146 ANNUAL OF SCIENTIFIC DISCOVERY. 



ing from twelve to twenty-four hours, and the proof is of admirable trans- 

 parence, the paper also keeping all its whiteness. Comptes Rendus. 



Photo-Lithoyraphy. This name lias been applied by the discoverers, 

 Messrs. Cutting & Bradford, of Boston, to a new and beautiful application of 

 the photographic art, which is evidently destined to revolutionize, in a great 

 measure, the ordinary processes of lithography. The requisites for the pro- 

 duction of the effect are, in the first instance, a well-ground lithographic stone, 

 and a glass negative photograph. The stone, by a peculiar treatment, which 

 is really the discovery itself, and is yet a secret, is prepared in a few minutes 

 to receive the photographic impression, through the glass negative, by expo- 

 sure to sun-light. The stone-picture can then be washed, inked, and any 

 number of photo-lithographs printed from it upon paper, by means of the 

 usual lithographic press. Images magnified by the microscope, and thrown by 

 means of the camera upon a prepared stone surface, are depicted with wonder- 

 ful accuracy. The value of this discovery, as applied merely to the illustra- 

 tion of books, especially scientific treatises, is obvious. 



The French Academy have recently received some interesting memoirs on 

 subjects connected with photography. In the camera obscura, which is 

 usually employed in photographic operations, the objects daguerrcotyped are 

 traced by the sun on a plane surface, whose extent (being necessarily re- 

 strained) corresponds to a field of vision which cannot well cover more than 

 thirty or thirty-five degrees of angular space. So, too, in the art of draw- 

 ing, when the draughtsman Avould represent a scene on the plane, he takes 

 care to restrict it to the same limits, as they include all the objects our eye is 

 able to take in at the same time, without changing its direction. But if he 

 desires to depict a larger portion, or rather all the objects which may be seen 

 in every different direction from a given station, it is evident that instead of 

 taking a plane surface, he must take the interior surface of a cylinder; for the 

 observer, being placed upon the axis, will discover a suitable clement, on 

 whatever side he may look, for tracing the object supposed to be placed in 

 the same direction. This sort of cylindrical picture, developed in a circular 

 manner around the spectator, is called a panorama. In 1845, a photographer 

 named Martens, published a method for obtaining, upon the daguerreotype 

 plate, and in one single operation, a demi-panorama of exterior views. The 

 plate was curved in a demi-cylindrical form around the optical centre of the 

 objective, which being placed on a vertical pivot, was directed in succession 

 to the different points of the horizon, carrying along with it a diaphragm, 

 having an aperture with vertical edges ; in this wqy the different portions of 

 the plate were affected in succession, so that when once the proof Avas com- 

 pleted, it represented all objects visible within an angular field of 180 degrees. 

 The scenes obtained in this way by M. Martens, were beautiful little pano- 

 ramas; but the objects were represented in it in an inverse order to that they 

 occupied in nature, and, unfortunately, the geometrical combination on which 

 the method was founded, prevented the operator from restoring the objects 

 to their original position. Had the operator attempted to place a reversing 

 mirror before the objective, he would instantly have discovered that, during 

 the evolution of the optical system, the clouds would have assumed a relative 

 motion on the plate, which would have rendered it impossible to take a 

 daguerreotype. Besides, as more daguerreotypes are taken on glass than on 

 metal at the present day, and as it is inconvenient to bend a plate of glass, 

 M. Martens' ingenious method gradually fell out of use. We now have a 



