268 



NATURE 



\7an. 31, 1878 



capable of supporting a pressure of from 900 to 1,000 

 atmospheres ; it is connected with the compression appa- 

 ratus by a capillary metallic tube. The water, under 

 the action of the piston, arrives in this reservoir, a, and 

 acts upon the mercury which compresses the gas. b repre- 

 sents the tube which connects this with the glass intended 

 to contain the gas under experiment. A nut serves to 

 fix this piece to the upper part of the reservoir. Fig. 7 

 shows this arrangement in half-size. 



m is a glass cover containing a cylinder of the same 

 material, in the middle of which is a small tube in which 

 the liquefaction of the gas takes place. This capillary 

 tube may be surrounded with refrigerating mixtures or 

 with liquid protoxide of nitrogen. The exterior cover, tn, 

 concentric with the first, and containingsubstances strongly 



absorbent of moisture, prevents the deposit of ice or vapour 

 on the cooled tube in which the experiments are made. 

 ^ is a cast-iron tablet intended to support the reservoir, 

 a ; the screws, d d, enable the reservoir to be raised or 

 lowered for the spectroscopic examination or the pro- 

 jection of the exoeriments. An arrangement, S, unites 

 the capillary metallic tubes which transmit the pressure to 

 the various parts of the apparatus. N is a modified 

 Thomasset manometer verified by means of an air mano- 

 meter established on the side of a hill near the labo- 

 ratory of Chatillon sur-Seine. n' represents a glass 

 manometer which serves to control the indications of the 

 mercury apparatus. 



It is a fortunate thing that the students of science in 



Fig. 7, Fig. 8 



Fig. 7.— Glass tube with thick sides in which the liquefaction of the gas ts is effected in M. Cailletet's apparatus. The gas is compressed in the tipper 

 part of the tube by the ascent of a column of mercury placed in connection with a screw-press acting on a mass of water. It condenses in a liquid 

 drop or into mist under the action of expansion. This glass tube is enveloped in an envelope of the same substance containing the refrigerating 

 mixture. See the centre of the tube »t in Fig. z. Fig. 8. — Small apparatus for the liquefaction of gases. 



France have not been forgotten by M. Cailletet. He 

 has not only devised the instrument above described 

 for his own work, but he has occupied himself with a 

 small lecture or laboratory apparatus which M. Ducretet 

 has constructed according to his directions. It is an exact 

 copy of the part, a, b, m of the apparatus of Chatillon- 

 sur-Seine. The bell-glass alone is modified. The screw- 

 press is, moreover, replaced by an easily-worked pump. 

 In Fig. 8 t't is a glass tube filled with the gas to be 

 compressed ; the tube has been traversed by the gas 

 until air has been entirely excluded ; for this purpose 

 it is placed in a horizontal position. When it is 



filled with the gas to be experimented on it is her- 

 metically sealed at its extremity, p, closed with the 

 finger at the other end, and introduced vertically into the 

 iron apparatus as represented in the figure. It is inserted 

 into a cylindrical cistern containing mercury. The upper 

 part of the tube is enveloped in a glass envelope, M, 

 filled with a refrigerating mixture. The whole is en- 

 veloped in a glass jar, G. The tube, T u is connected 

 with a compressing pump, which is worked with the 

 hand. The water compressed by the pump acts on 

 the upper part of the mercury indicated in the figure by 

 horizontal lines. This mercury is driven back into the 



