BUTTERFLY “GHOSTS”

Taranaki Daily News, 28 April 1931, Page 9

BUTTERFLY “GHOSTS”

PICTURES FROM EMANATIONS. PHOTOGRAPHIC PHENOMENON. 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, were 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 affect--ed 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 iir 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 eaught,i give good results in frbhi 24 to 30 hours, Mr. Clark said, but ordinarily satisfactory results cannot be secured; except, by exposures of at least' a week.i The brightness of the image is propor-’ tionate to the length of exposure and the amount of pressure against the plate, and inversely to the age of the specimen. “Butterflies caught 30 years ago,’’ Mr. Clark said, “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 lightly-tinted South American species. The best results are obtained from very dark butterflies. . 1

‘‘Females, if coloured Hkb 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 lies, even in exposures of 30 days’ duration.”