[Illustration: Lomaland Photo. and Engraving Dept. THE CANAL, TROLLHÄTTAN, SWEDEN] [Illustration: Lomaland Photo. and Engraving Dept. HIGH SLUICE AND PALACE OF INDUSTRY, AMSTERDAM, HOLLAND (At Amsterdam a stone arch bridge is called a sluice)] [Illustration: Lomaland Photo. and Engraving Dept. PALACE OF INDUSTRY, AMSTERDAM] And yet there are some eyes which can plainly distinguish the fact that a substance or surface is giving off these powerful rays, invisible to less sensitive eyes. Perhaps this is one of the thousands of little forerunner facts which testify to the increase of sensibility prophesied by H. P. Blavatsky for this present century. Now if a solution of one per cent of sulphate of quinine, one centimeter thick, is used in a glass cell before a lens or plate it may delay the exposure by perhaps six times the normal time, thus showing that of our photographs taken under ordinary conditions on ordinary plates we have been accustomed to accepting as true pictures reproductions of the invisible, although much of that invisible coincides with the visible, since these rays are emitted by so many substances. But a false standard has been established unconsciously in our minds. Where blue skies should be, we are content to see a pure white in a photograph. Where reds and yellows abound we expect altogether too dark a representation, as with grass and green trees. The quinine light-filter (aesculine, extracted from the horse-chestnut, serves as well) absorbs or is largely opaque to these rays and such a filter is much used now with specially sensitized plates to allow the colors to be reproduced in monochrome in truer relation. A yellow filter will also absorb some of the visible blue. The glass of the lens too is responsible for the absorption of a proportion of these rays. By an action not yet understood the dyeing of plates with certain dyes renders the silver in them far more sensitive to the various colors in the green, yellow, and red of the spectrum. Is it not probable that silver has the power of sensing these rays so keenly, while the human eye, for reasons best known to the human mind, has had and lost that power, but may be now beginning to regain it? Such a recovery is not made without strain and natures that can begin to sense these invisible rays must either strengthen and purify themselves to the utmost degree possible or suffer what dry leaves suffer in the flames, a burning out of the particles that are not tuned to withstand the red fire that burns them. Hence the theosophical reason for purity and strength, first, last, and all the time, in preparation for the burning fiery flames of added sensitiveness which come and have come quite soon enough for us to prepare against rather than seek.