688 Sir g. shuckburgh’s Letter^ 8cc. 
I fhall now beg leave to conclude with what I flattei 
myfelf will not here appear improper, a new rule for 
reducing the obfervations, and which I hope will be 
found particularly commodious, as it requires no loga- 
rithms, nor any other than the following fliort table, 
which may be engraven upon the fcale of a thermome- 
ter, and therefore, always accompanying the inftrument, 
will ferve for computing the obfervations upon the fpot, 
(if the height fhould not exceed 4000 or 5000 feet) 
which, I apprehend, will frequently be found very fatif- 
factory. 
The adjoined table gives the value 
of — th of an inch on the barometer 
in feet in the atmofphere, when the 
quickfilver Hands at 30 inches, for 
every five degrees of temperature 
from 32° to 8o°; and for any other 
height of the barometer it will be in 
the inverfe ratio of that height to 30 
inches. Thus, let a be the mean 
height of the two barometers in 
inches; a the difference of the two 
barometers in 1 oths of an inch ; (3 the number taken out 
of the adjoined table; x the height in feet; we have then 
the following expreffion, =x, the height required. 
I have the honour to be, See. 
£ 
_C 
O • 
3 2 
Feet. -I 
85.86 
• a 
1 -O C 
1 c; <t> 
'UH 
35 
87.49 
'o .S 
40 
45 
88.54 
89.60 
.s*S s 
J- 1 rj O 
£ ~ 
a 
50 
90.66 
— -v- 
tenth of 
meter, e: 
rlien the 
:cording 
55 
91.72 
60 
6 5 
92.77 
93.82 
l s l a 
s K S" » 
u- <U -C % CJ 
O M p 
70 
CO 
CO 
• 4 * 
ON 
W 0 C 
■B § S'" 2 
75 
95 93 
> fc 3 8,8. 
O > O r* 
8c 
9 6 99 . 
pj T 3 n a 
