BUTTERFLY "GHOSTS."

Auckland Star, Volume LXII, Issue 96, 24 April 1931, Page 11 (Supplement)

BUTTERFLY "GHOSTS."

PICTURES FROM EMANATIONS.

PHOTOGRAPHIC PHENOMENON

MYSTERIOUSLY PRODUCED IMAGES

Weird "ghost pictures" of butterflies, some dead for fifty years, produced on a photographic plate by some mysterious emanation, which in earlier days might have been called an escaping soul, Avere displayed before the American Association for the Advancement of Science at Washington by Austin H. Clark, of the United States National Museum. While the nature of this emanation, which affects a plate like light, has not been determined, there are indications, Mr. Clark said, that it is a gas containing sulphur, originally a constituent of the wing pigments, which is produced by the decomposition of the bodies. The fact that it will not pass through glass or quartz renders improbable the thesis of some organic light radiation. Furthermore, Mr. Clark said, butterfly wings produce an image on burnished metallic silver which is strongly affected by sulphur. The method of producing the pictures is to place the butterfly wings on glass and then place the plate, emulsion side down, upon them. They are left in total darkness. Then the plates are developed and prints made, just as if the negatives had been exposed with a camera. Very dark butterflies, freshly caught, give good results in from 24 to 30 hours, Mr. Clark said, but ordinarily satisfactory results cannot be secured except by exposures of at least a week. The brightness of the image is proportionate to the length of exposure and the amount of pressure against the plate, and inversely to th'j age of the specimen. "Butterflies caught 30 years ago," Mr. Clark sail, "gave quite recognisable, though faint images. One caught 50 years ago gave an image which showed little more than the shape of the wings, but unfortunately this was a lightlytinted South American species. The best results are obtained from very dark butterflies. "Females, if coloured like males, usually give a brighter image because of the heavier pigmentation. Nearly all the 47 species used gave equally good and strictly comparable results. The upper surface of the common white cabbage butterfly affected the plate as if it were a very dark instead of a white insect. "If this phenomenon were due to light of a very short wave-length—a sort of invisible phosphorescence —this light should pass readily through quartz, but the quartz completely obliterates those portions of the wings over which it jies, even in exposures of 30 days' duration." '