﻿S3Q ON EXTENDING A GEOGRAPHICAL SURVET 



telescope of the circular instrument was directed to 

 the flag staff. — It was intended to determine this 

 angle, by having a blue light at the opposite end 

 of the base, at the time tliat the star was at its 

 greatest elongation ; but, unfortunately, the weather 

 became so unfavourable, that the star never made 

 its appearance, for upwards of a fortnight — and as I 

 was ready to move during all that time, I therefore 

 determined to remain no longer at that station, but 

 wait the event of more settled weather, M'hich pro- 

 bably would happen before I had extended my ope- 

 rations very far, either to the eastward or westward 

 of Bangalore. I therefore prepared to take angles 

 at the most suitable places, and proceed to lay down 

 the positions of the principal oljjects within the vici^ 

 nity of Bangalore. 



The latitude of the South end of the base M'as 

 obtained some time after, by o!)serving, at a station 

 ^OYih Oi Bangalore, which, with tlie two extremi- 

 ties of the base, formed a triangle. Those observa- 

 tions were made v/ith tl^.e zenith sector on the 19th, 

 20th, and 21st of Janr.ary, by taking the zenith dis- 

 tance of the star Aldebaran, whose declination Avas 



corrected 



chain (whose length is JOG feet at t^ of temperature) extends when the 

 thermoineter is at a^.— Then the formula for the different cases willlji^ 



1 S= 



IOO + 



n— 1° X ,00763— (s — t)" X ,0x237 



2 K— 100 + 



f 



t— s'' X ,ci 237— (t—n)' X ,00763 



S=z 



ift. 1004- 



n — s" X, 00763 -|"t — s*x, 01 237 — ,00763 



y% — n*" X, 06763 +s — t** X ,01237 — >oo763 



3(1.100 — ( 



763 \ 



► Feet, 



If the chain should measure -}-or — any quantity (q) at the tempera- 

 tare t*5 from wear Sec, then put iQO + q in place of lOO in each 

 equation. 



