IN FORT WILLIAM, &C. Jt 



I believe the watch was fet by equal altitudes ; but I 

 have loft the book in which the entry was made, and 

 have only a copy of my obfervations as a regifter of 

 this and the next that follows. 



15th February, an Eclipfe of the Moon. 

 End ioh.i5 / .oo",5, apparent time correct. 



1 77°\ 3^ March, an captation o/"Regulus. 



Not having an ephemeris at the time, the obfervation 

 was accidental, and confequently not prepared for. 

 The tranfit inftrument was but lately put up, and had 

 not been much ufed, but it was the only refource for 

 time: accordingly, it was adjufted truly as to level and 

 wires, but it was not in the meridian accurately. There- 

 fore the tranfits of feveral (tars were taken to determine 

 the pofition of the inftrument, and the error of that be- 

 ing known, the times could be corrected by a very eafy 

 rule, which I fubjoin. Let x be the error in feconds at 

 the horizon, a and b the fines of the zenith diftances of 

 two ftars, a and b the fines of the polar diftances, d the 

 difference of the errors of the clock, as found from the 

 obierved and the calculated tranfit of thofe two ftars. 



x a 



Then will be the fpace at the equator for the equa- 



A v b 



tion to correel; one, and- the fame for the other : 



B 



and the fum of thefe two will be equal to ^-L-15. or, 



which is the fame thing, 1 =d. Whence for 



15 A l 5 B 



all fmall angles *— 15 "*~ f + A B 



a 11 -{- b a. 



^ and y Leonis were the two ftars that were relied on 

 for time and pofition, becaufe they pafs fo nearly at 

 equal diftances from the zenith, that the mean of their 

 errors of the clock would be fo near to the true one, 



that 



