A preliminary demonstration on photography and fluorescence was given. A description accompanies the report on the communication made on 4th May 1896.

When Professor Röntgen's results were first made known the greatest attention was paid to the photography of objects which had previously been considered beyond the range of human vision. It is clear, however, that the discoverer did more than present us with a new photography by a force differing, in many respects, from day or artificial light. In his first paragraph he describes fluorescence on a prepared screen, and in the second he shows how one may see shadows of the bones within a faint dark shadow of the hand itself. The obvious advantage of being able to throw shadows of the deep-seated structures of the body upon screens cannot be over-estimated for medical and surgical purposes. The following experiments were undertaken with a view of contributing something to the work in this direction.

With regard to the salts employed, screens were prepared of potassium-platino-cyanide, barium-platino-cyanide, lithium-rubidium-platino-cyanide, calcium tungstate in its crystalline form (Edison), sulphide of calcium, magnesite, fluorspar, &c. In my experience it may be said at once that the potassium and bariumplatino-cyanide salts were found to be the best, although the lithium-rubidium-platino-cyanide gave an excellent picture. The fluorescence of the potassium salt is probably in advance of all others, but occasionally one seems to get at least a more pleasant picture of the deep-seated structures of the body with the barium screen, particularly when the latter has a thick coating.