﻿320 ON EXTENDING A GEOGRAPHICAL SURVEY 



ment has been pleased to authorise me to send for. 

 At present it seemed most desirable that I should 

 begin in Mysore, and endeavour to forward the sur- 

 veys of that country. Having made a rirst measure- 

 ment there, I think, with the instruments I at pre- 

 sent possess, it will be best not to extend my opera- 

 tions too far from some assumed meridian, as 1 can 

 de{3end more upon meridional celestial arcs than upon 

 any computed oblique ones. The instrument I have 

 for taking zenitli distances is a zenith sector of five 

 feet radius, made by Mr. Ramsden, with a micro- 

 meter scale that defines nearly one-tenth of a second. 

 Witli this I can determine two parallels of latitude to 

 he depended on between which to compute by ter- 

 restrial measure the relative situations of intermediate 

 places as to latitude. Tlie instrument with which I 

 take horizontal angles is a circular transit instrument, 

 piade by Mr. Troughton, whose horizontal limb 

 is only eight inches radius, without a micrometer, 

 but Mdiich is graduated to 10"; and though it is an 

 excellent instrument, correct and easy in its adjust- 

 ments, yet its powers are not sufficient for taking 

 horizontal angles where they are to be reduced to thq 

 iangles made by the chords. 



SECTION J. 



Containing an Account of the Measinr.mcnt of a Base 

 Line on the Table Land of the Mr so re Country 

 near Bax galore. 



I MENT I ON Ki) above my reasons for making a 

 xncasurement in the Mysore country. This measure- 

 ment may, however, not be thougiit so satisfactory 

 as if it hud been done near the sea coast, on account 



of 



