ed that the rays carry a
charge of negative electricity, and M'Lennan measured the amount of
ionization rays of given intensity produced in different gases, finding
that if the pressure is adjusted so that the density of the different
gases is the same the number of ions per cubic centimetre is also the
same. In this case, as Lenard has shown, the absorption is the same, so
that with the Lenard rays, as with uranium and probably with Rontgen
rays, equal absorption corresponds to equal ionization. A convenient
method for producing Lenard rays of great intensity has been described
by Des Coudres (_Wied. Ann._ 62, p. 134).

_Diffuse Reflection of Cathode Rays._--When cathode rays fall upon a
surface, whether of an insulator or a conductor, cathode rays start from
the surface in all directions. This phenomenon, which was discovered by
Goldstein (_Wied. Ann._ 62, p. 134), has been investigated by Starke
(_Wied. Ann._ 66, p. 49; _Ann. der Phys._ 111, p. 75), Austin and Starke
(_Ann. der Phys._ 9, p. 271), Campbell-Swinton (_Proc. Roy. Soc._ 64, p.
377), Merritt (_Phys. Rev._ 7, p. 217) and Gehrcke (_Ann. der Phys._ 8,
p. 81); it is often regarded as analogous to the diffuse reflection of
light from such a surface as gypsum, and is spoken of as the diffuse
reflection of the cathode rays. According to Merritt and Austin and
Starke the deviation in a magnetic field of these reflected rays is the
same as that of the incident rays. The experiments, however, were
confined to rays reflected so that the angle of reflection was nearly
equal to that of incidence. Gehrcke showed that among the reflected rays
there were a large number which had a much smaller velocity than the
incident ones. According to Campbell-Swinton the "diffuse" reflection is
accompanied by a certain amount of "specular" reflection. Lenard, who
used slower cathode rays than Austin and Starke, could not detect in the
scattered rays any with velocities comparable with that of the incident
rays; he obtained copious supplies of slow rays whose speed did not
depend on the angle of incidence of the primary rays (_Ann. der Phys._
15, p. 485). When the angle of incidence is very oblique the surface
struck by the rays gets positively charged, showing that the secondary
rays are more numerous than the primary.

_Repulsion of two Cathode Streams._--Goldstein discovered that if in a
tube there are two cathodes connected together, the cathodic rays from
one cathode are deflect