C J 
twenty feconds per day nearly. The greatefi part of 
the altitudes taken tor that purpofe, with a good 
Hadley’s quadrant, in a faucer of treacle and water, 
covered with your glafs roof, when neceflary, to 
fcreen it from the wind, which' I found to be of 
great ufe, are herewith inclofed, with their cor- 
refponding times, &c. which have all been com- 
pared feparately, in compliance with your requeft, 
both by Captain Schomberg and myfelf j and which 
I hope will be found to be fatisfacftory. 
As to the longitude of Windlor Caftle from 
Greenwich, which has fo long engaged my atten- 
tion, though I have not had an opportunity of af- 
certaining it with your tranfit-inftrument, by the me- 
thod of differences of azimuths, which I have long 
wanted to do, yet, notwithftanding, by a mean of 
feveral bearings of St. Paul’s, taken from the corner 
of the terras, near the dial, with a good theodolite, 
and found to be N. 82° 30' from the true meridian, 
and the difference of latitude between that cathedral 
and Windfor Cahle 2| geographical miles, think it 
may be very nearly determined j and in the follow- 
ing manner. 
The latitude of St. Paul’s, or, which is the fame 
thing, of the Royal Mathematical School in Chrift’s 
Hofpital, by the mean of a great number of obferva- 
tions, I make to be 51° 30'! N. and by a mean of 
feveral double altitudes of the Sun, taken in a faucer 
of treacle and w'ater, fcreened from the wind, I find 
the latitude of Windfor Caftle to be 51® 28'! N. 
the difference of latitude therefore between thofe two 
places is 2^ geographical miles ; with which, and 
the bearing of St. Paul’s from the Caftle N. 82° 30' E. 
(variation 
