Feb. 17,1888.] 



SCIENTIFIC NEWS. 



149 



PHOTOGRAPHY BY FLASH-LIGHT. 



TAKING a photograph by means of a flash-light 

 generated by the deflagration of various explosive 

 compounds is no new idea, but owing to a recent dis- 

 covery by Dr. Henry G. Piffard, of New Yorlv, the process 

 has become not only exceedingly simple, but also per- 

 fectly safe, a recommendation that could hardly be given 

 to the previous explosive mixtures used for the purpose, 

 containing as they usually did potassium chlorate in con- 

 siderable quantities, a material that is liable to ignition 

 from percussion or friction. 



One of the earliest compounds of this type was 

 introduced by Gadicke and Meithe, and consisted of 

 magnesium powder, potassium chlorate, and sulphide of 

 antimony, and no doubt very good results were obtained 



photograph of an animal, such as the common or garden 

 cat, illustrated below, an exceedingly small gun-cotton 

 disc was necessary, owing to the rapidity with which 

 Felis doniesticus shrinks from the vivid flash. The illus- 

 tration depicts a very placid-looking animal, but the 

 hghtning-like velocity with which the victim vacates its 

 position when the flash takes place has to be seen to be 

 thoroughly believed. However, no matter what the 

 agility of the " subject," the flash comes in an easy 

 winner if kept, as above stated, of small dimensions. 



The cost of producing this light is trifling ; for instance, 

 the above photograph was taken with gun-cotton and 

 magnesium powder, weighing together under two grains ! 

 retail price about half-a-crown an ounce; it was, how- 

 ever, ignited within two feet of the " subject," the lens 

 used was a very rapid "Suter" lens with full aperture, 



Photograph of Manx Cat taken by Flash Light. 



by its use. The use of magnesium powder mixed with 

 fine sand, to separate the particles, allowed to fall in the 

 form of a stream into the flame of a spirit lamp ; and 

 also the well-known magnesium ribbon hardly come 

 within the category of flash-lights, as the duration of 

 the exposure of the sensitive plate necessary to produce 

 a good negative is measured by seconds, but may be men- 

 tioned as leading up to Dr. Piffard's neat little discovery. 

 This device is simplicity itself : a small lock of gun- 

 cotton is taken, and the fibres loosened and pulled apart 

 until it forms a light disc of about two inches diameter, 

 and then the finest magnesium powder is lightly sprmkled 

 over it, and the powdered wad is ready to be flashed off 

 at any moment by the application of a lighted taper. 

 The size of the wad necessary is of course regulated by 

 the subject to be photographed ; for portraits the wad may 

 be three or four inches in diameter, which will give a 

 full exposure to ordinary rapid gelatine plates, but the 

 writer found in his experiments that to get a sharp 



and the gelatine plate was one of Messrs. Elliot and Fry's 

 ordinary commercial plates for rapid photography. 



For portraits from 15 to 20 grains of cotton and powder 

 combined, or even more, may be used with advantage, as 

 the light has to be kept further from the "subject," and has 

 also to be toned down and carefully reflected to eliminate 

 hard shadows and obtain artistic results. A human 

 being is not nearly as quick as a cat in getting his facial 

 muscles in motion, but the writer finds that, after having 

 once half blinded his human subject with the magnesium 

 flash, it is almost impossible to prevent him screwing 

 up his eyes before the next flash ; now a cat never seems 

 to learn that a lighted taper is the precursor of a blinding 

 flash, so it reserves its grimaces until it is too late to 

 have them recorded on the faithful gelatine; and we are 

 led to the not unreasonable deduction that there is a 

 difference of reasoning power in the two " subjects,' 

 not that we wish to cast any slur on our feline sitter, for 

 he is a Manx tom of exceptional intelligence. 



