THERMAL EFFECTS OF FLUIDS IN MOTION. 
353 
Comparison of Air-thermometer with Absolute Scale. 
Temperature by 
absolute scale in 
Cent, degrees 
from the freezing- 
point. 
t- 273 - 7 . 
Temperature Centi- 
tigrade by constant- 
volume thermometer 
with air of specific 
•. 4> 
gravity — . 
V 
6 ion Pt ~ P ‘ !r ‘ 3 " ! 
Temperature Centi- 
grade by constant- 
pressure air-thermo- 
meter 
^ — 100 Vt V 373‘7 
P373-7~P273-7 
v 373-7~ v 273-7 
O 
0 
o 
0 
0 
20 
20 + - 0298 x - 
V 
20 + -0404 
40 
40 + -0403 „ 
40 + -0477 „ 
60 
60 + ‘0366 „ 
60 + -0467 „ 
80 
80 + -0223 „ 
80 + -0277 „ 
100 
100 + -0000 „ 
100+-0000 „ 
120 
120 — *0284 „ 
120--0339 „ 
140 
140 — -0615 „ 
140--0721 „ 
160 
160--0983 „ 
160 — *1 134 „ 
180 
180— -1382 „ 
180 — *1571 „ 
200 
200--1796 „ 
200--2018 „ 
220 
220 — -2232 „ 
220 — *2478 „ 
240 
240 --2663 „ 
240 --2932 „ 
260 
260--3141 „ 
260 — *3420 „ 
280 
280— *3610 „ 
280 — *3897 „ 
300 
300— -4085 „ 
300 — *4377 „ 
The standard defined by Regnault is that of the constant-volume air-thermometer, 
with air at the density which it has when at the freezing-point under the pressure of 
760 mm. or 22'9218 inches of mercury, and its indications are shown in comparison 
with the absolute scale by taking ^ = 1 in the second column of the preceding Table. 
The greatest discrepance between 0° and 100° Cent, amounts to less than -^th of a 
degree, and the discrepance at 300° Cent, is only four-tenths. The discrepancies of 
the constant-pressure air-thermometer, when the pressure is equal to the standard 
atmospheric pressure, or ^ = 1, are somewhat greater, but still very small. 
Section V. Physical Properties of Air expressed according to the absolute Thermo- 
dynamic scale of Temperature. 
All the physical properties of a fluid of given constitution are completely fixed 
when its density and temperature are specified ; and as it is these qualities which 
we can most conveniently regard as being immediately adjustable in any arbitrary 
manner, we shall generally consider them as the independent variables in formulae 
expressing the pressure, the specific heats, and other properties of the particular fluid 
in any physical condition. 
Let v be the volume (in cubic feet) of a unit mass (one pound) of the fluid, and t 
its absolute temperature; and let p be its pressure in the condition defined by these 
elements. 
2 z 
MDCCCLIV. 
