PHILOSOPHICAL SOCIETY OP WASHINGTON. 53 



At the conclusion of the reading the Society adjourned at 

 9.15 P. M. for the purpose of conversation and social intercourse. 



ITOth Meeting. December 6, 1879. 



Vice-President William B. Taylor in the Chair. 

 Twenty-four members present. 

 The minutes of the last meeting were read and adopted. 



The Chair stated to the Society that Mr. E. S. Holden, who 

 had been elected at the meeting of Noyember 8th to fill one of 

 the Secretaryships of the Society, had been compelled to decline 

 the position on account of the requirements of his professional 

 duties, and called upon the Secretary, Theodore Gill, to read 

 Mr. Holden's letter of declination. This letter will be found 

 upon the records of the proceedings of the General Committee of 

 the Society. 



The Chair then announced that, conformably to the provisions 

 of the Constitution of the Society, the General Committee had 

 elected Mr. C. E. Button to fill the position of Secretary in the 

 place of Mr. Holden, declined. 



The order of exercises for the evening was announced. 



1. Mr. J. J. Woodward — Some Apparatus recently brought 

 into use by the Medical Department of the Army for the Exami- 

 nation of the Eye. 



2. Mr. Marcus Baker — Discussion of a Geometric Problem, 

 with several solutions. 



Dr. WooDW^ARD then explained to the Society the origin of the 

 rules recently introduced into the Medical Department of the 

 Army for the examination and testing of the powers of vision in 

 recruits. The object of these rules was to obtain sufficiently ac- 

 curate tests of those powers which enable the examining surgeon 

 to discriminate between defects which would render a soldier 

 unfit for the requirements of the military service and those which 

 were insufficiently serious to cause his rejection. 



The apparatus employed consisted first of a pack of test cards 

 with circular spots on them four-tenths of an inch in diameter 

 48 



