the Latitude and Longitude of York. 419 
differ* 15" from the mean ; therefore, I think, we may expedfc 
a ftili greater exadnefs, perhaps within 10", if the above 
particulars be attended to. 
When the fame ftars are not obferved, it is neceflary for the 
obfervers at both places to compute their R. A. from tables, in or- 
der to get the apparent R.A. of the moon's limb ; though this is 
not fo fatisfadory as by adual obfervation, ftili the difference 
will be trifling, provided the ftars R.A.’s are accurately fettled. 
Your catalogue undoubtedly may be depended on the moft, and 
thofe ftars preferred which have their proper motions afeertained. 
A few years ago, I had the pleafure of communicating to you 
the proper motion of @ Virginis, which I found to be 1^,02 
per year, increafing in R.A. * : was this unknown, and that ftar 
obferved alone with the moon, it would occafon, at this time, 
a very confiderable error. 
I am alfo of opinion, that the fame method can be put in 
pradice by travellers with little trouble, and a tranfit inftrument 
conftruded fo as to fix up with facility in any place. Though I 
have not confidered this fufficiently, I fhall, neverthelefs, fubjoin 
a few remarks that may engage others to turn their thoughts 
more fully to the fubjed. 
It is not neceflary, perhaps, that the inftrument fhould 
be perfedly in the meridian to a few feconds of time, provided 
ftars, nearly in the fame parallel of declination with the moon, 
are obferved : nay, I am inclined to think, that if the inftru- 
ment deviates even a quarter or half of a degree, or more, 
fufficient exadnefs can be obtained,, as a table might be com- 
* Some time previous to this communication, I had found, hy the Tcomparifcn of 
my tranfit obfervations of a Aquilce and £ Virginis, that the latter had moved 
forward with a proper motion of o'', 91 of time, or of 1 3'% 65 of R.A, front 
1767 to 1783, in 16 years, or at the rats of o' 7 , 853 a year, on fuppohtiou 
that the proper motion of w Aquilje is o",57 a year forward. 
Vot. LXXVI. I 1 i puted, 
