[ 204 '] 
Hence it appears, that if the mean height of barometers, on 
a level with the furface of the Tea, be fuppofed, with Dr. 
Scheuchzer, Piiil. 'I'ranf. N“ 405, 406, 29,993 inches 
and the mean height at Caen, — ; — 29,752 ditto 
0,241 the difF. 
will be the greater mean weight of the atmofphere at the furface 
of the fea, then at Caen : and if; with the Do£ior, we allow', for 
each tenth of an inch depreffion of the quickfilver, 90 feet ele- 
vation, my room, which is in the highett part of the town, will 
be about 2 1 7 feet above the level of the fea. 
Monfieur de Luc, of Geneva, has given a method to meafure 
the different elevation of places by barometers, grounded on 
his own obfervations, far more cxa6t than any other before him ; 
his rule is, “ the difference of the logarithms of the height of 
“ the quicldilver, in the two places, reduced into French lines, 
“ and the logarithms carried to five places, including the charac- 
“ terifficks, will give the dift'erence of elevation in toifes, if 
“ Fah renheit’s thern.ometer be nearly at 66®; but about -r‘g muft 
“ be deducted from the elevation fo given, if the tnermometcr 
“ be at 53° or temperate.” 
29,993 Lnglifh inch.= 337,824 French lines log. 25286,8 
29,752 ditto =335,1 10 ditto log. 25251,9 
difF. 3+59 toifes 
or 209 4 French feet = 223 Englifli feet nearly ; from which if 
= 12 I nearly be deducted, 210 \ feet remain for the differ- 
ence of elevation of my room and the furface of the fea, which 
differs 6 | feet from the refult given by the firft hypothefis. 
The grcatefl: height obferved, in thefe five years, with a good 
Fahrenheit’s thermometer fereened from the fun, in a S. W. 
room, was as follows at noon : 
I 765 Auguft 23d 1 
1766 Auguft 9th r* 76° 
1765 June ythJ 
the leaft height of ditto Jan. 6th 1768 — — 14 
1765 Auguft 23, expofed the thermometer, at noon, to the fun, 
fufpended on a thread between two flicks, in the middle of my 
garden at Caen, which may be about two Englilh' acres, fo that 
the thermometer received the leaft reflected heat poftible in that 
place; the quickfilver ftood as follows. 
at 
