368 SURVEY OF THE COAST 



The following table will present these results : — 



Dat«ofcomp. M= M' M* M^ 



Mar. 15, AM. 39",380952064 39",S7992415 39",379854162 



Mar. 18, AM. 39",380964100 39",37970040 39",3840606 



Mar. 18, PM. 39",381151960 39",37953601 39".3836290 



Means 39",381022708 39",37972015 39",379854162 39",3838448 

 Correction of Brass Metre, as per Certificate +0" ,000393810 



Brass Metre corrected according to Certificate 39",380247972 



These results might now be compared with others: viz. 

 with those obtained by M. Pictet of Geneva, in 1802, and those 

 by Captain Kater, since mine were made ; but as 1 have not 

 the details of their operations and the expansion they used, on 

 which it is evident that much depends, I shall omit such 

 comparison here. 



I shall confine myself to inserting the final results found 

 by Mr. Troughton and myself, in London, in 18 1 3, from a 

 comparison of the two metres of Lenoir, in iron and brass, 

 with Mr. Troughton's own scale, each metre being compared 

 singly by the help of the butting pieces, as above described. 

 They are : — 



Temp, of Correction Value at 



Fahrenheit. (for tempi-rature.) 32". 



M'=39",3783658 45°,5 +0",0018848 39',3802506 



(for certificate.) 

 M*=39",3799395 46° ,0 +0",0003938 39",3803333 



the brass metre requiring no reduction for temperature. 



The mean of these two metres in this comparison may 

 be considered as identical with the mean of the three in the 

 comparison detiiled above ; and its difference from the mean 

 obtained above for the same metres is equal to 0,00030789. 



The consideration of all these results proves that all co- 

 pies of metres tend to be shorter than the original from 



