176 ANNUAL OF SCIENTIFIC DISCOVEEY. 



presented were from 2 to 4J- inches. For taking the impressions, the heliostat 

 was regulated in such a manner as that the telescope gradually followed the 

 moon's right ascension the hour circle and the circle of declination having both 

 been stopped, which maintained the moon as perfectly as possible in the same 

 place as she appeared hi the searcher, by means of the screw which gives the 

 instrument its smooth motion in right ascension and declination ; the telescope 

 being 4 feet diameter. Two of the images taken, one before the other, from 

 the full moon, when combined together in the stereoscope, gave a sensation of 

 well-detached relief; we may say a semi-globe, with the half transparent. 

 The enlarged views have been projected on a screen by the magic-lantern, and 

 are much admired. Humphrey's Daguerrean Journal. 



Colored Plwtoyrapks obtained by single exposure to light. At a recent meet- 

 ing of the Societe. de Photographic, Paris, M. Beauregard exhibited a number 

 of colored photographs, of which the following description was given. The 

 prints form a series of colored images, some uniformly blue, yellow, or rose ; 

 others possessing the different tints, in relation to natural colors upon the same 

 sheet of paper. Among the latter, one represented the head of a woman 

 draped with a transparent vail, and bearing a basket of foliage. The flesh is 

 of the natural color, the vail violet, and the foliage green. Another is a por- 

 trait of a woman, whose face and hands are flesh-colored, the eyes blue, the 

 hair light-brown, the dress green, and the collar and sleeves white. Lastly, a 

 portrait of a child, which, besides the flesh-color of the face, hands, and legs, 

 presents a dress striped with green and yellow, black boots, white linen, and 

 a couch of black wood with chamois cushion. There is also a little landscape, 

 with the effect of sunset, tinted with different colors. 



M. de Beauregard set out from the long-known fact that there exist salts 

 which are colored in a different manner by light; that this diversity of color- 

 ation is manifested not only in relation to the special nature of each of the 

 salts, but also from the same salt, in proportion to the duration of the action 

 of light; or, in other words, to its intensity. This point being settled, M. de 

 Beauregard asked whether, by combining several of these salts, either directly 

 in the same bath, or on the paper itself, by means of successive immersions in 

 baths of different compositions (such, for example, as photographers at present 

 use for producing iodide of silver), it would be possible to obtain papers which, 

 when exposed at once to the action of light, would manifest the different 

 colors, and these more or less deep in tint, according to the nature of the salts 

 and the intensities of the luminous rays. 



It is important to state here that the process of M. de Beauregard does not 

 consist in applying colors locally, as in the printing or dyeing of stuffs. The 

 colors which he obtains are produced in the printing-frame itself, by one and 

 the same impression of light, except merely the fixation and final development 

 of the print, as with the hyposulphite baths in the ordinary process. The first 

 idea of M. de Beauregard was simply to study the means of producing photo- 

 graphic prints at a low price, and for this purpose he set to work to find a 

 substitute for the salts of silver. He first tried ferro-cyanide of potassium. 

 This salt it is which, in moderately concentrated aqueous solution, gives the 

 print that uniform blue tint which we see in the various specimens exhib- 



