[eve] IONS PRODUCED BY THE BETA RAYS 79 
As about 3-410" g particles leave a curie of radium C every 
second, there will be the same number of y pulses, and we have 3-4X 
10” X -0156, or 5108 ergs per second as a very moderate estimate 
of the power of the y radiation. 
But the whole power of all the radiations from a gramme of radium 
is only 1-3x10° ergs per second. 
It therefore seems impossible to consider the y radiation as a 
spherical shell with uniform energy over the surface, and also impossible 
to contemplate the + radiation as expanding conically. It must be 
linear, whether electromagnetic or corpuscular. As the 7 radiation is 
mainly independent of the concentration at the source, it does not seem 
possible to conjure up a train of pulses, or overlapping of pulses, or any 
such interference effects to account for the energy necessary for loniza- 
tion. 
It seems, then, correct to speak of a y ray in the sense of a definite 
entity carrying energy in a linear path, unless indeed some of the energy 
of ionization comes from the molecule ionized, a view which is generally 
rejected. 
Summary. 
1. The value of the constant K’, which may be given the theoretica! 
definition of the number of ions produced per em. per second at a 
distance of 1 em. from a curie of radium C, in air at atmospheric pressure, 
is 3-74%10°. The total number of ions per second which a curie of 
radium C could produce in air at atmospheric pressure is N’=1-1x10". 
2. Corresponding values for the B rays have been found; namely 
kK f-310" and. N—4-0X 10": 
3. Hence, the total number of ions made by one B particle in an 
average flight from radium C in the atmosphere is 1-2x10*, equivalent 
to about 48 ions per cm. Hence, the g particle must pass through about 
180 molecules for every one which it ionizes, if the radius of a molecule 
is 10-8cem. The values in (2) and (3) are only approximations. 
4. If the y ray is an entity with a linear path, the total ions per 
entity are 3 x 10‘ for an average flight, and 1-2 ions per em. of path. 
5. The heating effect of the 8 and @ rays may be calculated on the 
assumption that ionization is a measure of the energy expended. Ifa 
gramme of radium, and its four succeeding products, have a heating 
effect of 110 calories per hour, then the distribution is somewhat as 
follows:— 
