TRIANGULATION. 



169 



'^The base line of the triangulation of the twenty English miles to a point on the Colorado 

 from its junction with the Gila/' was measured by Lieut. N. Michler, corps topographical engi- 

 neers; with two iron rods, ^^A'' and ^^B/' corresponding with rod ^^B/' in the possession of 

 Mr. E. D, Cutts, U. S. Coast Survey, the length of which is 4.0002457 metres at 32^ Fahren- 

 heit. The length of one metre, at 32° Fahrenheit, is equal to 39.3685034 inches at G2^ Faliren- 

 heit of the standard made hy Troughton. 



Kate of expansion of rods for 1*^ Fahrenheit, .000006963535. 



The total length of the base, as computed by John O'Donoghue, computer, is 5,86Y feet 



5,9 inches. 



if rods^ at different temperatures ^ of 



Standard, 



Temperature 

 of iron rods. 



Length of rods at this 

 temperature, of Amer- 

 ican standard. 



Length of rods at this 

 lemperat'e,of the Eng- 

 lish imperial standard. 



62 



63 

 64 

 55 



56 

 57 

 58 

 59 

 60 

 61 



Inches. 



157.5056195 

 .5067161 

 .5078127 

 .5089093 

 .6100059 

 .5111025 

 .5121991 

 .5132957 

 .5143923 

 .5154889 



Inches* 

 157.512060 

 .513161 

 .614262 

 . 515363 

 .516464 

 .517565 

 .518666 

 ,519767 

 .620868 

 .521969 



Temperature 

 of iron rods. 



Length of rods at this Lenpth of rods at thit 



temperature, of Amer- 

 ican [Standard. 



icniperare, of the Knf- 

 lisb imperial standard* 



62 

 63 

 64 

 65 

 66 

 67 

 68 

 69 

 70 





■ 



Inches. 



157.5165555 

 .5176821 

 .6187787 

 .5198753 

 .6209719 

 . 5220685 

 .6231651 

 .5242617 

 .5253583 





Inches. 



157.523070 



.524171 

 .625272 



,620373 

 .627474 



.528575 



.520676 



.630777 



. 631878 



from the length of the meastiring-7'od at the different 



vations. 



Angle of eleva- 

 tion. 



Sura to be subtracted 

 from the length of the 

 rod. 



00 



05 

 10 

 15 

 20 

 25 

 30 



Inches. 

 0.0000000 



0, 0001733 

 0.0006615 



0.0014964 

 0.0026612 

 0.0041585 



0. 0061275 



Angle of eleva- 



tions. 



O 



i 







.S5 







40 







45 







50 







55 



1 



00 



Sum to be subtracted 

 from the length of the 

 rod. 



Inches. 



0. 0081595 

 0.0106641 



0.0134995 

 0.0166656 

 0.0201626 

 0- 0239903 



V 



The point "F" was Lieut. MicUer's observatory, and distant from the junction of the Colo- 

 rado and Gila, in a straight line, 104024.34 feet; the azimuth of this line, at the point "F'/' 



N. E. and its len-th is 1575.66 feet short of twenty miles. (See results of calcu- 



is 36° 14' 10" 



The latitude of point -F," as obtained from triangulation, is 32° 29' 42".64 N., and longi- 

 tude 114° 48' 09".51 west of Greenwich. The latitude used, however, is that obtained from 

 observations with zenith telescope, and is 32° 29' 41".65 N.; but the longitude taken is that 

 obtained by triangulation. --.it r 



The initial point, in the middle of the Colorado, was determined by prolonging the line from 

 the junction, passing through -F" 1575.66 feet, measured with the ^ " 



two iron rods, "A" and 



Vol. I 



22 



