Secondly, I prefer making the iodide of silver in the way which I have described.
Thirdly, Soft water is better for washing the iodized paper; if, however, spring water be made use of, warm water should be added, to raise it to a temperature of sixty degrees. I think that sulphate or bicarbonate of lime would be injurious, but I cannot speak with any certainty in this respect, or to muriate of soda.
Fourthly, The iodized paper should keep good for a year, or longer; but it is always safer not to make more than is likely to be used during the season.
Fifthly, If I am going out for a day, I generally excite the paper either the last thing the night before, or early the following morning, and develope them the same night; but with care the paper will keep for two or three days (if the weather is not hot) before exposure, but of course it is always better to use it during the same day.
Wm. J. Newton.
6. Argyle Street.
Talc for Collodion Pictures.—Should any of your photographic friends wish to transmit collodion pictures through the post, I would suggest that thin plates of talc be used instead of glass for supporting the film; I find this substance well suited to the purpose. One of the many advantages of its use (though I fear not to be appreciated by your archæological and antiquarian section) is, that portraits, &c., taken upon talc can be cut to any shape with the greatest ease, shall I say suitable for a locket or brooch?
W. P.
Headingley, Leeds.