Authentic Science Fiction Monthly, No. 65 — page 122: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

AUTHENTIC SCIENCE FICTION visible to the human eye, nor do they show up on pan- _ chromatic plates. But if the leaves are photographed by infra-red radiation on infra- red-sensitive plates, the ne- croses show up as jet black patches on a white leaf. Again, in a study of a leaf disease of the cherry tree known as gummosis, it was found very difficult to detect which leaves were affected and which were healthy. When infra-red photography was resorted to, the diseased leaves showed up dark against a light back- ground of healthy leaves. Infra-red photography has, of course, many applications in medicine. Among other uses it reveals the extent of varicose conditions and skin diseases ; and has greatly facili- tated examination of the eye - by revealing defects which otherwise might escape detec- tion by normal visual examination. Before the days of print, monks and other learned people penned their writings on sheets of parchment. Very often parchment was in short supply so the learned scribes erased the writing from pre- viously used parchment and used it again. In this way, many important documents, or rather writings, were lost. Such twice-used parchments are called palimpsets, and generally speaking, it is im- possible to see the original writing. But. if a palimpset is sub- jected to ultra-violet light it glows with a soft bluish visible light. Those parts which have never been written on glow more strongly than those which are, or have been. If a photograph is taken of the fluorescent light from the parchment, the ori- ginal writing is revealed. Photographs made in _ this way have often proved of value in detecting forgeries and in studying changes in old paintings. Infra-red photography is resorted to in cases where cheques, bank notes and docu- ments have been charred by fire and the writing and other details upon them rendered indecipherable. In the photo- graphic print, that which was invisible on the charred origi- nal is clearly visible 121 comicloooks.corn