Barker ] 44:1) [May 7, 



geology of the country south of Lake Erie, suggested by the 

 work of the IsTew Geological Survey of Pennsylvania ; the 

 most important of these changes, namely, the adoption of an 

 east and west strike for a northeast and southwest strike, 

 being necessitated by the probability that most of the expo- 

 sures of conglomerate throughout Warren, Venango, and 

 Crawford Counties in Pennsylvania, and Cattaraugus and 

 Chautauque Counties in New York, belong to a horizon 200 

 feet below that of the Great Conglomerate, No. XII, the 

 base of the Productive Coal Measures. 



Dr. Cresson referred to the discussion of thermo-electric 

 currents at the last meeting to state his own opinion that it 

 is not needful to have two metals, or an unhomogeneous 

 mass of one metal for the exhibition of such currents. He 

 had found water alone to be a sufficient medium for the pro- 

 duction and exhibition of the phenomena under discussion. 



The minutes of the last meeting of the Board of Officers 

 and Members in Council were read. 



Pending nomination, Ko. 780, and new nominations, No. 

 781 and 782 were read. 



And the meeting was adjourned. 



CONTRIBUTIONS FROM THE PHYSICAL LABORATORY OF THE 

 UNIVERSITY^ OF PENNSY^LVANIA. 



No. I. 



A NEW VERTICAL-LAN TEKN GALVANOMETER. 



By George F. Barkeb, M.D., Professor of Physics. 



{Bead before the American PJiilosopJiical Society, May 1th, 1875.) 

 Desiring to show to a large audience some delicate experiments in 

 magneto-electric induction, in a recent lecture upon tlie Gramme machine, 

 a new form of demonstration galvanometer was devised for the purpose, 

 which has answered the object so well that it seems desirable to make 

 some permanent record of its construction. 



Various plans have already been proposed for making visible to an 

 audience the oscillations of a galvanometer needle ; but they all seem to 

 have certain inherent objections which have prevented them from coming 

 into general use. Perhaps the most common of these devices is that first 



