The solution of Pyrogallic Acid may be used of the ordinary strength, with a full dose of Acetic Acid. Only a faint image comes out at first, but on pouring over the plate a fresh portion of the developer with two or three drops of the Nitrate Bath added to each fluid drachm, it may be intensified to any extent. Fix with Hyposulphite of Soda, and wash in the usual way. When the process fails, from heat of the weather or other causes, the image will probably be feeble and red by transmitted light, and the shadows defective and misty. This is especially likely to happen when the Nitrate Bath is very old and contains much Acetate of Silver; or when the same portion of Honey is used more than once, and has undergone partial decomposition by the action of the Nitrate of Silver. The use of _pure_ Honey, free from mouldiness and fermentation, will, _in cool weather_, almost certainly ensure success. _A modification of the process when the plates are to be kept over four hours._--In this case the whole, or the greater part of the Nitrate of Silver must be removed before applying the preservative agent. Wash the sensitive plate in water in the manner described for the Oxymel process in the next page. Then apply the syrup as before, using it as thick as possible. Honeyed plates, free from Nitrate of Silver, may commonly be kept for five or six days; often much longer. Dr. Mansell, who has employed this process with great success, speaks of _temperature_ as a point to be attended to. In hot weather the same length of keeping properties will not be attained. _Use of Oxymel for preserving Collodion plates._--The principal difficulty in the employment of Honey in Photography, is its disposition to ferment, or to become mouldy. Fermentation occurs most readily in a dilute solution, and will be obviated by using the syrup as thick and free from water as possible. Mr. Llewellyn employs "Oxymel," which is a mixture of Honey and Vinegar, as a preservative agent. This substance will keep even in dilute solution for a long time without decomposition; and, being very readily removed from the plates, does not interfere with the development of the image. The preparation of Oxymel is described in the Vocabulary, Part III.; it must be diluted with three or four parts of water, and filtered. Certain facts to which attention has been lately drawn by Dr. Norris and Mr. Barnes in working with dry Collodion, may be advantageously borne in mind when using Oxymel; the preservative solution of which is employed in so dilute a state that the process resembles to a great extent a dry Collodion process. The observations above referred to relate to the quality of the Collodion best adapted for the purpose, and will be found at page 298, to which the reader is referred.