[ 519 ] - 
and thus I compleated my whole feries of obfervatjons 
with the fe6tor, having obferved 43 different liars in all, 
on both fides of the hill, and taken 337 obfervations. 
As a few obfervations, taken with fo excellent an in- 
11 rument as this zenith fe61or, would have been fufficient 
to determine the apparent difference of latitude of the 
two nations of the obfervatory, to a fecond or two ; I 
am apprehenfive I may be thought by many to have 
multiplied obfervations unneceffarily. However that 
may be, I apprehend, that doubling the obfervations 
in each ftation of the obfervatory, by taking them with 
k ,e plane of the inftrument alternately facing the Eaft 
•and Weft, will be allowed to be a proper ftep, as the 
line of collimation of the inftrument is hereby feparately 
determined at each ftation, and thereby all danger of any 
alteration happening in the fame, in its removal from one 
lide of the hill to the other, is intirely obviated. I had, 
indeed, all the reafon in the world to think, that the 
fedtor was carried from one ftation to the other without 
the leaft accident; but ft ill it was proper to guard againft 
what was poftible to happen. 
But I had reafons alfo for multiplying the obfervations 
made in the fame pofition of the inftrument. It was im- 
portant to demonftrate the exa61nefs of the inftrument 
from the near agreement of a number of obfervations 
taken with it, as its excellence was not to be intirely pre- 
fumed, unlefs this proof could be fhewn in its favour. Be- 
ftdes, it might be expefted, that fome unfteadinefs or warp - 
VoL. LXV. Z z z ing 
f 
