298 



PROCEEDINGS OF THE AMERICAN ACADEMY 



DIMENSIONS. 



WIDTH OF DEFINING LINES. 



The discussion of these prototypes will proceed in the fullowing 

 order : — 



(a) Description of comparators. 



(b) Description of comparing-rooms. 



(c) Discussion of thermometers. 



(d) Description of microscopes. Values of the micrometer screws. 



(e) Investigation of the time required for a given change of tempera- 



ture to produce its normal effect u^ion bars having different 

 masses. 



