TRIGONOMETRICAL OPERATIONS, &C. 2^1 



. ticulars of that arc will appear before the public in 

 another place, it will be sufficient barely to mention 

 it here, as being the scale from which the latitudes 

 of places are computed.* 



A full account of this survey being intended for a 

 separate publication at some future period, when 

 more materials wiil be collected, I have chosen for 

 the subject of the present paper, that part of it which 

 I think will be the most interesting; viz. the trian- 

 gular operations in ccnnecting the two seas, and the 

 method by which the difference of longitude has 

 been determined in my progress from east to west : 

 and that it may be better adapted to the general 

 reader, who, perhaps, may have neither time nor in- 

 clination to enter into minute detail, I shall previ- 

 ously state, in a concise form, the manner in which 

 these extensive operations have been carried over the 

 great mountains, forming the eastern and western 



* It may not be amiss to mention here, that some little irre;.'ularity 

 had occurred at some of the stations of observation, occasioned no 

 doubt by the plumb-line's being drawn out of its vertical position ; but 

 it is impossible to say at which of the stations this has happened, as at 

 the three where the zenith distances were deemed the most unexcepti- 

 onable, there is nothing, to appearance, which can be considered com- 

 petent to produce the efl'ect in question. One of these tiiree is in the 

 ceded districts, in latitude 14° and upwards. Another one is on the 

 table land, near Bangalore, in lat. 18°, and tlie most southerly one is 

 in the Coimbetoor country, in lat. 11°. The arc, comprised between 

 the stations in 1 i° and 13°, gives the measure of the decree 60530 

 fathoms; and that, comprehended between 11° and 14°, gives only 

 604^1 fathoms ; so that there evidently has existed some cause, for 

 deflecting the plumb-line, at one or both of these northern stations. 

 I have, for the present, taken the mean result of the two cases, re- 

 ducing them to the ^ime latitude, 1 1" 59' 55", which is 60494 fa- 

 thoms. This measure, used with all the recent measurement;* made in 

 England, France, and at the polar circle, will give the mean elliplicity 

 of the earth ^i^ nearly, and therefore the polar, to the equatorial dia- 

 meter, will be in the ratio of 1 to 1.003125 nearly. 



U2 



