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AFTER the article by Dr. W. J. S. Lockyer on the disappearance of photographic images (p. 278) and other references that have been made to this subject, there is no need to dilate upon the importance of the preservation of the vast number of photographic records now being produced in our observatories and laboratories. I would, however, venture to express surprise that the fact established by Dr. Isaac Roberts as to the want of permanence of a silver photographic image appears to have been unexpected, bearing in mind the general procedure that appears to be the rule in the production of such photographs.

The Preservation of Photographic Records