Page:Proceedings of the Royal Society of London Vol 60.djvu/192

Rh Grating B.—Breadth of strip = 1·5 cm.

Grating C.—Breadth of strip = 2 cm.

Grating D.—Breadth of strip = 2·5 cm.

Grating E.—Breadth of strip = 3 cm.

It would thus be seen that the different values of wave-length obtained from the above experiments are concordant, the mean value being 1·846 cm.

I then carefully removed the electrical vibrator, and measured approximately the size of the sparking balls. The radiator, it must be remembered, was placed vertically inside a square tube, each of whose sides is 2·5 cm. The radiator was about 1 cm. inside from the free end of the tube.