OF THE UNITED STATES. 



'27 i 



toises are downwards, the erect positions that they are up- 

 wards. 



The length of tiic contact in the toise of Canivet is about 

 two-thirds of an inch. In this three points were observed, 

 as marked Plate IX. fig. 8, between mm, in the middle ; 

 between ii, at about one-fourth of the coritact with the ma- 

 trix from the inner corner ; and between ee, about 0",06 

 from the end of the contact. The toise was of course kept 

 with the matrix, as this formed a proper butting piece to 

 observe by, though the line was not altogether as sharp as 

 that with tlie butting pieces made for the other standards. 

 The breadtli of the matrix prevented me however from turn- 

 ing it end for end, as tliere was not room enough between 

 the microscopes and their supports. 



The following table will present these comparisons ; — 



CorreclcJ 

 readings. 



A'aluc of llie Tem- 

 scalc or pera- 



measurc. tare. 



33°,4 



Toises Mici-omrter Mean Correction 



com- readings sub- of ihe read- of 



pared, tinctire from ings. raicroractcr. 



76",8(Xn375 



C" 0',058250 "^ 



C O",059J00 



C« 0",056400 



Chan, end for end ^0",0576958 (K,OOOS058 0",0573900 76".742r475 



u^ ,057050 



,3 0,058675 



,0 0",056300 



L 0",061530 ■) 35M 



1 0, 0605 50 

 Chan, end for end W',0G06200 0',0003i!13 0",0592987 76,7408389 

 I. 0,060700 

 q a,059700 J 36° ,9 



'' ^''^cl^?^ I 0",0618350 0",0005277 0",06l50-3 76',7386302 

 ,; ,0d2oo0 ) 



'". ^'^-?^^!! ? 0,0536750 O',0002845 0,0533905 76',7467470 



39' ,0 



The results of this table are now to be reduced to the 

 standard temperature of 3;^'' Fahrenheit, as was done for the 



