UPON GASES AND LIQUIDS. 577 



leaving a small space for its play. The vessel was 41 milliras. in 

 height and 93 millims. in length in the equatorial direction ; in- 

 the axial direction, 4'5 millims. in breadth in the middle, and 40 

 millims. in breadth at the two ends; it was everywhere closed 

 air-tight, except that a glass tube, 1 millim. in diameter, which 

 was placed horizontally in the equatorial plane, was let into the 

 middle of one of the two almost square walls. After the tem- 

 perature was found to remain constant at 53° F., the vessel was 

 shghtly warmed by the contact of the hand ; and then, to con- 

 fine the air inside, a drop of alcohol was placed at the orifice 

 of the tube. On withdrawing the hand, the drop ran into the 

 tube and settled near the vessel. The magnetism was then ex- 

 cited by closing a circuit of twelve Grove's elements, and at the 

 same instant the drop of alcohol was driven 3 millims. nearer to 

 the orifice of the glass tube ; and after some time, when it had 

 become stationary, the circuit was again opened ; it then returned 

 to exactly the original position, the latter movement being more 

 rapid than the former. Thus, in consequence of the diamagnetic re- 

 pulsion, the air became expanded by the electro-magnet, and on the 

 disappearance of the magnetism it returned to its original volume. 



58. The vessel described in the preceding paragraph can be 

 opened and closed in the middle of the other lateral wall, that 

 which is opposite to the one in which the glass tube is let in, 

 and thus may be filled with antj kind of gas. Hence these can 

 be tested as to their diamagnetism in the same manner as the air. 



Lastly, on the same principle, we can determine the influence 

 of heat upon the diamagnetism of gases ; and we are not only 

 able to observe the diamagnetism of any gases at a given tem- 

 perature, but we can also measure it. 



59. Since, according to the other methods of determination, 

 any gas which is not enclosed can only be experimented upon 

 in the air or some other gas by this means, independently of 

 admeasurements being then out of the question, we can only 

 arrive at relative determinations. We can, in that case, only 

 suppose that air, with all other gases, is diamagnetic. The phae- 

 nomena would remain the same in all experiments of the kind, 

 if the air and all gases, instead of being diamagnetic, were mag- 

 netic, supposing however that those whicli in reality are most 

 powerfully diamagnetic were least magnetic. 



60. The results obtained in par. 57 appeared to me remarkable 

 in many respects, and especially because they directly prove 



