AMERICAN ASSOCIA TION FOR THE AD VANCEMENT OF SCIENCE. 289 



Results of observation and experiment with an " Almacantar " of four inches 

 aperture, at the Harvard College, S. C. Chandler, Jr. On the colors of variable 

 stars, S. C, Chandler, Jr. Colors of the stars, E. C. Pickering. Temporary 

 stars, Daniel Kirkwood. A criterion for the rejection of doubtful observations, 

 Mansfield Merriman. On the magnitude of the errors which may be introduced 

 in the reduction of an observed system of stellar co-ordinates to an assumed nor- 

 mal system by graphic methods, William A. Rogers. Systematic errors in stellar 

 magnitudes, E. 'C. Pickering. The average asteroid orbit and the asteroid ring, 

 M. W. Harrington. On the original graduation of the Harvard College meridian 

 circle, in situ, William A. Rogers and George A. Clark. To exhibit and describe 

 a model of the ruled cubic surface known as the cylindroid, Robert S. Ball. The 

 geodetic work of the United States Coast and Geodetic Survey, J. Howard Gore. 

 The lunar aurora, John Haywood. Micrometric observations of Jupiter's third 

 satellite, David P. Todd. On the course of the corrections to the heliocentric 

 longitudes of Newcomb's tables of Uranus and Neptune, David P. Todd. Me- 

 chanical arithmetic illustrated by the averaging machine, W. S. Auchincloss. 

 Analysis of the formula for the Moon's latitude as effected by the figure of the 

 Earth, John N. Stockwell. The products of vectors, Samuel Emerson. On an 



d, I d\ t^ I d\ t^' 



indirect solution of the equation a = ac -] 1 1 — 3 ac. to the sixth 



d^ dt 2 dt' 2 d,.3 



power of the time, in which — is a function of four variables, William A. Rogers. 



dt 

 Description of the Leander McCormick observatory of the University of Virginia, 

 Ormond Stone. On the visibility of faint objects under red illumination, G. W. 

 Hough. A brief account of some preliminary experiments in the construction 

 of clocks of precision, Leonard Waldo. A collection of formula for the area of 

 a plane triangle, Marcus Baker. The nebulae, Lewis Swift. On the fundamental 

 formula of statistical mechanics, with applications to astronomy and thermo-dyna- 

 mics, J. Willard Gibbs. On the rotation of a rigid system in four- dimensional 

 space, Irving Stringham. A geometrical interpretation of the Hnear bi-lateral 

 quaternion equation, Irving Stringham. A new apparatus for the study of Bayle's 

 law, Leroy C. Cooley. On the mean temperature of the two hemispheres of the 

 earth, H. Hennessy. On the constitution of the earth and planets, H. 

 Hennessy. On an international standard for measurements, H. Hennessy. 

 Linear functions of points, lines and planes, E. W. Hyde. Late researches 

 on the solar surface with special reference to evanescent spots, S. I. Perry. Har- 

 monic motion in stellar systems, Pliny Earle Chase. 



Section B (Physics) assembled in the chapel of the Episcopal Academy. 

 John Trowbridge, of Cambridge, Mass., acted as chairman and N. D. C. Hodges, 

 of Salem, Mass., as secretary. The papers presented were: 



On the Fritts' selenium cells and batteries, Charles E. Fritts. Relation of 

 the electromotive force of a Daniell cell and the strength of the zinc sulphate 

 solution, H. S. Carhart. Note on the periodic modification of electrostatic in- 



