520 Geological Society. 



Die Erdstrbme im Deutsclien Reichstelegraphengebut und ihr Zusam- 

 menhang mit den Erdmagnetischen Erscheinungun. Im Auftrage 

 des Erdstrom-Comite's des EleJctrotechnischen Vereins Bearbeitet 

 und Herausgegeben von Dr. B. Weinstein. Mit einera Atlas Ent- 

 haltend 19 Lithographirte Tafeln. Braunschweig: Y. Vieweg 

 und Sohn, 1900. Pp. vi+78. 



Iis T 1881 the Elektrotechnischer Verein appointed a committee to 

 investigate the phenomenon of earth-currents. After the necessary 

 preliminary investigations, a regular series of observations was- 

 commenced in 1883 on two underground cables, whose directions 

 were roughly north-and-south and east-and-west respectively. 

 The first cable was one connecting Berlin with Dresden, the second 

 ran from Berlin eastwards as far as Thorn. The cables were- 

 placed at the disposal of the committee by the postal authorities. 

 In the circuit of each cable was included a registering apparatus, 

 the ends of each cable being earthed. The observations were con- 

 tinued until 1891, when the cables could no longer be spared. The 

 mass of observations accumulated during that period has been 

 subjected to a careful analysis by Dr. Weinstein, and the present 

 pamphlet and atlas are the outcome of his labours. Besides an 

 account of the various periodic changes which earth-currents under- 

 go, and which appear to be chiefly influenced by the position of the 

 sun, Dr. "Weinstein gives an account of the corresponding periodic 

 changes in the intensity of the earth's magnetic field, and discusses 

 the connexion between the two. He states it as his opinion that 

 almost the whole of the diurnal variations in the earth's magnetism 

 are really due to the magnetic effect of earth-currents. At a 

 time when the attention of physicists is centred on the subject 

 of magnetic records in connexion with the somewhat heated dis- 

 cussion which is now being carried on between the advocates of 

 magnetic observatories and those of electric- traction systems with 

 uninsulated rail-return, the present account of a series of simul- 

 taneous magnetic and earth-current observations should prove of 

 considerable interest. 



XL VI. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from p. 168.] 



June 20th, 1900.— J. J". H. Teall, Esq., M.A., F.R.S.. President, 



in the Chair. 

 The following communications were read : — 



1. ' On the Skeleton of a Theriodont Reptile from the Baviaaus 

 River (Cape Colony).' By Prof. H. G. Seeley, F.R.S., F.L.S. r 

 V.P.G.S. 



2. ' Fossils in the Oxford University Museum. — IY. : Notes on 

 some Undescribed Trilobites.' By H. H. Thomas, Esq., B.A., F.G.S. 



3. ' On Radiolaria from the Upper Chalk at Coulsdon (Surrey).- 

 By W. Murton Holmes, Esq. 



