236 Intelligence and Miscellaneous Articles. 



This result is only a confirmation of my theory of electric inertia, 

 since the condition of equal distribution (equal superficial tension), 

 and symmetrical, is not fulfilled when induction-apparatus is used. 

 In fact the tension of the current after the opening and after the 

 closing of the inducing current is not the same, and the charge of 

 the symmetrical conductor is successively positive and negative ; 

 the superficial tension cannot be none, nor even equal, since a cer- 

 tain time is required for the two electricities to combine after two 

 alternate unequal discharges, considering the tension and the nature 

 of the electricity. The tension at the part of the symmetrical con- 

 ductor furthest from the point of discharge will be quite different 

 from that at the part nearest to the conductor of the Ruhmkorff ; 

 and the condition of equal superficial tension at every point of the 

 symmetrical conductor is not fulfilled. Failing this essential con- 

 dition, there will be an action nearly equal to the difference of ten- 

 sion of the sparks of opening and of closing. 



To show the influence of the symmetrical distribution, I put 

 symmetrically round a gold-leaf electroscope a rectangular copper 

 wire ; the electroscope and the wire are placed upon the brass plate 

 of another electroscope (with straws instead of gold leaves), larger 

 and less sensitive. From the conductor of an electrical machine 

 strong sparks go to one of the angles of the wire ; the upper elec- 

 troscope shows not a trace of tension, while the straws of the large 

 electroscope below are strongly affected. 



If the experiment be modified by placing the knob of the upper 

 electroscope not symmetrically in relation to the middle points of 

 the sides of the conductor, there will be seen a movement of the 

 gold leaves at every discharge from the conductor of the machine. 

 The greater this defect of symmetry, the more sensible will be the 

 action. — Comptes Ilendus cle VAcademie des Sciences, vol. lxxv. p. 1765. 



ON THE HEAT OF TRANSFORMATION. BY M. J. M0UT1ER. 



A substance may present itself at the same temperature in two 

 different states, which we will call M and M'. In passing from M 

 to M' a kilogramme of the substance absorbs a quantity of heat Q, 

 which we will call heat of transformation. Let us suppose that in 

 both conditions the substance can be vaporized, and that the ten- 

 sions p and p of the vapours at the same temperature are unequal ; 

 we propose to determine a relation between the heat of transforma- 

 tion Q and the tensions p and p'. 



Let u and u' be the specific volumes of the substance in the states 

 M and M', v and v' the specific volumes of the vapours given by M 

 and M', L and L' the heats of vaporization. 



Let us conceive the following cycle of operations effected at a 

 constant temperature : — 



(1) The substance passes from the state M to M' under a con- 

 stant pressure 7r ; it absorbs the quantity Q of heat. The quantity 

 of heat consumed by external work is A.n(u — u), A being the heat- 



