Use of the Zenith Telescope in Determining Latitudes. 199 
NUMBER IIL 
Pairs Selected for Observation. 
See . 
bay Star. laPs.| Mag. [Auth. AR. NPD. | AEA) ZZ] Bp. 
Ra | 4 Hes ig Fg APPR SEs nt 
6109 | N ‘VI 3 [17 55 39144 29 23) ga° 1° 46! 
Time wl Sagittarii at 118 of 46 
: 6203 | S | VI | 1 |18 10 59/47 53 21/22! 44} —6 16 | 1° 38 
e @ Lyre .. 0, 1 31 51 
Time <{6599..28:... {19 Ir o 
6 Aquile.... {19 17 5 
§ 6681 | N Vig 3 j19 23 04/32 16 29 ee 13 59 
&s, 6740} S }1V | 3. |19. 33, 27/60 11 24 ate 107 113 56 
6771 | S 4-V 3 |19 38 53/53 ‘00 19 6 45 
3} Ss INT v dS ip: 2SBG9 <3 S079 1A 39:16: 5 
6937; S | V 3 j20 03 51/53 35 56 7 20 
. : 6959 | N| V 1 |20 08 22/38 59 1 35 08 | +6 08 7 16 
5 § 7oor|.S | VI ¥ 190 2130097, 27 © 51 o; 1 
{ 7062 | N | V4 | 2 [20 22 27/41 06 48 387 95) 7 39115 
« 
6 § 7398 | S FIV4| 4 [or 1s 31/51 13 58] . 2 4 5 
{ IN vr | i jay 9G 18)4x 09 995, ar 23 7 37 5 08 
}_Time 8 Aquarii......|2r_23_3 ath, 
_ From the table No. II, the pairs which best fulfill the condi- 
tions heretofore stated, are selected, and the difference between 
twice the co-latitude of the place and the sum of polar distances, 
18 entered with its proper sign, (130°—2L—( AntAs ) this 
quantity being equal to the difference of the zenith distances of the 
two stars composing the pair, (since 180°-2L= A. + A.t+Zn-4s, 
L being the latitude A,, and A, the polar distances of the star 
N, and 8. of the zenith respectively, and Z, and Z, the zenith 
distances of the same star.) ; 
_ The object of obtaining the zenith distances approximately, 
8, So to select the pairs that the sum of all their differences, with 
their proper signs, shall be nearly zero; which, as before stated, 
corrects for any error in the determinations of the micrometer 
values which are used in the observations. 
