[ 425 3 
variation 20| degrees allowed for), I make the dif- 
ference of longitude between them (by Mercator) to 
be 30 f miles, which is equal to 2' 2." of time : and 
recolledting your mentioning to me Dury and Bell's 
adtual Survey of London and its environs for 30 
miles, as of fome ufe for the purpofe, 1 have looked 
over it, and find by that, that the direft diftance be- 
tween Windfor Caftle and St. Paul’s, London, is 22 
ftatute or meafured miles : and by another Survey of 
the fame kind, done by Kitchen, I find the diftance 
between thofe two places to be very nearly the fame. 
Therefore, with this diftance of 22 miles, equal to 19 
geographical ones, and the difference of latitude, by 
obfervation, between the two places 2| miles, I find 
the departure to be i8,B miles, which gives 3^>^ 
miles of longitude, equal to 2' of time, agreeing 
within a fecond to the former methods 
The difference of longitude, or difference of meri- 
dians, therefore, between the Round Tower Wind- 
for Caftle, and St. Paul’s, London, I think I may 
venture to put at 30 1 miles, or t! 2!’ of time ; 
though I am perfuaded, if any thing, it is rather 
more than left j to which if we add the difference 
of longitude in time between St. Paul s and Green- 
wich, which is 22"^y it will give 2' 2^"^ of time 
for the difference of longitude between the Round 
" Tower at Windfor Caftle, and the Royal Obfervatory 
at Greenwich. 
I cannot help obferving, that the only inconvement 
circumftance, during the time of obferving the tranfit, 
was the wind 5 which, blowing rather hard, and di- 
redlly into the telefcope, together with the fmallneft 
VoL. LIX. 1 i i 
