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TRANSACTIONS OF SECTION A. ‘709 
some exhibiting orbits of oscillating satellites, and orbits with cusps and loops. 
Perhaps the most curious cases are those representing the orbits of satellites, which 
present three new moons in a month, and another with five full moons in a month. 
The consideration of the stability of the orbits shows that there are stable 
satellites close to Jove, or at some distance from Jove; but that there is a tract 
between these two in which no stable motion can take place. This conclusion 
appears to throw some light on Bode’s empirical law as to the distribution of 
planets and satellites. 
A paper containing an account of this investigation will appear in the Acta 
Mathematica of Stockholm. Se en 
FRIDAY, SEPTEMBER 18. 
The following Papers were read :— 
1. On Cathode Rays and their probable connection with Réintgen Rays. 
By Professor Puiriep Lenarp, Aachen. 
Until a few years ago it was impossible to make experiments on cathode rays 
under modified conditions, because it was impossible to vary their surroundings 
without at the same time altering the circumstances under which they were pro- 
duced. Hertz’s discovery that thin sheets of metals were transparent to the 
cathode rays has enlarged the field of experiment. By making a small aluminium 
window in one end of the discharge-tube the rays can now be allowed to go out 
from the space where they were generated ; they can thus be investigated without 
altering the conditions of generation, and therewith the properties of the rays 
themselves. The cathode rays emerge into air at ordinary pressure, but they are 
very rapidly absorbed by it, so that at a distance of from 6 to 8 centimetres no 
trace of them is visible on a screen capable of phosphorescence. The free atmo- 
sphere proves, moreover, to be a turbid medium to these rays, their propagation 
behind shadow-casting objects being similar to the propagation of light in milk. 
Other gases of equal density behave in the same way. But as the density of a gas 
is diminished by lowering its pressure, it becomes more transparent and less 
turbid. In the highest vacuum that can be produced there is no limit to the 
transmission of the rays, and behind a diaphragm they are quite as sharp as rays 
of light are under the same circumstances. From the fact that the rays are not 
stopped by a space containing only minute traces of matter it is concluded that 
they are processes going on in the ether. 
The absorption of the rays in various substances can also be investigated. It 
is found to be in every case approximately proportional to the density of the 
medium, whether this be solid or gaseous, and whatever be its chemical nature. 
The rays are deflected by a magnet, and it was found that in this respect there 
were different kinds of cathode rays, those which are produced when the dis- 
charge-tube was more exhausted being less deflectible than those produced when 
it was less exhausted. The deflectibility of the rays depends also in other respects 
on the circumstances of their production ; it is, however, quite unalterable by any 
change in the observing-space. Whatever the nature or the pressure of the gas in 
this space was, the deflectibility of the rays remained the same whenever it could 
be tested—z.e. whenever the density of the gas was such as allowed rays of some 
sharpness to be obtained. This was the case, for instance, in common air below 
about one tenth of an atmosphere, and in hydrogen of ordinary or any smaller 
pressure. The deflectibility of the rays was also found to be the same before and 
after traversing an air-tight sheet of aluminium set up in the observing-space. 
The deflectibility of a cathode ray once produced being thus quite unalterable, 
its magnitude may serve as a characteristic to denote any particular kind of cathode 
tay. Rays of smaller deflectibility were found to be less easily absorbed and 
