Survey of Northeast Greenland. 287 
Controlling computation by the zenith distance. 
ZR ee 77°41'.6 
Di... 29) 
Obie olor ial 
Dae 1792586 
5-1 89-593 logsec.... 3.69118 
ds В Wr Sh — cos.... 9.98992 
ose. 6 30.0 — sin .... 9.05386 
o— 0. 71 11.6 — созес.. 0.02383 
2.75879 
log tan !/za 1.37940 
Control: а = + 175°13' = + 184947" 
A control of this kind showing a difference of 50’ from the value 
to be controlled is of course quite unsatisfactory, but it is a question 
whether one could expect a much better one, because the azimuth 
so near the meridian varies rapidly, whereas the zenith distance 
varies comparatively very slowly. 
A test of the significance of the control is most easily undertaken 
by examining the value of 4z, when Да is put equal to 50’, or which 
by approximation comes to the same thing, when J? is put equal 
to 3™. For this purpose one may use the formule of the reduction 
to the meridian in the term 
ф = 180° + å— 2 Ат + A? cot (ф + д)п (lower culmination), 
2sin?!let 2 sin? 15 t 
retenue 
The last term of the formula, A*cot(o + 9)n, can here be left 
out as being of no importance. 
As the hour angle corresponding to the mean of the clock times 
of the two pointings is 12516™22s, the two values of t, for which the 
reduction Am is to be computed, may conveniently be put at 
В — 120 PET ES PESTE 
ф = 83°29".3;100— 1847 .7 
where А = cos w cos д cosec (d + ¢), m = 
05 COS ER 2... 9.0546 
——'— À nee 9.9762 
— cosec (9 +g).. 0.0101 
— A ee 9.0409 .... 9.0409 
— к 2.6451 .... 2.8034 
AA RTE 1.6860 1.8443 
Au MO 48.5 69”.9 
42 1699455 — С OA: 
1) log т is taken from table 29 in: TH. ALBRECHT, Formeln und НЫ (а ет für 
geographische Ortsbestimmungen, 3. Auflage, Leipzig 1894. 
XLVI. 19 
