E. S. Drone

“ Gaffield, "or change of color or shade by sunlight being established, must we not transfer some of our praise for the old artists in glass to the wonderful pencil of the brightest luminary of the heavens, which, during the centuries, has noiselessly but unceasingly been at work, deepening and mellowing the colors of all the windows of the venerable cathedrals of the world? We do not see to-day the glass as it was when it came from the artist's studio or the glass-factory. The dust of ages has accumulated upon its surface, the corroding tooth of Time has eaten into it ”

“ Prominent among other interesting facts shown by these experiments is the varying effect of sunlight during each season, and each month of the year. The comparative actinic power of the rays during each month is shown, at the end of the year, by the comparative depth of yellow or purple color produced. The actinic effect increases from January to July, and decreases after the latter month; the greatest effect is observed in the summer, and the least in winter; in the spring and autumn it is about equal, being midway between that of winter and summer. ”

“ Of the colored glasses it was found that blue transmitted the most, purple less, and red and orange the least; which shows the propriety of the preference given by photographers to blue glass for skylights, because it transmits the blue rays, which exert the most active power. Mr. Gaffield's observations have not been confined to the glasses exposed on his own roof and window-sills; but he has been earnest in collecting, from various sources, specimens of window-glass that have been exposed for greatly-varying periods. ”