. proceedings: philosophical society 137 



communicate to the General Committee that it is the sense of the 

 meeting that the membership hst be revised, pubhshed, and distributed 

 more frequently. It was moved and carried that the plan of having 

 refreshments at the regular meetings be presented to the General 

 Committee for consideration. There was also informal discussion as 

 to the desirability of a revision of the by-laws and organization. It 

 was suggested that the General Committee empower the Executive 

 Committee to designate other meeting places than the Cosmos Club 

 when desired, and that the General Committee provide for taking of 

 votes by post when specific questions arise requiring prompt action. 



The 749th meeting was held on January 2, 1915, at the Cosmos Club, 

 President Eichelberger in the chair; 20 persons present. 



Mr. F. E. Wright spoke on The measurement of relative strain in 

 glass. The history" of researches with reference to the optical effects 

 resulting from strain in glass and to the methods suggested for meas- 

 uring such effects was reviewed. In the method used by the speaker, 

 the glass plate is examined in strong monochromatic light between 

 crossed nicols. The path difference of the emergent light waves at 

 any given point is measured by a bi-quartz compensator of special 

 type. The conversion of the optical retardations thus measured to the 

 corresponding elastic deformation data is accomplished by direct meas- 

 urements in the glass subjected to a series of mechanical loads of known 

 magnitudes. The paper was illustrated by experiments and projections 

 on the screen. The discussion was participated in by Messrs. Bauer. 

 White, C. A. Briggs, Marvin, Curtis and Sosman particular 

 inquiry being made with reference to applications in determining strains 

 in engineering constructions. 



Mr. M. D. Hersey presented a paper on Some characteristics of 

 aneroid harometers. The speaker described briefly the general prin- 

 ciples and mechanical details of the aneroid barometer. The various, 

 types were illustrated by lantern slides and sketches. In the consid- 

 eration of relative merits and permissible limits of error account must 

 be taken of the proposed use. The different classes of error were dis- 

 cussed. The chief source of error appears to be in the construction of 

 the vacuum box. Mr. JMarvin discussed the paper, stating that his 

 experience confirmed the conclusion of the speaker and that undoubt- 

 edly the greatest improvement must be looked for in better material 

 for the vacuum box. 



The 750th meeting was held on January 16, 1915, at the Cosmos 

 Club, President Eichelberger in the chair; 50 persons present. 



The evening was devoted to the a'ddress of the retiring President, 

 Mr. L. A. Fischer, on Measurement of length. The speaker briefly 

 sketched the early history of the English yard and the origin of the 

 present metric standards of length. The earliest authentic copies 

 of both the yard and the meter "in the United States were brought 

 to this country by Ferdinand Hassler, the first superintendent of the 

 Coast Survey, and when he organized that service later on the meter 



