ABSTRACT
The improvements in the mode of production of light for common use are sufficiently new and remarkable to distinguish this century from all the ages that preceded it, but they sink into insignificance when compared with the discoveries which have been made as to the nature of light itself, its effects on various kinds of matter leading to the art of photography, and the complex nature of the solar spectrum leading to spectrum analysis. The fact that certain salts of silver were darkened by exposure to sunlight was known to the alchemists in the sixteenth century, and this observation forms the rudiment from which the whole art has been developed. When such a series of pictures, magnified to life-size, are thrown on a screen, the effect is very striking, and with proper adjustments of light the appearance is deceptively like a real scene passing before the spectators.
