438 



dated Philadelphia, May 3 ; Mr. W. A. Ingham, dated Phila- 

 delphia, April 19 ; Prof. S. P. Langley,. dated Allegheny, 

 Pa., April 19 ; Prof. Frederick Prime, Jr., dated Lafayette 

 College, Easton, April 19, and Prof. Rossiter W. Raymond, 

 dated New York, April 21. 



A letter of acknowledgment was received from the Royal 

 Society, dated Edinburgh, Dec, 1871 (XIV. i. iii. Proc. 

 83-87). 



A letter of envoy was received from the l^ondon Meteor- 

 ological Office of the Royal Society dated April, 1875. 



Donations for the Library were received from the Royal 

 Academies at Berlin and Turin ; the Observatories at Green- 

 wich, Cape Town, and Oxford ; the Geographical Society 

 and Editors of Revue Politique at Paris ; the Royal Geo- 

 graphical and Royal Astronomical Societies and Editors of 

 " is^ature " at London ; and Literary and Philosophical So- 

 ciety, Liverpool ; Natural History Society, of Northumber- 

 land, at Newcastle-on-Tyne ; Royal Society and Royal Botan- 

 ical Garden at Edinburgh ; Royal Geological Society at 

 Dublin; Essex Institute; Museum of Com|)arative Zoology, 

 at Cambridge, Massachusetts ; Boston Society of Natural 

 History; American Antiquarian Society at Worcester; Sil- 

 liman's Journal ; Prof. J. D. Dana; Editors of the American 

 Chemist ; Columbia College School of Mines ; New Jersey 

 Historical Society ; Editors of the Medical News and Penn 

 Monthly ; College of Pharmacy ; Dr. C. M. Cresson ; Mr. 

 Lorin Blodget; the U. S. Coast Surv^ey ; U. S. Engineer 

 Department ; and U. S. Department of the Interior, 



Dr. Barker exhibited the performance of his new arrange- 

 ment of the galvanometer for lecture illustration, describing 

 the successive contributions to its perfection made by Sax- 

 ton, Poggendorf, Sir "Wm. Thompson, President Morton, and 

 Prof. Mayer. 



A discussion follow^ed on the galvanic currents in rocks, 

 and the magnetism of the earth. 



Mr. Blodget referred to a former communication to the 

 Society on the subject of the vertical descent of air in the 



