The above depiction is a colorized version of a drawing found in
Heraldry: A Pictorial Archive for Artists & Designers (Arthur Charles Fox-Davies)
[ Thanks to Guy H. Power for unearthing this one... ]
Or, on a chevron Vert three prisms Argent between two crosses pattee
of the Second in chief and a radiometer Proper in base.
On a wreath of the colors, an elephant quarterly Or and Vert bearing
two crosses patty counterchanged, the dexter paw resting on a prism Argent.
Motto: Ubi Crux, Ibi Lux. (Here the cross, there the light.)
These arms of William Crookes have a canting element, since the latin word for "cross" (crux) is pronounced like "Crookes". The whole motto clearly refers to the Maltese cross experiment depicted below:
In some reproductions of this tube, the Maltese cross [originally made out of mica] can be laid flat (out of the way). A shadow is cast because whatever comes from the cathode travels in straight lines. (The fact that an external magnetic field bends these trajectories, suggests that the rays actually consist of charged particles.)