70 H. G. Fourcade.—On the [April 26, 
eee | 
Mean of Vernier Readings. Resulting Angle. 
Number 
of creme aN pra ot tee Ol Pe ene ere 
repetitions; Origin 0° Origin 180° Origin 0° Origin 180° 
° / iT] / / oy W ] 7] 
0 359 50 0 30 9 
1 131 53 10 52 50 biets ‘isin 
10 240 18 O 19 30 132 2 48°0 2 59:0 
1] 12 20 15 23 10 2 45°0 3 0:9 
12 144 23 20 25 50 2 46°7 2 a9 
13 276 25 45 298 to) 2 45°0 2 59°5 
14 48 28 15 32 25 2 43°9 a 18 
15 180 31 35 35 «5 2 46°3 3 O03 
16 312 34 10 38 30 2 45°6 ‘a eres ( 
17 84 36 45 41 15 2 450 3 09 
18 216 39 50 44 30 2 46°1 a Wea 
19 348 41 55 47 35 2 43°9 Taree be, 
20 120 44 55 50 40 2 44-7 3 
21 252 48 O 53 20 DAG, 3. TO 
The instrumental errors of the 6-inch Everest theodolite used in 
the measurement were determined by obvious methods ; the inclination 
of the horizontal axis relatively to the upper vertical axis was found 
to be 50°"0 (right hand pivot highest) and that between the upper 
and lower vertical axes 4’ 26" in the direction of division 93 (so that 
A = 273°.) The collimation was adjusted accurately enough to 
render its effect upon the observed angles practically insensible. 
The calculation of the corrections from these data, by the formulae 
above, gave the results shown in this table : 
~ 
