The composition of the x-rays from various metals

In a paper published in the ‘Philosophical Transactions’ in 1908, the writer described some experiments on the X-rays emitted by a variety of metals when used as anticathodes in an X-ray bulb. Among the results established was the homogeneity of a large proportion of the X-rays when the bulb was very “soft.” The absorption curves of the several homogeneous radiations revealed their identities with the characteristic “secondary” radiations which Barkla and Sadler had then recently discovered. The experiments described in the present paper are an extension of the above, and were carried out partly at the Cavendish Laboratory in 1908 and partly at the National Physical Laboratory just prior to the war. The writer’s military duties have prevented the continuation of the work, and the results are now put on record in the hope that they may help to further the progress of the subject, to which the more precise method of the crystal-spectrometer has given a great impetus from a different point of view.