NATURAL PHILOSOPHY. 139 



the combining weights themselves, and may accordingly be estimated 

 with an almost astronomical precision." 



New Instrument for Spectral Analyses. A new instrument for 

 exhibiting the fixed lines in spectra, from different sources, far more 

 simple than that made use of by Messrs. Bunsen and Kirchhoff, 

 has been described by M. Mousson in Poggendorff's Annalen, under 

 the name of the Spectroscope. The apparatus consists essentially of a 

 tube blackened internally, and having at one extremity a plate of 

 metal, with an adjustable slit for the admission of light. The prism is 

 placed at the other extremity of the tube, so that the eye of the ob- 

 server may be brought close to its second refracting surface. ^ The 

 tube is attached to an appropriate stand, so that it may be conveniently 

 directed to the light to be examined ; and the eye of the observer is 

 protected from extraneous light by a small screen of metal attached 

 to the tube. The edges of the slit must be ground perfectly true. 

 This apparatus does not require a darkened chamber or delicate and 

 difficult adjustments. In a communication to Silliman's Journal, July, 

 1861, Prof. Wolcott Gibbs states that it can be obtained in New York 

 city of Mr. Chas. Sacher ; price twenty-five dollars. 



RESEARCHES BY MEANS OF THE PROCESS OF SPECTRUM ANAL- 

 YSIS ON THE CONSTITUTION OF THE SOLAR ATMOS- 

 PHERE. 



M. Kirchhoff, following up the line of investigation described in the 

 foregoing article, has recently applied the process of photo-chemical 

 analysis to the study of the constitution of the sun's luminous envel- 

 loping atmosphere. He maintains, as the result of examinations, that 

 the sun has an ignited gaseous atmosphere, which encloses a core of 

 still higher temperature. If we could see the spectrum of this atmos- 

 phere,we should detect the bright lines which are characteristic of the 

 metals existing in it, and should recognize the metals themselves from 

 these. The more strongly luminous body of the sun does not, how- 

 ever, permit the spectrum of his atmosphere to appear. It inverts 

 this spectrum ; so that instead of the bright lines which the spectrum 

 of the atmosphere alone would exhibit, dark ones make their appear- 

 ance. We see, therefore, only the negative image of the spectrum of 

 the sun's atmosphere. 



In order to study the solar spectrum with the requisite degree of 

 accuracy, Kirchhoff procured from the workshop of Steinheil an ap- 

 paratus consisting essentially of four large flint-glass prisms and two 

 telescopes. 



With this apparatus the spectra are seen in a hitherto unattainable 

 degree of distinctness and purity. It exhibits in the solar spectrum 

 thousands of lines, with such clearness that they are easily distinguished 

 from each other. It is the author's intention to draw the whole 

 spectrum, as seen with his apparatus, and he has already done this for 

 the portion which lies between Fraunhofer's lines D and F. 



This apparatus exhibits the spectrum of an artificial source of light 

 with the same distinctness as the solar spectrum, provided only that 

 the intensity of the light is sufficient. A common gas-flame, in which 

 a metallic compound evaporates, is usually not sufficiently luminous, 



