188G.] NEW YORK ACADEMY OF SCIENCES. J 53 



February 8, 188G. 



Stated Meeting. 



Tlie President, Du. J. S. Newberry, in the Chair. 



A hirge audience present in the east lecture room of the Li- 

 brary Building, Columbia College. 



The third lecture of the Popular Lecture Course was deliv- 

 ered by Dr. John S. Billings. 



Subject : the uses and dangers of micro-organisms. 



{Illustrated by the cultivated organisms, charts and lantern- 

 views.) 



February 15, 1886. 



Stated Meeting. 

 The President, Dr. J. S. Newberry, in the chair. 

 Twenty-five persons present. 

 Prof. John K. Rees read the following papers: 



I. A new electric winding-apparatus por clocks. 



Accurate time is necessary for most of the scientific work of 

 the observatory. By star observations the error of a clock can 

 be determined to within about one-fiftieth of a second; but 

 during cloudy weather observations cannot be made, and then 

 the clock error must be determined by adding to the error at a 

 known date the accumulation of error due to the clock^s rate. 

 If this rate is constant and can be depended upon, such an error 

 will be an accurately determined one; but if the clock's rate is 

 not constant, such an error may be far from the truth. It is im- 

 portant, therefore, that the observatory should have a clock con- 

 structed in such a way as to make its rate constant or very nearly 

 so. It was long thought that the practical solution of the problem 

 of the construction of a clock of constant rate would be found in the 

 adoption of a pendulum which would not alter its length with the 

 temperature, and so we find Graham, Harrison and others de- 

 vising forms of compensated pendulums in which the downward 

 expansion due to heat, increasing the length of the pendulum, 

 was counteracted by an equal upward expansion, shortening the 



