156 Mr, W. E. Grove, on Inferences from [Jan. 25, 



cordant; so that without giving any opinion on their different 

 results, this question may be considered at present far from settled. 

 M. Regnault himself does not give the law by which the ratio of 

 heat varies with reference to the pressure, and is still believed to be 

 engaged in researches on the subject, one involving questions of 

 which experiments on the mechanical effects of elastic fluids seem 

 to offer the most promising means of solution. 



One of the greatest difficulties which had presented itself to 

 Mr. Grove's mind, with reference to the theory of Carnot, had 

 been one of analogy, derived from the received theories of elec- 

 tricity. Many electrical cases might be cited in which no electricity 

 is supposed to be lost, though a certain mechanical effort is produced 

 by the electricity ; if, for instance, a ball vibrates between a posi- 

 tively and negatively electrified substance, none of our electrical 

 theories lead us to believe that any difference in the actual amount 

 of electricity transferred would be occasioned by the ball being 

 attached to a lever which would strike a wheel or produce any other 

 mechanical effect. 



In preparing this evening's communication an experiment had 

 occurred to him, which, though performed with imperfect apparatus 

 and therefore requiring verification, does, as far as it goes, support 

 the view derived from the negation of perpetual motion, viz. that 

 when electricity performs any mechanical work which does not 

 return to the machine, electrical power is lost. The experiment is 

 made in the following manner. A Leyden jar of one square foot 

 coated surface has its interior connected with a Cuthbertson's elec- 

 trometer, between which and the outer coating of the jar are a pair 

 of discharging balls fixed at a certain distance (about ^ an inch 

 apart). Between the Leyden jar and the prime conductor is in- 

 serted a small unit jar of nine square inches surface, the knobs of 

 which are 0*2 inch apart. 



The balance of the electrometer is now fixed by a stiff wire 

 inserted between the attracting knobs, and the Leyden jar charged 

 by discharges from the unit jar. After a certain number of these, 

 (22 in the experiment performed in the theatre on this occasion,) 

 the discharge of the large jar takes place across the i-inch in- 

 terval ; this may be viewed as the expression of electrical power 

 received from the unit jar. The experiment is now repeated, the 

 wire between the balls having been removed, and therefore the 

 ' tip ' or the raising of the weight, is performed by the electrical 

 repulsion and attraction of the two pairs of balls ; at 22 discharges 

 of the unit jar the balance is subverted, and one knob drops upon 

 the other, but no discharge takes place, showing that some electricity 

 has been lost, or converted into the mechanical power which raises 

 the balance. By another mode of expression the electricity may 

 be supposed to be masked or analogous to latent heat, and would 

 be restored if the ball were brought back, without discharge, by 

 extraneous force. 



