154 ANNUAL OF SCIENTIFIC DISCOVERY. 



in the eye tlmt actually receives it, or may transpose it seemingly to the other, 

 according to the par.icular conditions of the observation. Silliman's Journal. 



NEW APPLICATIONS OF PHOTOGRAPHY. 



Sir Henry James, director of the Ordnance Survey of Great Britain, states, 

 that liy means of the application of photography to the reduction of maps 

 in the Ordnance Survey office a saving of at least 35,000 has been effected. 

 Formerly the reduction had been effected by the pentagraph, when the 

 accuracy depended on the skill of the operator; now, by merely fixing a 

 camera before a plan, it could be reduced to any scale desired, by an opera- 

 tion of a few minutes' duration, and with the greatest accuracy. The scales 

 of the maps were ten and a half feet to the mile, twenty-five inches to the 

 mile, six inches to the mile, and one inch to the mile. Maps could be 

 reduced from the large scale to all the smaller ones by photography, except 

 to the scale of one inch to the mile. Here it was found that photography 

 was rather too accurate. The photograph thus reduced was found to be too 

 much covered with details, so that they still had to employ the pentagraph 

 in the last operation. The photographs of the maps, once taken, are trans- 

 ferred to a copper or zinc plate by a new process, called " photo-zincogra- 

 phy," which is substantially as follows : Instead of printing the negative on 

 ordinary printing paper, they employed tracing paper, washed over with a 

 saturated solution of bi-chromate of potash and gum-water, and exposed to 

 the action of light. This rendered the bi-chromate insoluble in water. The 

 print was then placed face downwards on a metal plate, covered with litho- 

 graphic ink. It was then washed to remove the portion not acted on by 

 light, by dissolving away the bi-chromate of potash, when the printing was 

 left, of a light brown color, in lithographic ink. This could be transferred 

 to a copper plate, as a guide to the engraver, by placing it face downwards 

 and burning it in; or, for zincographic purposes, by burnishing it down on 

 a zinc plate and merely inking the plate with ordinary ink. 



Application of Photography to the Ornamentation of Porcelain. A patent 

 has been recently granted in England to John Wyard, for the production of 

 photographic images on plates of glass and porcelain, in such a way as to 

 enable them to be permanently fixed by being burnt in with ceramic colors. 

 The details of the process, which are of too tecbjnical a character to warrant 

 insertion in this connection, are made public, and seem to promise a large 

 measure of success. 



On the Employment of Photography for the Determination of the Path and 

 Velocities of Shooting Stars. Professor J. H. Lane, in a communication to 

 Silliman's Journal (July, 1860), suggests the employment of photography 

 for the accurate determination of the path and velocity of a shooting star, 

 with u view to the determination of its orbit. The general plan proposed for 

 adoption by Prof. L. is as follows: In the first place, simple exposure of a 

 highly sensitive photographic plate in a camera, at a given station, would 

 give the apparent track of a meteor as seen by the observer at that station, 

 and a pair of such records, made in two cameras at two stations, would give 

 the tra-k in absolute space. In the second place, if one of the two cameras 

 were furnished with a mechanism by which equidistant points of time should 

 be marked upon the track made in that camera, these points could be referred 

 to the real path in space, and if both cameras were in like manner furnished, 

 the two records would, to that extent, be a check upon each other, and serve 



