58 ASTRONOMICAL OBSERVATIONS 



place, behind which I could place a light to adjuft with 

 by night. There was another object alfo to the fouth, 

 about 1500 yards off, which I could ufe by day; and 

 both thefe were fixed when the tranfits by telefcope 

 and equal altitudes agreed, and were examined from 

 time to time. 



I had only a tolerably good Hadley's quadrant and 

 quickfilver, till December, 1776, when I was lucky 

 enough to get an 18 inch land quadrant, made by 

 Ramsden, with a micrometer to fubdivide the nonius. 

 This inverts, and is capable of the niceft adjuftments. 

 My firft telefcope was an 18 inch reflector, made by 

 Gregory. 



In Auguft, 1777, I obtained Mr. Smith's refractor, 

 made by Dollond, with a triple object glafs, and a 

 double object glafs micrometer. And I made a polar 

 axis for it of brafs with rack-work, and a declination 

 circle not divided, which is alfo racked; to which, when 

 the micrometer was ufed, the telefcope was fixed. 



I likewife communicate obfervations made by rny- 

 felf chiefly, and by Lieutenant Colebrooke for me, 

 to afcertain the longitudes and latitudes of places be- 

 tween Madras and Calcutta, 



Going to Madras in 1782, I ufed a Hadley's o&ant 

 and quickfilver, which I fhall here defcribe. 



The octant had a wooden index. I feparated the part 

 which carries the fpeculum from the arm ; then fixed it 

 , into a lath, and turned it on its own center : it was 

 three tenths of an inch thick; the thicknefs was divided 

 into three parts, and then the edge was turned away on 

 each fide ; fo that the whole piece of wood became like 

 ;hree wheels of different diameters joined together on 

 % their 



