346 



'''~ 8 1-^,7'" 



is fiiriilated in the first conductor. The electi-oniotive force in that 

 conductor amounts to Zi, = I^ . W,. In consequence of the circu- 

 lation of the quantity of electricity e,, the generator of the current 

 yields, besides the Joui^k heat, the quantity of energy — -fcV'n which 

 amounts to : 



tnffkf.I.R' 



— E.fi, = . 



8c' 



We lind in the same way that after subtraction of the Joui.K 



heat, an equal amount of energy is yielded by the second generator 



of current. Together the total quantity of energy yielded by the 



generator of current, amounts therefore to: 



1 



which corresponds with the value A -\- LT, required for the work 

 of the ponderomotive forces and the increase of the magnetic energy. 



Chemistry. — "Molecuhir-Allotrojn/ mul Fhii.si'-A//ofro/t;/ in Oiyanic 

 Chemistry y By Prof. A. Smits. (Comnuinicated by Prof. J. 



D. VAN DEK W.\AIS). 



1. Snrteij of orgn/iic pseiulo-si/.stems. 



I have indicated the appearance of a substance in two or more 

 similar phases by the name pliase-allotropy, and the occurrence of 

 different kinds of molecules of the same substance by the name of 

 moh'cular-iiUoti-opji. It may be assumed as known that one of the 

 conclusions to which the theory of allotropy leads, is this that phase- 

 allotropy is based on molecular-allotropy. 



The region in which the existence of molecular allotropy is easiest 

 to demonstrate is the region of organic chemistry, and I think that 

 I have to attribute this fact to this that the velocity of conversion 

 between the different kinds of molecules which present the pheno- 

 menon of isomery or polymery, is on the whole much smaller in 

 organic chemistry than in anorganic chemistry ; in organic substances 

 it seems even not perceptible in many cases. The substances, for 

 which this is, however, the case, and which were formerly called 



