ON ENERGY OF EONTGEN AND BECQUEEEL RAYS, ETC. 
47 
The following table gives tlie values of i, H, and W for different times of the 
exposure to the rays:— 
Time of 
to 
exposu'e 
rays. 
i in electrostatic 
units. 
H 
in 
calories. 
tY in ergs. 
45 
secs. 
■S94 
1 
49 
X 
10-^ 
2 
* 22 
X 
10- 
-10 
•976 
1 
56 
X 
10-i 
2 
•13 
X 
10- 
-10 
1 ■ 045 
1 
47 
X 
10-i 
1 
•87 
X 
10- 
10 
1-115 
1 
57 
X 
lo-i 
1 
•82 
X 
10- 
-10 
•996 
1 
38 
X 
10-^ 
1 
•84 
X 
10- 
-ly 
30 
secs. 
1 -00 
1 
34 
X 
10-+ 
1 
-79 
X 
10- 
-10 
1-07 
s. 1 
47 
X 
10-1 
1 
•83 
X 
10- 
-10 
1-03 
1 
45 
X 
10--* 
1 
•87 
X 
10- 
-10 
5' 
1-09 
1 
41 
X 
10^1 
1 
•72 
X 
10- 
-10 
The mean value of W, the energy required to produce an ion in air at atmospheric 
pressure and temperature, is given 1)y 
W = 1-90 X 10-10 erg. 
The energy required to produce a positive and a negative ion from a neutral 
molecide is twice tliis amount, and since one ion cannot lie produced without the 
other, then 3'8 X 10“lo erg is the smallest amount of energy tliat will jiroduce 
ions in air. 
The mean intensity of the rays in aljsolute measure at the surface of the bolo¬ 
meter is given liy 
JH = ■98AIj(l — Pi). 
Taking the value of H as 1‘5 X 10 calorie, we find that 
Ij = 127 ergs. 
On account of the very short duration oi‘ the rays from each discharge, the 
maximum intensity of the radiation at any time is probably over a thousand times 
greater than the above value. 
i 
The energy absorbed per second in producing ions in the cylinder = - W = '29 
erg, taking i = 1 E.S. unit. 
This absorption of energy is spread throughout a volume of over 100 cub. centims. 
of the gas, so that tlie ab.sorjition of energy per cub. centim. in the air is very 
■small. 
The value of W, the ionic energy, is seen to depend on tlie measurement of the 
current through the gas, the coefficient of absorption, and the heating effect of the 
rays. The absorption of the rays in the gas lias to be determined separately from 
the current and heating effect, and an uncertainty consequently arises on account of 
