I48 ASTRONOMICAL OBSERVATIONS 



The altitudes were taken by means of the image 

 in quicksilver, which, if the sun was the object, was 

 defended from the wind by a covering of thin gauze, 

 as recommended by Mr. Burrow in the first volume 

 of the Asiatic Researches. When the altitude of a 

 star was to be taken, this method did not answer, as 

 it rendered the image too obscure. A thick cloth 

 was therefore properly disposed to windward of the 

 mercury. 



The small telescope belonging to the sextant was 

 used in all the observations. 



As the instrument is only graduated to J25 de- 

 grees, I could not take altitudes exceeding 62 de- 

 crees. White the sun's meridian altitude could be 

 observed, I have preferred it for the latitude; but, 

 as this was soon about to be impracticable, I began, 

 on the 29th of February, to compare the latitudes by 

 meridian altitude, with those obtained from two al- 

 titudes and the elapsed time, by the rule in the re- 

 quisite tables, in order to judge how far the latter 

 might be depended on. The result of the compari- 

 son, which appears in the observations from that 

 time to the 15th of March, determined me to trust 

 to those double altitudes, while they could be taken 

 within the prescribed limits ; at the same time, com- 

 paring them occasionally with observations by a 

 fixed star. From the first of April, 1 was obliged 

 to trust entirely to the stars ; and, to make the ob- 

 servations by them as accurate as possible, I have, 

 when circumstances would allow, taken the meridian 

 altitude of one to the north, and another to the 



south, 



