S64 



SURVEY OP THE COAST 



The micrometer microscope, in the foreo;oins; comparison, 

 was read hy addition, or from 78",7 onwards. On the I7th 

 of March, it was turned one half revolution horizontally, so 

 as to read l)y sul)traction, or from 78",8 backwards, to com- 

 pensate any possible influence of the micrometer. The mi- 

 crometer values were verified a»ain in this position, and 

 found as before ; all other thinst* beina; left as before, and 

 prepared for the comparison of the next day. 



On the 18th of March, early in the morning, all being ve- 

 rified again and found in good state, the comparisons were 

 repeated, with the results exhibited in the following table : — 



Micrometrio Corrected re- Meao 



Standaids readings suli- Mean nf tlie Cwreclionof suits to b' sub- Actual value ef of the 



contpured. trat-ttv^ from four results. microraeter. Iraut'-d f ■oin the distance, thcrrno- 



78",8. 78",8. meters. 



M'-+' 0" ,044075" 

 M,-|-, 0" ,043030 

 Ends chang. to mid. 

 M'+' 0",043250 

 Mo+i 0".043235_ 



>0",043900 0",0001756 0",043724 78",756276 



46 ,6 



W+y 0",03917.5"1 

 M.,+/; 0",039300 

 Ends chang. to mid. 

 M<:+ii 0',040'200 

 Mj+g 0",040135 



>0",039r02 0",0001588 0",039643 r8",760357 



48°,S 



M'+^ 0",041325" 

 M,+/f 0",()40830 

 Ends chang. to mid. 

 M'-J-." 0',041600 

 M,+« 0",041225. 



>0",041295 0",0001651 0",041130 78^758870 



The four double metre bars were now successively put 

 under comparison, in their four possible positions, the inver- 

 sion of the letters denoting the inversion of the bars : — 



