Geodesy : the eastern oblique arc of the United States and osculating spheroid / by ChasASchott . ures ofhorizontal angles by Stiperintendent Hassler date from1833 and were made with a 60 theodolite, first em-ployed at station Weasel in 1817. Subsequently heused the 75 theodolite, first employed at station WestHills in 1836. This last instrument was in continu-oustise till November, 1S73, when it met with an acci-dent at station Sawaiee, Georgia. It was struck Ina tornado and, notwithstanding its weight of 300pounds, was hurled from its .stand and irrejxnabh-damaged. In consequence of the work
Geodesy : the eastern oblique arc of the United States and osculating spheroid / by ChasASchott . ures ofhorizontal angles by Stiperintendent Hassler date from1833 and were made with a 60 theodolite, first em-ployed at station Weasel in 1817. Subsequently heused the 75 theodolite, first employed at station WestHills in 1836. This last instrument was in continu-oustise till November, 1S73, when it met with an acci-dent at station Sawaiee, Georgia. It was struck Ina tornado and, notwithstanding its weight of 300pounds, was hurled from its .stand and irrejxnabh-damaged. In consequence of the work added between 1862 and 1865, and the reoccupation ofthree of the old stations, a new adjustment of the base net became uecessar\. Weights hadto be introduced in consequence of the unequal values of the resulting tirections due tothe relatively small number of series in the older work. It was dttue by the same methodas already explained in connction with the adjustment of the Epping base net. From the closing of 17 triangles we haw the mean error of a triangle ./ ~ ^ ^ ± oS4 antl of Sandford. 10 O 10 20 Statute Miles an angle 0-84 049, . =^ zfc o4g and theprol)able error of a direction o074 \ —y^V 3 ?v^- The approximate average probable error of a (.lnecti(.)n from station adjustment result-ing from 36 directions is e^= ztoH). hence the square of the triangle combination *l)fnveil from siiirit levels. 48 THE EAvSTERN OBLIQUE ARC. error r equals (o23)^—(olg) or f, = ± oi3, that is, the combination error is butshghtlv less than the observing error e^^. If t\ is added to each value of = i/{e\-\-eJ. Among the values of e^ there was oneexceptionally large, and, omitting it, we find t^ = ± oi8, hence e^ =V(o233)°—(olSs)= =b oi44and/i = 1/[( oi44)+(,,] . and in order to make the average sum of the recip-rocals of the weights nearly unity, the values of i/p were multiplied by 13. The rangein these relative weights is still -large, the ratio of the greatest to the least being
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