"Talbot did not patent my valuable fixer. Here I had the advantage of having published my use of hyposulphite of soda, which Mr. Hodgson made for me in 1837, when London did not contain an ounce of it for sale. The early operators had no fixer; that was _their fix_; and, so far as any record exists, they got no further in this direction than 'imagining some experiments on the subject!' I tried ammonia, but it acted too energetically on the picture itself to be available for the purpose. It led me, however, to the ammonia nitrate process of printing positives, a description of which process (though patented by Talbot in 1843) I sent to a photographic brother in 1839, and a quotation from my letter of that date has already appeared in one of my communications to _Notes and Queries_. On examining Brande's Chemistry, under the hope of still finding the desired solvent which should have a greater affinity for the simple silver compound on the uncoloured part of the picture than for the portion blackened by light, I happened to see it stated, on Sir John Herschel's authority, that hyposulphite of soda dissolves chloride of silver. I need not now say that I used this fixer with success. The world, however, would not have been long without it, for, when Sir John himself became a photographer in the following year, he first of all used hyposulphite of ammonia, and then permanently fell back upon the properties of his other compound. Two of my solar microscope negatives, taken in 1837, and exhibited with several others by Mr. Brayley in 1839 as illustrations of my letter and of his lecture at the London Institution, are now in the possession of the London Photographic Society. They are, no doubt, the earliest examples of the agency of two chemical compounds which will be co-existent with photography itself, viz., gallate of silver and hyposulphite of soda, and my use of them, as above described, will sanction my claim to be the first to take paper pictures rapidly, and to fix them permanently. "Such is a short account of my contribution to this interesting branch of science, and, in the pleasure of the discovery, I have a sufficient reward."