletet type, but made entirely of steel, and is of much larger size 
than the ordinary Cailletet apparatus. It is very similar to those used by Tammann 
in his high-pressure experiments.^" As in the case of the Cailletet apparatus, a 
plunger is forced into a cylindrical compressing cliamber in the central steel block A by 
a powerful screwing gear. Oil is pumped into this compressing chamber by means of 
the compressing pump B, which is connected to the oil reservoir C. D is a valve by 
which the compressing chamber is shut off from the pump B before the compressor is 
worked. By the valve E a fine capillary channel, which connects the compression 
chamber witli the high-pressure manometer F and with the pressure-transmitting 
pipe G, can be shut off from these, thus leaving only the manometer connected with 
the pressure-transmitting pipe and the pressure-bomb, in which the investigation is 
* G. Tammann, ‘ KristallLsieren u. Sclimelzen,’ p. 195. 
VOL. CCXII.—A. 
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