On Current Curves. 255 



Professor H. Or. Seeley's objection fco tlie importation of the Amphi- 

 bian plan in explanation of a part of the Plesiosaurian shoulder girdle, 

 of which other parts have been explained by reference to the Chelonian 

 plan of construction, has not, I venture to think, great weight, since, 

 of the early Reptilia, from the time when their remains first began 

 to be studied, it has been a frequent remark that their skeletons 

 comprise structural arrangements which, in existing animals, are now 

 found separately. Moreover, it is thought by some of the ablest 

 comparative anatomists that the Chelonian skeleton shows closer 

 approach to the Amphibian than is to be found elsewhere. 



" On Current Curves/' By Major R. L. HIPPISLEY, R.E. 

 Communicated by Major MACMAHON, F.R.S. Received 

 May 12, Read June 2, 1892. 



(Abstract.) 



1. The object of the present paper is to show how to determine 

 expressions for the current in circuits having iron cores, similar to 

 the well-known equations 



i = ~(l-e-^l L ) 

 R 



Tjt 



and i --- s'm(pt 6) 



3 - 2 



for circuits without iron, which will enable the current curves to be 

 pre- determined by calculation and plotted independently of experi- 

 ment. 



In circuits with iron cores the value of ~- occurring in the original 



at 



differential equations 



E-^ = K; .................. a). 



dt 



Esmp; ^*=Ri ........... ...... (2) 



dt 



continually alters as i changes. If we could obtain an expression for 



in terms of i, the substitution of this expression in (1) and (2) 

 dt 



should lead us to the required result. But, though such an expres- 

 sion can be found, its substitution will generally lead to differential 

 equations which cannot be solved by known methods. 



2. In the case represented by (1), where the applied E.M.F. is 

 constant, we can determine by Lagrange's formula of interpolation 



VOL. LIT. S 



