Scientific American 22, 24.11.1860
The following facts in regard to Way's electric light, which is now attracting so much attention, we find in the London Photographic News:-
A bried account of Professor Way's electric light was given in recent number of the Photographic News (No. 106, page 230), and from the interest which was created by our notes on the subject we think our readers will be pleased to know the results of some investigations on the subject of the mercury light in its relation to color and photographic effect, which Mr. Crookes has recently made known. The light which is obtained from the fluid mercury poles in Professor Way's arrangement is of a very peculiar character, unlike the ordinary electric light, which, as our readers are aware, is produced between two carbon poles, and contains at least as many different colored rays as sunlight itself, the mercurial light consists of only six definite homogeneous colors, each occupying a particular space in the solar spectrum, and having wide black interwal between them. The carbon electric light will thus illuminate any pbject with the exact color which it is best able to reflect; but with the mercury light it is Hobson's choice, the object must either reflect one of the six colors evolved by the light, or it must remain in darkness. The colors are as follows: - First, at the lowest end of the spectrum comes a brick red tint, next to this is a strong yellowish orange, then two emerald green colors nearly touching; after these, and at some distance off, is a rich ultramarine blue, and lastly a violet. So far relates to color, but the rays evolved from the luminous mercury do not end here. Beyond the violet is another intensely energetic ray, but which, to be rendered apparent to the limited range of the eye, must be received upon some dfluorescent screen, such as a piece of paper washed over with a solution of sulphate of quinine, or allowed to fall on a sensitive collodion plate. This latter surface makes known to us some other interesting properties of this light. Not only will this invisible ray impress itself strongly upon the plate, but the last two visible colors, viz.m the rich ultramarine blue and the violet are also seen to rival it in photographic action. If (as has been done by Mr. Crookes) a more complicated arrangement be employed, and the light be decomposed and refracted into its component parts and thrown upon the collodion plate without having passed through glass at all, as may be effected by having the prisms and lenses cut from pure rock crystal, further remarkable results are obtained. Beyond this one invisible chemical ray are seen others equally energetic in their actinic power, and mounting higher and higher into the almost unknown regions of this invisible and mysterious part of the spectrum. The mercurial electric light thus appears to be almost unique in its properties, unlike other artificial lights it is pre-eminently distinguished by the intensity and number of its photographic rays, and although in its present state it will scarcely do for private or general purposes of house illumination, there is no reason why it may not become at once available for photographers. The reasons which will prevent it coming at present into general use are obvious from the above. Let any one imagine an assembly being illuminated with a light which is deficient in 94 per cent of those colored rays which are usually met with in sunlight. Only those colors would be visible which were capable of reflecting the identical ray of the spectrum contained in the mercury light, and everything else, of whatever color it might be by daylight, would be totally black. Instead of having a thousand varied hues and tints to rest the eye upon, we should be limited to the six colors named above, and their combinations; and any one who has considered for a moment how intimately any sstem of internal illumination depends for its success upon the dacility of reflecting and showing up varieties of colors and tints, will at once see that a source of light, however brilliant and valuable, could scarcely meet with private or public approbation if it were so signally deficient in discrimination as to transform the warm glow of health on a fair girl's cheek, to the ghastly and cadavorous hue of death. Whist raising these objections agains the mercurial light for private or domestic purposes of illumination, we cannot but think that for photographic purposes it would be invaluable. Containing as it does so many and intense photographic rays, and having such advantages over the ordinary form of electric lamp, we wait with impatience the further developments and improvements which will be necessary before it can be brought before the public.