The Science record; a compendium of scientific progress and discovery . ar from having its maxi-mum sensitiveness, as is shown by the following experi-ment, which is of no small interest to photographers : Itook five dry collodion plates, prepared by what is knownas the tannin process ; and having made a pile of them, Icaused the rays of a gas-flame to pass through them all atthe same time. On developing, it was found that the first 236 SCIENCE RECORD. plate was strongly impressed ; and the second, which hadbeen behind it, apparently quite as much. Even the fifthwas considerably stained. From


The Science record; a compendium of scientific progress and discovery . ar from having its maxi-mum sensitiveness, as is shown by the following experi-ment, which is of no small interest to photographers : Itook five dry collodion plates, prepared by what is knownas the tannin process ; and having made a pile of them, Icaused the rays of a gas-flame to pass through them all atthe same time. On developing, it was found that the first 236 SCIENCE RECORD. plate was strongly impressed ; and the second, which hadbeen behind it, apparently quite as much. Even the fifthwas considerably stained. From this it follows that thecollodion-film, as ordinarily used, absorbs only a frac-tional part of the rays that can affect it. Could it bemade to absorb the whole, its sensitiveness would bs cor-respondingly increased. NEW STEREOSCOPE FOR LARGE PICTURES. By D. WiNSTANLEY.—In the accompanying diagram, Ihave attempted to indicate the construction of an instru-ment available for pictures of large size. The two halvesof each stereogram are to be mounted on pieces of card-. board, joined together by leather, cloth, or other flexiblematerial, so that the whole may be shut up like a book,with the pictures face to face. Let L and R indicate respectively the positions of theleft and right eyes of the observer, and the lines, A B andB C, the boards or frames upon which the folio picturesrest. The perpendicular pencils of light from the centreof each picture now reach the eye-pieces in converging ELECTRICITY, LIGHT, HEAT, SOUND. 237 lines, which, by transmission through the prisms, may berendered parallel or divergent to suit the particular theoryof binocular vision approved of by the constructor of theinstrument. I may observe that parallelism is the ideawhich accords best with my own apprehension of the sub-ject. After transmission through the prisms, the rays arefinally passed through suitable magnifying lenses, whosecentres, I apprehend, may be employed for the purposesof vision. The e


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Keywords: ., bookcentury1800, bookdecade1870, booksubje, booksubjecttechnology