76 PROCEEDINGS. 



piece, the material of this bar must be ascertained by previous 

 experiments, to be perfectly elastic, so that its extensions are 

 strictly proportional to the pull, and therefore to the pull on the 

 test piece, and moreover it should be of such an area that its 

 limit of elasticity occurs only at a load greater than that which 

 will break the test piece. By a simple arrangement, a very 

 light pointer is made to swing about an axis through an angle 

 proportionate to the extension of the spring piece and proportional 

 therefore to the pull on the test bar. The end of this pointer in 

 its motion always touches a piece of smoked glass, to which is given 

 a travel in its own plane proportional to the extension of the test 

 piece. In this way the diagram is drawn. After the test, the 

 glass is varnished to fix the black and the necessary particulars 

 about the test are written on it with a scriber. The glass is then 

 used as a negative and copies produced by photography. 



The thanks of the Society were conveyed to Prof. Warren for 

 his interesting and instructive exhibit. 



Nineteen members were present. 



Donations Received during the Month of June, 1887. 

 (The Names of the Donors are in Italics.) 

 TEANSACTIONS, JOUENALS, EEPOETS, &c. 

 Aberdeen — University Calendar for the year 1887-88. The University. 

 Amsterdam— Academie Eoyale des Sciences. Verslagen en 

 Mededeelingen, Afd. Natuurk. 3e Eeeks Deel IT., 

 Jaarboek 1885. The Academy. 



Berlin— Koniglich Preussische Akademie des Wissenschaften. 



Sitzungsberichte, No. 40, 22 Oct., 1885, and Nos. 40 

 to 53. 21 Oct. to 16 Dec, 1886. 

 Birmingham — Philosophical Society. Proceedings, Vol. IV., 



Part 2, Session 1884-85. The Society. 



Bremen— Naturwissenschaftlicher Verein. Abhandlungen, 



Band IX., Heft 4 (Schluss). 

 Brisbane — Eoyal Geographical Society of Australasia, 



(Queensland Branch). Proceedings and Trans. 



Vol. II., Part 2, 1886-7. 

 Brussels — Societe Eoyale Malacologique de Belgique. 



Proces-Verbal, Seance 7 Aout— 4 Decembre, 1886. ,, 



Calcutta — Geological Survey of India. Eecords, Vol. XX., 



Part 2, 1887. The Superintendent. 



•Cambridge ( Mass. ) — Museum of Comparative Zoology at 



Harvard College. Bulletin, Vol. XIII., No. 3, 



February, 1887. The Museum. 



Chapel Hill, N.C.— Elisha Mitchell Scientific Society. 



Journal 1885-1886. Third Year. The Society. 



Charlottesville, Va. — University of Virginia. Annals of 



Mathematics, Vol. III., No. 2, April, 1887. The University. 



Cincinnati — Cincinnati Society of Natural History. Journal, 



Vol. X., No. 1, April, 1887. The Society. 



