520 
PHILOSOPHICAL SOCIETY OF WASHINGTON. 
Mr. T. C. Mendenhall made a communication on The use 
of planes and knife-edges in pendulums. [Published in the 
American Journal of Science. 8°, New Haven, 1893, Feb., 3d 
series, vol. 45, no. 266, pp. 144-150.] 
This was discussed by Messrs. Harkness, Paul, Chapman, 
Farquhar, and Preston. 
Mr. R. S. Woodward made a communication entitled The use 
of long steel tapes for measuring base lines. [Published in U. S. 
Coast and Geodetic Survey Report for 1892. 8°, Washington, 
1893, part 2, Appendix 8, pp. 334-503.] 
Owing to the lateness of the hour, discussion of this paper was 
postponed till the next meeting. 
399th Meeting. February 4, 1893. 
President Goode in the chair. 
Thirty-eight members present. 
Mr. R. S. Woodward read an abstract of his paper presented 
at the last meeting, and the paper was then discussed by Messrs. 
Paul, Dall, Farquhar, Harkness, Abbe, Mendenhall, and 
Woodward. 
Mr. F. L. 0. Wadsworth made a communication entitled 
Method of determination of the metre in terms of a wave length 
of light. [It consisted of an abstract of a special report by A. A. 
Michelson, entitled Determination experimental de la valeur 
du metre en longueurs d’ondes lumineuses, which was published 
in Travaux et memoires du Bureau Internationale des Poids et 
Mesures, 1894, vol. 11.] 
It was discussed by Messrs. Mendenhall, Harkness, Paul, 
and Wadsworth. 
400th Meeting (Special). February 18, 1893. 
The program for this meeting was a special one designed to 
suitably commemorate the four hundredth meeting of the Society. 
For its proceedings see pp. 547-562. 
