130 ANNUAL OF SCIENTIFIC DISCOVERY. 



it can, however, be rendered active by the addition of a few drops of 

 muriatic acid. The purer the silver employed, the more perfect is tho 

 impression, and the more intense the colors. 



The plate being very highly polished, which is best effected by 

 Tripoli powder and ammonia, is connected with the battery, and then 

 plunged into the bath, and kept there for some minutes ; it is then 

 taken from the bath, washed in a large quantity of water, and dried 

 over a spirit-lamp. The surface thus produced is a dull neutral tint, 

 often almost black, and, upon exposing it to the light, the colors are 

 produced by removing the blackness ; the surface is, in fact, eaten out in 

 colors. The sensibility of the plate appears to be increased by the 

 action of heat, and when brought by the spirit-lamp to the cerise red 

 color, it is in its most sensitive state. At present, however, the plate 

 cannot be rendered very sensitive, two or three hours being required to 

 produce a decided effect in the camera-obscura. It is, however, 

 already found that the fluoride of sodium will very much accelerate the 

 operation. 



The fixation of the colored image is, however, still a point of con- 

 siderable difficulty, and, although a certain degree of permanence has 

 been recovered, the colors fade out by exposure and eventually pass away. 

 A kind of lacquer appears to have been applied to the plates we have 

 seen, and ordinary diffused light does not seem to produce much change 

 upon them. 



Such is an outline of the researches of M. Niepce, as communicated 

 by him to the Academy of Sciences. He is still zealously occupied in 

 the inquiry, and will soon, we trust, be enabled to communicate some 

 yet more important results. The problem is, however, solved ; we can 

 produce pictures by the agency of the solar beam in natural colors ; 

 that principle which gives to the exterior creation the charm of color, 

 will so regulate the chemical agency of the actinic power with which 

 it is associated, that, on properly prepared surfaces, the images are 

 painted in their native hues. 



The following description of the pictures executed by M. Niepce, and 

 exhibited in England, is from the London Athengeuui : " The three 

 heliochromes now in London are copies of colored engravings, repre- 

 senting, the one a female dancer, the others male figures in fancy cos- 

 tumes ; every color of the original being most faithfully impressed on 

 the prepared silver tablet. The female figure has a red silk dress, with 

 purple trimming and white lace. The flesh tints, the red, the purple, 

 and the white, are well preserved in the cop}'-. One of the male figures 

 is remarkable for the delicacy of its delineation: here blue, red, 

 white and pink are perfectly impressed. The third picture is injured 

 in some parts, but is, from the number of colors which it contains, tho 

 most remarkable of all. Red, blue, yellow, green, and white are dis- 

 tinctly marked ; and the intensity of the yellow is very striking." 



The Hillotype. Much has been said, during the past year, respecting 

 a discovery claimed by Rev. Mr. Hill, of Greene county, N. Y., of pro- 

 ducing daguerreotypes with the natural colors of the object represented. 

 The statements made by Mr. Hill and friends, not being confirmed by 

 anything tangible, the New York Daguerrian Association appointed a 



