meafuring Heights with the Barometer . 7 rt 
The total expanlion 484.21 refulting from the third 
clafs of experiments, which are very confident among 
themfelves, being divided into parts proportionable to 
the manometrical fpaces, as meafured in degrees of the 
quickfilver thermometer, we have the expansions for in- 
termediate temperatures, expreffed at the bottom of the 
third table, where, it is to be obferved, the rates for every 
io° below 9 2 0 were found by interpolation. 
Now as barometrical obfervations will probably never 
be made in a temperature higher than 92 0 in the Shade, 
nor in one lower than 12 0 , if we fubtradt 26.038, the 
expanfion anfwering to 1 2 0 , from 2 22.006, that which 
correfponds to 92°, we Shall have 195.968 for the 
80 intermediate degrees; or 2.45 for the mean rate 
on each. This equation, compared with Mr. de luc's, 
hears the proportion of 245 to 210, which is a difference 
of y^ qq ' qq on every degree, or one-feventh part of the 
whole : and though this rate will be found hereafter to 
feet long. Had It been pofiible to have managed them of double or triple that 
length, fo as to have admitted the air to be prefied with a column of 18 or 20 
feet of quickfilver, I am perfuaded the diminution in the expanfion of air of 
that extraordinary denfity would have been much more perceptible. 
Mr. amontons found, that the condenfation of air in his thermometers 
kept pace with that of fpirit of wine, which we are told follows a decreafing 
progrefiion with refpe£l to quickfilver: wherefore his experiments agree wita 
thefe, in making the condenfation of air below 57 0 follow a decreafing pro- 
grefiion, when compared with that of quickfilver. 
Vol. LXVIL 4 Y 
exceed 
