meafuring Heights with the Barometer , 745 
meter throughout the year ; the uniformity of the mean 
temperature in every affigned ftation ; and his mode of 
computing, by means of the tables of common loga- 
rithms, the altitudes of the Cordillero mountains above 
the valley that extends itfelf between them ; it will be 
no difficult matter to difcover, nearly at leaft, what fort 
of equation became neceffary ; and what were the rela- 
tive weights of quickfilver and air of the mean tempe- 
rature, not only in that high region of the atmofphere, 
but alfo at the level of the fea. 
Thus, by infpefting the table of computations, it will 
appear, that columns of air, whofe bafes were removed 
fix or eight thoufand feet from the level of the fea, and 
whofe heights equalled that diftance, when the tempera- 
ture was 55 0 of Fahrenheit, as determined from the 
mean between the coldeft of the morning and hotteft of 
the afternoon, the mean logarithmic defedt was only ^ : 
whereas, in meafuring heights near the level of the fea, 
in middle latitudes, the common equation for that tem- 
perature is about The mean ratio of the weight of 
quickfilver to air, on thefe long columns comprehended 
refpedtively between Carabourou and Quito, and the 
mean heat in any affigned ftation, it continues uniformly the fame throughout 
the year. In this rough eftimation of the temperature in Peru, it feented unn~ 
eeflary to examine, whether the true thermometer of reaumur. was uieJ or no., 
as it could produce no material difference, except at the very hotteft Hattons. 
F c r, fummits 
