1204 
| each time. In this way it is made probable, that the azimuthal 
impulse possesses discrete special values and the analogy with the 
case of the elliptic motion imparts special probability to the hypo-- 
thesis (96). 
Although the existence of stationary orbits is thus rendered pro 
bable, it does not follow that a particle which to begin with is not 
moving in a stationary orbit will have time and opportunity to pass 
into one. The giving off of energy requires time which is always 
available in the case of stable motion (in Lapnacr’s sense). But for 
hyperbolic motion the case is different: the energy is not limited 
by any conditions, but the rotational impulse tends towards definite 
values which can only be reached by the process of radiation of 
electromagnetic moment of momentum. For this radiation the time 
available is only the one motion past the nucleus, and it is thus 
quite possible that the impulse lost by radiation is not sufficient and 
that the particle returns to infinity without having reached a stationary 
condition. On the basis of Maxwett’s theory this would even be the 
usual case. Calculation gives for the radiated impulse (for p >> p,) 
eu’ xe 
2 / 
elas (+55) b m1 , 
pv Pr ned HE xe 
that is an amount of the order 10! erg sec., whereas the steps 
of the constant p are about 10-°7 erg sec., or about 1000 times 
larger. Under these circumstances no fraction of the particles worth 
mentioning could attain stationary orbits. 
On the other hand we have the experimental fact, mentioned in 
the previous section, that the H-atoms are preferably emitted in the 
direction of the incident a@-particles and it seems difficult to interpret 
this otherwise than on the quantum-theory. One of the possible ex- 
planations of Rurserrorp’s results seems therefore to be that the 
radiation is really stronger than would follow from Maxwerr’s theory, 
sufficiently so to carry a considerable portion of the systems into 
the stationary condition. When we consider that even in the radiation 
of the hydrogen spectrum, where the distances from the nucleus 
are greater than 2 < 10-8 ems, a considerable deviation exists from 
MaxweLr’s theory, the supposition in RUTHERFORD's case of a very 
much larger deviation does not appear to us too hazardous. For 
the distance from the nucleus is here of the order 3.5 < 10—13 and 
thus the acceleration about 1.5 X 10° times larger than in the 
emission of the hydrogen lines. Moreover Einstein *) has postulated 
a complete breach with Maxwe..’s theory for elementary processes 
3 
C 
1) A. EINSTEIN. Kleiner-Festschrift, Zürich 1918. 
