556 Sir george shuckburgh’s Obfervations 
The titles of the columns are fufficiently clear to make 
a farther explanation of this table unneceflary; and it 
appears, I think inconteffably, upon taking a mean of my 
thirteen obfervations (and I fhall here confider only my 
own) on Mont Saleve and the Mole, that this error is 
about 23-i feet on every thoufand; that is, the rules of 
Mr. de luc give the height by l'o much too little. At 
the bottom of the foregoing table 1 have fubjoined fix 
other comparifons, fome of them from Mr. de luc’s 
own obfervations, as recorded in his valuable work; 
which however I muft add, are certainly of lefs autho- 
rity in this inquiry, as they were made with barometers 
a great way diflant from each other, viz. near thirty 
miles: befides which, the geometiical heights are, for 
the fame reafon, not fo accurately afcertained. I have, 
however, ventured to make what ufe I could of them, 
viz. to fhew that thefe two give a refult on the fame 
fide, though not exactly the fame ; and to urge the ne- 
ceflity of a certain vicinity in thofe obfervations from 
whence a theory is to be deduced. 
Shall I be permitted to adduce another proof, in con- 
firmation of what has been advanced ? When I firft took 
up the confideration of meafuring altitudes in the atmo- 
fphere with the barometer, and had heard only of Mr. 
de luc’s labours, it occurred to me, that there was a 
6 much 
