236 J. Lewis on the Barometer. 
the general application of this expression to the computation of 
2(=--1) . 
the compensation of the syphon, the expression is Hazy’ m 
which H is made successively equal to 82, 31, 30, 29, &e., as far 
as it may be necessary to proceed. The difference in value 0 
the numerator and denominator of this fraction, represents the 
error of temperature for 212°. _ Regarding the expression 
2( 5-1 
Hasy being but a fractional portion of the required 
unit of excess of elevation for temperature, it will be understood 
that the volume of mercury which it represents may have ws 
the form of a solid of revolution, the smaller end at top. The 
lines of vertical section of this solid are curves, the asymptote 
of which is the axis of the tube. The diameter of the conical 
chamber, beginning at top and measuring at intervals of half an 
inch, are in the following values, which relate to the origina 
unit of diameter: 
1 lam 
0-0 inch. diameter, 0:926629 
ys ve 0°941456 
a0: ~ 0°957017 
16..% - 0973379 
pt = 9060 
; | liad bed 1:008785 
‘ 30. * = 1:028002 
> 76 + “« 04835 me 
40 4 = 1:069975 
4 
The eurve which defines the outlines of the chamber 1s 80 
slight a departure from a right line (0:004433 in the limits of 
the available part of the cavity 
= line in the calb 
solid of revolution without 
e cubic space as an equa 
nd it must therefore have the same 
x = base of cone, d = truncated top _ 
di , the wa w?-+-de+d? 4 
( ameters), the value of a may be found from es eae 
z= 1071618. This value occurs between the diameters 1069975 s 
oe 1092992, and its location is determined by the proportion — 
length of the original tube, a 
mean sectional area - make 
