176 ANNUAL OF SCIENTIFIC DISCOVEEY. 



Doubts respecting Bunsen and Kirchhoff' s Results. The London 

 Photographic News makes the following remarks on the present state 

 of our knowledge respecting " spectrum analysis : " 



The subject is affording grounds for much scientific debate, and 

 the opinion is gradually gaining ground that there are many reasons, 

 experimental as well as theoretical, for concluding that the sweeping 

 explanation of the cause of Fraunhofer's lines given by the German 

 savans, Bunsen and Kirchhoff, is, to say the least, open to great 

 doubts. Prof. Miller, at a late meeting of the London Pharmaceuti- 

 cal Society, urged the necessity of still considering the views of 

 Kirchhoff and Bunsen as theoretical, there being many points which 

 presented anomalous features. Some spectral lines, he said, were 

 due to the incandescent metals, but others undoubtedly belonged to 

 the atmosphere, or to the different gases in which the ignition of the 

 metal took place. The rise of temperature, too, evoked different 

 lines from the same substance. Chloride of lithium, in a Bunsen 

 burner, gives a single crimson ray ; in the hotter flame of hydrogen 

 an additional orange ray appears ; whilst the oxy hydrogen jet, or 

 the voltaic arc, brings out a broad, brilliant blue band in addition : 

 the same takes place with sodium and other metals. Fascinating as 

 the German theory is, it must be remembered that it is still upon 

 trial, and that it does not yet explain the facts known respecting the 

 vapors of hydrogen, mercury, chlorine, bromine, sodium, or nitrogen. 



HELIOCHKOMY. 



M. Niepce de St. Victor has communicated to the French Academy 

 an important step towards the fixation of heliochromic tints, which 

 increases the hope that before long colored objects may be success- 

 fully photographed. He states that he "obtains the heliochromic 

 colors on a film of chloride of silver formed on a metallic plate." In 

 preparing this plate he employs hypochlorite of potash, and he 

 remarks, " This alkaline bath, although very variable in its compo- 

 sition, generally gives fine colors, only the bottom of the image re- 

 mains somewhat dark, and divers causes occasion certain colors to 

 dominate over the rest." Continuing his description, he observes, 

 " It is known that to obtain the colors on a white ground it is neces- 

 sary to heat the plate, before exposing it to the light, until the chlo- 

 ride of silver assumes a rosy tint, or to substitute for the action of heat 

 that of light, in the manner indicated by M. C. Becquerel. I con- 

 ceived the idea of covering the chloride film, before- exposing it to 

 the light, with a layer of a saturated solution of chloride of lead 

 mixed with enough dextrine to form a varnish." He found that the 

 colors were produced with greater brilliancy on a plate thus pre- 

 pared, and after their appearance the plate was heated over a spirit- 

 lamp, not raising the temperature high enough to carbonize the var- 

 nish. " Under the influence of heat, the colors usually grow more 

 intense, especially i the light has influenced the whole thickness of 

 the chloride of silver ; but if otherwise, the blues are turned into 

 violets, and the blacks to reds." The result of the process is, " that 

 the destructive action of light upon the plate is retarded, so that ten 

 or twelve hours are necessary to destroy the color?, which, under 



