266 



NA TURE 



{Jan, 31, 1878 



This permitted a water-tight junction with a corresponding 

 end of a cold-drawn tube of copper of great strength. A 

 similar end-piece was attached to the other extremity of this 



Fig. I. — Two of I)r Andrews's lubes on a stand as iu use 



copper cylinder, and in the centre was a fine screw most 

 carefully made and fitted, seven inches long, and packed 

 so as to resist a pressure of 400 atmospheres or more. 



Fig. 2. — Section of Tube. 



Fig. 3 — Arrangements for Utilising 

 Low Temperatures. 



When low temperatures as well as high pressures were 

 required, the tube was bent, as shown in Fig. 3, and 

 inserted in a freezing mixture. 



In all these tubes the pressure is produced by screwing 

 up the mercury into the capillary tube. 



We have next to consider the phenomena which Dr. 

 Andrews observed, taking carbonic acid as an example. 



On partially liquefying the gas by pressure and charging 

 the temperature, the surface of demarcation between the. 

 liquid and the gas became less and less distinguishable, 

 the tube seemed to be filled with a homogeneous fluid 

 which, when the pressure was suddenly diminished, or the 

 temperature slightly lowered, broke up into striae. Fig. 4. 



A cloud was also formed if the temperature were 

 allowed to fall a little below the "critical point" 3o°"92 C, 

 showing the formation of liquid particles, Fig. 5. 



We may now pass to M. Cailletet's method and the 

 phenomena he observes. Fig. 6, for which we are indebted 

 to the courtesy of the editor of La Nature, represents the 

 great apparatus which M. Cailletet has constructed at his 

 works of Chitillon-sur-Seine. 



The apparatus is composed of a hollow steel cylinder 

 A solidly fixed to a cast-iron frame by means of the 

 hoops B B. A cylindrical shaft of soft steel acting the 

 part of a plunger enters this cylinder, which is filled 

 with water. The opposite extremity of the shaft is 



Fig. 4.— Striae. 



Fig. 



-Cloud. 



terminated by a square-threaded screw, which traverses 

 the bronze nut F, fixed in the centre of the fly-wheel 

 M. According to the direction given to the fly-wheel 

 by means of the handles with which it is provided, 

 the plunger may be advanced into or withdrawn from 

 the axis of the body of the pump. A leather packing 

 prevents the compressed liquid from escaping from the 

 cylinder. 



In order to introduce the water or the liquid to be com- 

 pressed, it is poured into the glass vessel G, which is 

 in communication with the interior of the apparatus ; a 

 steel screw with conical point closes the narrow pipe 

 through which the liquid passes. This screw is termi- 

 nated by a small fly-wheel o, with handles. This arrange- 

 ment permits of suddenly expanding the compressed 

 gases, and seeing the cloud produced in the capillary tube 

 where the gas under experiment is contained. (This tube 

 is represented in the centre of the glass envelope, in!) The 

 cloud is formed under the influence of the external cold 

 produced by the sudden expansion, a certain sign of the 

 liquefaction or even of the solidification of the gases re- 

 garded hitherto as permanent, a is a hollow steel reservoir 



