Intelligence and Miscellaneous Articles. 373 



Palaeontology as regards Invertebrate Animals," by Prof. H. A. 

 Nicholson, M.D., D.Sc, F.G.S. After pointing out the false 

 position taken by those who would suppress Palaeontology as an 

 independent branch of Biology, he proceeds to mention the dis- 

 covery of the probably Forarniniferal structure of some oolitic 

 grains, — of the probable occurrence of Radiolaria in Ordovician 

 chert of South Scotland, and of the possible proof of fossil Radio- 

 larian deposits being of deep-sea origin, — of the recent advances 

 in our knowledge of fossil Sponges, — of the Strom atoporidae and 

 the true Hydrocorallines, — of the true Coral groups and other 

 Coelenterata, — the Monticuliporoids also, and the fossil Echino- 

 derms, Annelides, Crustaceans, Arachnides, Insects, and Polyzoa. 

 The Brachiopoda and Mollusca proper are slightly touched on, 

 except the fossil Pteropods, which are more especially treated of. 

 In conclusion Dr. Nicholson states " that the ascertained facts of 

 Palaeontology indicate, with an ever-increasing clearness, the exist- 

 ence of some general law of Evolution, by the operation of which 

 new forms of life have been successively introduced upon the earth. 

 As to the precise modus operandi of this general law, Palaeontology 

 does not, in my opinion, at present aiford a decisive answer. That 

 one great factor in the process has been the operation of 'Natural 

 Selection/ as explained and defined by Darwin, does not, I think, 

 admit of reasonable doubt. That 'Natural Selection' has been 

 the sole agency at work is, however, a different and more doubtful 

 point ; and Palaeontology, at any rate, does not seem to me to be 

 yet in the position to supply the final solution to this most difficult 

 and complex problem." 



XL. Intelligence and Miscellaneous Articles. 



ON ELECTRICAL VIBRATIONS IN STRAIGHT CONDUCTORS. 

 BY PROF. J. STEFAN. 

 npHE distribution of a constant electrical current in a conductor, 

 ■*■ or its branching into several conductors, takes place in such a 

 manner that, for the same strength of the total current, the disen- 

 gagement of heat, according to Joule's law, is a minimum. This 

 principle has been demonstrated by Kirchhoff for conductors of 

 any given shape. It holds, however, only when the individual parts 

 of the conductor contain no special electromotive forces ; it does 

 not hold therefore for variable currents in which inductive actions 

 occur in the conductors. 



In currents of rapid variability, particularly with periodical 

 currents of very high number of vibrations, the influence which the 

 resistances exert on their regulation becomes less in comparison 

 with those of the inductive actions ; and with periodic currents to 

 the greater extent the higher the number of vibrations. In solving 

 many questions relating to the behaviour of such currents we can 

 entirely neglect the resistance of the conductors, and can use 

 equations which hold for currents in conductors without resistance. 

 G. Lippmann was the first to direct attention to these equations 

 and their application. 



Phil. Mag. S. 5. Yol. 29. No. 179. April 1890. 2 F 





