[ 4S9 ] 
XLIV. A Comparifon of the Heat of London and Edin- 
burgh. By John Roebuck, M» D. F. R, S, in a Letter 
to William Heberden, M. D, F, R. S. 
SIR, 
Redde, June 29,y DELIVERED to you foiue time ago, 
A a regifter of the thermometer at Hawk- 
hill for ten years ; but as thefe obfervations were made 
at eight o’clock in the morning and four in the after- 
noon, and yours at eight o’clock in the morning and two 
in the afternoon, the correfponding years of the morn- 
ing’s obfervations only admit of a comparifon. It ap- 
pears by your regifter, that the mean heat at London for 
nine years, from the end of 1 763 to the end of 1772, at 
4 
O 
eight o’clockin the morning, was 47.4; and the mean heat 
at Hawkhill, during the fame period of time, was 46°.. The 
o 
difference of which is only i .4. A difference much lefs 
than might be expefted from the difference of latitude, 
and not fufflcient to account why nonpareils, golden ren- 
nets, peaches, ne6larines, and many kinds of grapes, ge- 
nerally come to maturity near London, and fcarce ever 
near Edinburgh, without the aid of artificial heat. Be- 
fore I proceeded further to perplex myfelf witli this dif- 
a ficulty,. 
