Proceedings of the Albany Institute. 297 



He gave a general discussion and exposition of the 

 subject, reviewing the ground of a previous lecture before 

 the Institute. In that lecture he had alluded to the method 

 of testing personal equation in use at the Dudley Observa- 

 tory, by means of the chronograph. At this time he had the 

 instrument in the room, explained its working to the 

 members, and tested its operation, by taking the personal 

 equations of those present. 



The apparatus consists of a circular disk, divided by 

 radial lines into equal angular spaces. On the under edge 

 of the disk are placed large pins at equal intervals. The 

 disk being made to revolve at a uniform rate, by means of 

 simple clock work, and the observer looking towards it 

 from across the room through a small telescope, would see 

 these pins pass at equal intervals of time, across his line 

 of sight. The instant of the passage is marked by the 

 observer's completing the circuit of an electric current 

 by simple pressure of the hand on a small magnet, 

 thus causing a mark to be made upon a sheet of paper 

 stretched upon the disk, in the same way as marks are 

 made in an ordinary telegraphic instrument. The distance 

 of the mark behind the line passing through the pin 

 determine the equation of the observer. 



Dr. Hough stated that a member was desirous of pur- 

 chasing a copy of the Transations published by the Institute. 

 On motion, the request was referred to Mr. Munsell and 

 the treasurer with authority. 



The following nominations for membership were made : 

 By Paul F. Cooper, Mr. Leonard Kip ; and by Dr. Mosher, 

 Peter Hogan, both as resident members ; by Gen. Read, Mr. 

 Horatio Gates Jones, secretary of the Pennsylvania Histori- 

 cal Society, and Rev. Leighton Coleman, Wilmington, Del., 

 as corresponding members ; by Dr. Hough, Mr. Henry B. 

 Dawson, of Morrisania, as corresponding member; by 



[Trans. vi.~\ 37* 



