C 251 ] \ ' 
fiver, and n denote the difference of the temperature 
of the air , in degrees of his own fcale , above or 
below 4- i6f, then L± — L, is the difference of 
^ x 5 , 
elevation in 1000 ths of a Paris toife. The correction 
PI— L, to be added or fubtraCled , according as the 
temperature oj the air is above or below i6| ; or ac- 
cording as n is a difference in excefs or defettW, 
But in any given value of n , the proportion of 
L to L is given, being that of n to 215. There- 
n 
2X5 
fore, L ± L is the logarithm of the ratio of 
the heights of the barometer, in a fyftem of loga- 
rithms, in which the fubtangent of the curve is to 
fo many ioooths of a Paris toife, as are expreffed 
by the fubtangent of the Briggian fyftem, as 
215 ± n to 215. And this being the cafe, what- 
ever be the value of L, in every given value of n , 
it is evident, that the variation of the modulus ot 
the atmofpherical fyftem, or of the fubtangent 
of the atmofpherical curve, is always as n 3 the varia- 
tion of temperature. 
But a uniform temperature is a condition of the 
atmofphere, which rarely obtains, within fmall 
diftances, at leaft, above the earth’s furface ; therefore 
the more ufuai cafe of unequal temperatures muft 
be confidered. 
When different temperatures obtain, at different 
heights, at the fame time, they muft render the 
abfolute elafticities, at thofe heights, unequal. 
Thus the hypothefis of M. boUguer will take place ; 
(?) Recherch. far les Modif. de l’Atcn. §. 607—611. 
K k 2 whq* 
