OF ARTS AND SCIENCES. 



335 



usually about 0°.4 C, will have become absorbed in the general tem- 

 perature of the room, and the several bars will have reached a state of 

 rest as far as this special increase is concerned. 



We are now prepared to enter upon an examination of the standard 

 prototypes described in this paper. The various comparidons will be 

 given nearly in the order in which they were made. 



Comparison of Yard R^"" with "Bronze 11" at Washington. 



Professor Hilgard having kindly consented to undertake the com- 

 parison of the bronze yard R^^ with "Bronze 11," Assistant Edwin 

 Smith was assigned to this work. The observations by Mr. Smith 

 were made with the Lane vertical comparator. At his request, the 

 writer made independent micrometer readings, after all the adjustments 

 had been made, but there was a complete avoidance of any knowledge 

 of the results obtained. 



The fidl text of Professor Hilgard's report will be found in the 

 report by the writer to the Pratt and Whitney Company, relative to the 

 standards constructed for them ; but the portion relating to R.^ is given 

 here. 



At 54°.70 F. " Bronze 11 " — i?^ = —0.000052 inch. 

 T— « Bronze 11" = +0.000088 " 



R„ 



~ +0.000036 



