Photography In Colors

The fixing in the camera of the r.::.tural colprs of a picture li; be6s the philosopher's stone of the pliotojr. and ever and anon the statement is given out that this much-dcsired (?oaJ h;is been attained, to be quiokly i il! i wed by a description which goes to show how f ar from its promise the act'ial result of the supposed diseovery really is. M. Lippmann has, however, now put before the French Acadcmy of Sciences a plan which, if the statements made concerning it are substantiatecl. will constitute a distinct step toward the solution of the problem of photographing objccts in their natural colora. The sug-gêsted process is very simple, and involvoá the use of the ordinary reagtints. The sensitive film. during exposure, is lioated on the surface of mercury. Suppose, for instance, a ray of blue llght strikes the sensitive film, it will pass through and, being reflected f rom tlie surface of the mercury behind, will pass out through the film again interfering on its way with the incident ray. When the two rays are in the same phase their effects will be alditive, and the sensitive matter in the film will be strongly acted on. At a small distance farther on the two rays will neutralize each other so that the film is fchere totally unacted on. In tliis way the thickness of the film is divided up into layers, on which the light has aoted, half a wave-length apart, and henee when fixed and dried it may be considere:! as consisting of a number of thin platea oí' half the wave-lengthof blue light in thickness, and will, therefore, give riseto a blue color when seen by reflected lierht, just as the thiekness of a soap bubble gives rise to tiie colors seen in it. Owiog to the fact that the thickness of an ordinary film is many times the wavs-length of a ray of light the colors obtained are said to be remarkably brilliant. Thcy are, moreorer, perfectly '.. and the prints have been exposed both to a powerful electric are light and tn bri fht daylight without any i of f ;d ing. It is also found that if the prints are vicwed by transmitted in place of rsilectcd light each color is replaccd by its eomplem.'ntary one