548 
PROFESSOR DANIELL ON THE WATER-BAROMETER ERECTED 
Table of Corrections for Temperature for the Water-Barometer. Standard 
Temperature of Scale 60°. Maximum Density of Water 40°. 
Temperature. 
Inches. 
350 
Inches. 
360 
Inches. 
370 
Inches. 
380 
Inches. 
390 
Inches. 
400 
Inches. 
410 
Exact. 
Approx, 
35-6 
35 
—•101 
-•103 
— •106 
— •108 
— •112 
— •115 
—•118 
39-38 
40 
— •072 
-•074 
-•077 
-•079 
—•081 
— •083 
-•085 
44-6 
45 
—•073 
—•075 
-•077 
-•079 
-•081 
— •083 
— •085 
50 
50 
— •113 
— •115 
— •118 
— •122 
— •124 
— •128 
-•132 
55-4 
55 
-•191 
-•195 
— •201 
—•206 
— •211 
—•217 
-•223 
59 
60 
—•258 
—•264 
—•272 
-*279 
—•286 
— •294 
— •302 
64-4 
65 
-•398 
-•409 
— •420 
— •431 
—443 
— •454 
—466 
69-5 
70 
—•575 
-•590 
— •606 
— •623 
-•639 
—*656 
-•673 
75-2 
75 
— •786 
— •808 
— •831 
—•853 
— •876 
-•898 
-921 
With regard to the capillary action of the tube, which of course is in the 
opposite direction to that of the mercurial barometer, Dr. Young has calcu¬ 
lated * that the central elevation for water in a tube of which the diameter is 
•49964 inch (which is almost exactly the diameter of the tube within the range 
of the oscillations,) is ‘035, and the marginal elevation T72. 
In my first use of the instrument I conceived that the observation was made 
with most certainty by bringing the vernier to coincide with the marginal ele¬ 
vation of the water ; and in the following observations the correction of — T7 
has been applied accordingly. Mr. Hudson has since shown me, that by re¬ 
flecting the light upon the column from behind, the observation from the centre 
is made with the greatest precision ; and in some observations which have been 
kindly furnished by that gentleman, the correction of —’03 only has been 
applied. The difference of the two corrections deduced from the calculation 
of Dr. Young as above, agrees very nearly with the difference of the two read¬ 
ings upon the barometer when carefully observed. 
As the usual Tables for the thermometric correction of the mercurial baro¬ 
meter are calculated for 32°, I considered it necessary to calculate a fresh 
Table for the temperature of 40° ; that both the water and the mercury might 
be reduced to the same standard temperature. The dilatation in volume of 
mercury per degree of Fahrenheit has been taken, on the authority of MM. 
Dulong and Petit, at •0001001 of the volume at 32°. And the height of the 
* Young’s Lectures on Natural Philosophy, vol. ii. p. 669. 
