8o 



THE POPULAR SCIENCE MONTHLY. 



a portion of it, in the liquid state, is seen in the glass tube, and spurts 

 out of the orifice on the apparatus being inclined. 



A sufficiently clear idea of M. Pictet's method can be had from the 

 above diagram and description; but, as yet, the reader can hardly 

 imagine what the apparatus looks like. Fig. 2 (after a photograph) 



Fig. 2. Pictet's Apparatus (from a Photograph). 



and Fig. 3 will supply this deficiency. Fig. 2 is a general view of 

 Pictet's grand liquefaction apparatus, as it stands in his establishment 

 at Geneva; and Fig. 3 exhibits the same in section. This apparatus 

 possesses considerable size ; for instance, the head of a man standing 

 would be on a level with the manometer seen near the letter H in the 

 engraving. 



The perfected apparatus as shown in Fig. 2 diffoi ., in sundry respects 

 from the diagram Fig. 1, as will be seen at a gl ; >. One essential 

 difference consists in the arrangement of the liquefy vjtion apparatus 

 proper, Fig. 4. Here D is an iron shell (or retort), with walls 35 mil- 

 limetres in thickness ; it contains 700 grammes of chlorate of potash 

 when oxygen is the gas to be liquefied. Its orifice communicates with 

 an iron tube five metres in length, 214 millimetres internal diameter. 

 This tube, bent as in the figure, is closed at both ends, but one end 

 may be opened by means of the cock IE. A Bourdon manometer, 

 graduated to 800 atmospheres, shows the inside pressure. The tube 

 c JEJ, in which the disengaged oxygen is compressed, is completely 

 immersed in liquid carbonic acid, which, by the mechanism of the 



