180 [Jan 17 



xVfier we got down 000 feel the atmosphere is not quite so clear us it is 

 nearer to the surface." 

 [fyour society can suggest further tests I will be glad to make them. 

 I am very respectfully your obedient servant, 



P. W. SHEAFER. 

 To the American Philosophical Society, 

 Fifth Street, near Chestnut, Phila. 



Mr. B. Britton exhibited a small and useful specimen-rock 

 crusher for laboratory use, with mortar and pestle, and de- 

 scribed its value in the saving of time and labor. 



Mr. Lesley exhibited a proof sheet of Mr. J. F. Carll's col- 

 ored map of the preglacial water basins of North-western 

 Pennsylvania, prepared for the illustration of his forthcom- 

 ing third Report of Progress in the Survey of the Oil 

 Regions. 



Mr. Marks exhibited and explained a new link-work, 

 which he had invented for the use of his students in de- 

 scribing arcs of epicycloid curves, and which can be made 

 practically useful for plotting the outlines of the teeth of 

 wheels. He also exhibited specimens of other Peaucellier 

 cell forms. 



On motion, Mr. Lesley was elected Librarian for the en- 

 suing year. 



The Standing Committees for 1879 were then appointed, 

 as follows : 



Finance. 



Mr. Frederick Fraley, 



Mr. E. K Price, 



Mr. Benjamin V. Marsh. 



Publication. 



Dr. John L. LeConte, 

 Dr. Daniel M. Brinton, 

 Dr. McQuillen, 

 Prof. E. Thompson, 

 Dr. C. M. Cresson. 



