NATURAL PHILOSOPHY. 157 



PANORAMIC STEREOSCOPES. 







A patent has been recently taken out in England for a compound stereoscope, 

 in which general or panoramic views of boulevards, streets, banks of rivers, 

 and coast lines, monuments, sea views, etc., may be displayed by means of the 

 gradual unrolling of one or more endless slides or bands carrying pictures. 

 The distinctive feature of this invention is the adaptation to stereoscopes of 

 one or more symmetrical, independent, movable, endless bands, on which are 

 right and left hand halves, or corresponding parts of a stereoscopic pano- 

 rama, or succession of pictures. The following is the construction of the in- 

 strument : The top thereof consists, as usual, of two lenses or eye-glasses, 

 and the bottom thereof is mounted on a box containing rollers, on which are 

 wound the before-mentioned endless slides or bands, on which are printed, 

 pasted, or otherwise appropriately attached, the views or pictures in panora- 

 mic succession ; also a train of wheelwork for setting the aforesaid bands in 

 motion. The aforesaid bands and corresponding parts of the pictures thereon 

 are brought under their respective eye-glasses upon a flat stage or platform 

 over which the bands pass, so that, when set in motion, a panoramic stereos- 

 copic view or picture is thus obtained. The description of the instrument is 

 not very clear, we fear, to those who are not acquainted with the effect. We 

 have, however, seen a similar instrument, and can assure our readers that 

 nothing can surpass the beauty and interest of a beautiful stereoscopic pano- 

 rama moving before the eyes of the spectator. Photographic News. 



PERSISTENT ACTIVITY OF LIGHT. 



M. Moigno, editor of the Cosmos, communicates the following interesting 

 facts in relation to the above subject: 



M. Niepce St. Victor exhibited to us a large tin tube, closed hermetically, 

 and rendered inaccessible to all external agencies, except variations of tem- 

 perature. He opened the tube in our presence, exposed, without unrolling it, 

 a sheet of paper prepared with tartaric acid and isolated, which he had 

 enclosed in the tube nearly a year before, poured on this sheet a few drops of 

 nitrate of silver, and showed us that the nitrate was almost immediately 

 blackened, exactly as it would have been in a strong light. It was impossible 

 not to attribute this instantaneous effect to the persistent action of the light 

 absorbed, a year ago, by the paper soaked in tartaric acid. If the experiment 

 was more successful this time, although kept for a longer peiiod, it was 

 because of the much more perfect closure of the tube; and that which 

 happened after a year would certainly happen after five or six years. 



Again, M. Busk has established the following fact : Plunge a sheet of paper 

 into a solution of a properly chosen acid, organic or inorganic, for example, 

 acetic or tartaric acid; dry it; render it sensitive by the bath of nitrate of 

 silver, and dry it again; place it in contact with the drawing which it is de- 

 sired to reproduce for a half hour or more ; then expose the paper to the sun's 

 rays, and a negative image of the drawing will be seen, which may be fixed 

 by washing with common water. It is not even necessary that the exposure 

 to the light should take place at once; the paper may be preserved for several 

 days, between two sheets of white paper, without losing its property of 

 developing the latent image under the influence of the sun's rays. What is 

 more difficult to explain, is, that there is no necessity of insolating or exposing 

 to light the original picture. 



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