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is at once developed. At first it most commonly happens that 

 the whole picture is sooty or dingy to such a degree that it is con- 

 demned as spoiled ; but on keeping it between the leaves of a book, 

 especially in a moist atmosphere, by extremely slow degrees this 

 dinginess disappears, and the picture disengages itself with con- 

 tinually increasing sharpness and clearness, and acquires the exact 

 effect of a copper-plate engraving on a paper more or less tinted 

 with pale yellow. I ought to observe, that the best and most 

 uniform specimens which I have procured, have been on paper 

 previously washed with certain preparations of uric acid, which is 

 a very remarkable and powerful photographic element. The' 

 intensity of the original negative picture is no criterion of what 

 may be expected in the positive. It is from the production, by one 

 and the same action of the light, of either a positive or a negative 

 picture, according to the subsequent manipulations, that I have 

 designated the process thus generally sketched out, by the term 

 amphitype, a name suggested by Mr. Talbot, to whom I communi- 

 cated this singular result ;^ and to this process, or class of processes, 

 (which I cannot doubt when pursued will lead to some very beautiful 

 results,) T propose to restrict the name in question, though it applies 

 even more appropriately to the following exceedingly curious and 

 remarkable one, in which silver is concerned. At the last meeting 

 I announced a mode of producing, by means of a solution of silver, 

 in conjunction with ferro -tartar ic acid, a dormant picture brought 

 out into a forcible negative impression by the breath or moist air. 

 The solution then described, and which had, at that time, been 

 prepared some weeks, I may here incidentally remark, has retained 

 its limpidity and photographic properties quite unimpaired during 

 the whole year since elapsed, and is now as sensitive as ever, a 

 property of no small value. Now, when a picture (for example an 

 impression from an engraving) is taken on paper washed with this 

 solution, it shows no sign of a picture on its back, whether that on 

 its face be developed or not ; but if, while the actinic influence is 

 still fresh upon the face, (i. e. as soon as it is removed from the 

 light,) the bafk be exposed for a very few seconds to the sunshine, 

 and then removed to a gloomy place, a positive picture, the exact 

 complement of the negative one on the other side> though wanting 

 of course in sharpness if the paper be thick, slowly and gradually 

 makes its appearance there, and in half an hour or an hour acquires 

 a considerable intensity. I ought to mention that the " Ferro-tar- 

 taric acid " in question is prepared by precipitating the ferro-tar- 



