156 Dr. Maskelyne’s Olfervations on the Latitude 
vatory from his obfervations, according to tiie manner above 
explained; in which he firft fiates it at 51 0 28' 38", and 
finally more correCtly in thefe words. “ The apparent zenith 
“ diftance of the equator, by the mean of 20 obfervations in 
44 1746-47, 2j' 28 // . The mean apparent difiance of the 
“ pole, by the obfervations made between 1 750-52, 38° 30' 35 b 
44 Sum 89° 58' 3". Sum of refraCtions i' S']"* Polar refrac- 
“ tion o' 45 // |. Equatorial refraCtion 1' \i n \. Latitude 
“ 51 0 28' 39"*. Co-latitude 38° 3 i' 20 
The latitude of the Obfervatory being thus fettled, as well 
as the quantity of refractions for all fiars palling the meridian 
between the pole and the equator, Dr. Bradley readily 
inferred from his obfervations the true difiance of all fuch 
■ r 
fiars from the north pole, which, compared with their zenith 
difiances obferved below the pole, gave the refraCtions at 
thofe lower altitudes. Finally, by comparing the refractions 
together obferved in extreme degrees of heat and cold, he 
deduced the law of their variation as affeCted by heat and 
cold; and thus at length he inferred his elegant rule for 
determining the refraction in all circumfiances, that it is to 
57", in the direCt compound ratio of the tangent of the 
apparent zenith difiance lefiened by 3 times the refraCtion to 
the radius, and of the height of the barometer in inches to 29,6 
inches, and in the inverfe ratio of the degree of height of 
Fa hrenheit’s thermometer increafed by 350 to 400. 
But it may be proper to confirm this rule for refraCtions alfo 
from the fame manufeript of Dr. Bradley, which I before 
cited for confirming the latitude, by the following paflage, 
which immediately follows the other. “ Suppofe the 
“ mean refraClion at 45 0 3' = 57", and y = 350 ; then 
“jy-b/: bar. 77" : refr. at 45 0 3'. 
“ Rad. 
