CELESTIAL CHEMISTIIY. 



The importance and marvellous character of the discoveries effected during the 

 past year through the new method of" spectrum analysis," warrants their classifi- 

 cation into an independent section in this yearly recor.1 of seieutilic discovery. 



THE MOST RECENT DISCOVERIES BY SPECTRUM ANALYSIS. 



In the previous volumes of the Annual of Scientific Discovery, 

 (1862 ; '03 ; '64 ;) the progress of discovery effected through the beau- 

 tiful process of "spectrum analysis 11 has been detailed at considera- 

 ble length ; and in the volume for 1864, particular mention was made 

 of the results arrived at by Messrs Huggins and Miller of England, 

 in their examination of the sun and certain of the fixed stars. These 

 two gentlemen, have, during the past year, continued their researches, 

 and have announced a series of discoveries of the most extraordinary 

 and interesting character. These discoveries may be classified under 

 three heads, viz : Those relating to the Planetary Spectra ; to the 

 Fixed Stars ; and to the Spectra of Nebulas.* 



The apparatus used by Messrs. Huggins and Miller is of the most 

 ingenious and beautiful character. Without going into a detailed 

 description of it, it may be sufficient to say, that, in order to concen- 

 trate the light of such faint bodies as the stars, before admitting it 

 into a prism, or series of prisms for refraction and dispersion in order 

 to form a spectrum, a telescope of large size is indispensable to the 

 observer. The telescope used by Messrs. Huggins and Miller has an 

 object-glass of eight inches aperture and ten feet focal length, and 

 was originally made by Mr. Alvan Clark of Massachusetts, for the Rev. 

 W. Dawes, the well-known English astronomer. Furthermore, as a 

 star forms only a point of light in the focus of an object-glass, this 

 light would be drawn out by the prisms with a fine line of colored 

 light, without sufficient breadth for affording observation of the fine 

 lines crossing it. Some method of expanding this point of light (and 

 in one direction only, so as to prevent unnecessary loss of light) to 

 give the required breadth to the spectrum is therefore needed, and 

 this has been effected by the employment of a cylindrical lens ; and 

 the light thus spread out, is then resolved by the highly refracting 

 prisms, into a spectral image. It has been also ascertained, that the 

 adaptation of a small prism to the slit of the spectroscope enables the 

 vspectrum of one substance to be superposed over that of another sub- 

 stance ; but when it was desired, as it was absolutely necessary to do, 

 to compare the spectrum afforded by the reflected light of the planet 



* For the detail of these discoveries, we are mainly indebted to a report published 

 in the Intellectual Observer, London, January, 1805, by Thomas W. Burr, F. R. 

 A. S. with the concurrence of Mr. Huggins. 



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