Being located in a neighbourhood where there is a scarcity of water in the summer months, I lately took advantage of a pool in a running stream, which ran at the bottom of the grounds of a friend, to soak my calotype papers in, subsequent to having brushed them over with the solution of iodide of silver, according to the process recommended by SIR W. NEWTON. One-half of the batch was removed in about two hours and a half, being beautifully clean, and of a nice light primrose colour; and in consequence of an unexpected call and detention longer than I had anticipated, the other half was left floating from two o'clock P.M. until seven or eight in the evening (nearly six hours), when, much to my chagrin, I found on their removal that they had all, more or less, become browned, or, rather, had taken on a dirty, deep, nankeen colour, those that had been first floated being decidedly the worst. I had previously thought that the papers _must_ be left _at least_ two and a half to three hours, a longer period having no other effect than that of softening the papers, or, at most, of allowing some slight portion of the iodide to fall off from their surface, whereas, from the above-described discoloration, an evident decomposition must have commenced, which I am quite at a loss to account for; neither can I conjecture what the chemical change can have been. I have several times before prepared good papers in trays filled with water from the same stream, but from the quantity running in the brook in the spring months, I never before have had the chance of floating them in the stream itself. An explanation of the above difficulty from some obliging and better-informed photographist would be very thankfully received by HENRY H. HELE. Ashburton, Devon. P.S.--The pool of water was well shaded, consequently not a ray of bright sunlight could possibly impinge on the papers while floating. I have always understood that _pure_ iodide of silver was quite insensible to the action of light, or to any other chemical change, as far as the action of atmospheric air was concerned. * * * * * Replies to Minor Queries.