Survey of Northeast Greenland. 303 
readings at the station and at the surface of the sea. This demand 
one can, as a rule, not satisfy, but one must be content to read off 
one's barometer at the level of the'sea before the ascent and after 
the descent, as well as at the station after the ascent and before the 
descent, as indicated in the example on p. 297. In order to make 
sure against the effect of disturbances in the instrument during the 
ascent it answers the purpose to use three aneroids. 
Examples of the computations will be found in the above-men- 
tioned work of Monn’s. As to the example given on р. 297 a com- 
putation corresponding to the accuracy of the observation may be 
performed in the following manner: 
Åscent. 
2: 1146.5 table У \ 8007.9 21750.0 table V \ 80451 *\748.0 table \ 8023,8 
approximate difk.ofaltitudeng. 1594 ...,..,,......... ОО ES ET SELER SEES SEE 155.0 
N U0 2.1...) pag’ UN BRÆT, +10 
dt НИЙ О tn REE en Er N en coe 156.0 
Descent. 
ь 1159.2 Moun (81422 , {762.8 Moun 481799 , f 760.3 Moun { 8153.8 
117436 table V U7976.9 ?\746.1 table V \80036  ° (744.11 table V (7982.3 
approximate diff. ofaltitudeh,.. 165.3 :.......:,...,,::1 И ART neg ee ae 171.5 
temp. corr. 2(+ 1.8-+-0.6) 708. +08 .................. UNE ee IE +08 
diff. of altitude............ п ee ne. re 170.7 
Mean of the-six, detferminations-. "ee. 165.5 
Altitude ofthe camping site above the level ofthesea 2.0 
Altitude of telescope... 167.5 
When the barometric measuring is performed as here mentioned, 
it is in itself not very satisfactory, and gives a greater uncertainty 
in the distance measured than is desirable. Therefore one also ought 
to have one’s attention directed towards every possibility of improving 
or at any rate controlling the result. This may, for instance, be done 
by means of trigonometric levelling at a point, the altitude and 
distance of which from the station are known. An example of such 
a particularly successful control is given on p. 299 in levelling from 
Station K III to Station KI. In the section on terrestrial refraction 
certain practical hints are given as to the way in which one may, 
by means of certain meteorological and topographical conditions, 
form an estimate of the value of a control of this kind. Here I shall 
only remark that when the distance, at which the levelling takes 
place, exceeds 30km, the control often becomes rather valueless, 
owing to the uncertainty of the refraction. 
XLVI. 20 
1761.6 Moun f 8167.3 f 765.8 Монк f 8211.1 [762.6 Moun f 8177.8 
