342 



Messrs. Huggins and Miller on Spectra [May 26, 



Such are the points which I propose to examine in the next place ; in 

 the mean time the observations I have just alluded to are a proof that 

 bodies can absorb a certain amount of heat not indicated by the thermo- 

 meter (vphich becomes latent)^ and that this is effected without the body 

 undergoing a change of state ; secondly, that they slowly part with this 

 heat again until they have acquired their original densities ; thirdly, so 

 many different substances being affected by a change of density when 

 melted or simply heated to redness and allowed to cool, it is probable this 

 property will be found to belong, more or less, to all substances without 

 exception. 



II. On the Spectra of some of the Fixed Stars/' By W. Hug. 

 GINS, E.R.A.S., and William A. Miller, M.D., LL.D., Trea- 

 surer & y.P.R.S., Professor of Chemistry, King's College, London. 

 Keceived April 28, 1864. 



(Abstract.) 



After a few introductory remarks, the authors describe the apparatus 

 which they employ, and their general method of observing the spectra of 

 the fixed stars and planets. The spectroscope contrived for these inqui- 

 ries was attached to the eye end of a refracting telescope of 10 feet focal 

 length, vath. an 8-inch achromatic object-glass, the whole mounted equa- 

 torially and carried by a clock-movement. In the construction of the 

 spectroscope, a plano-convex cylindrical lens, of 14 inches focal length, was 

 employed to convert the image of the star into a narrow line of light, 

 which was made to fall upon a very fine slit, behind which was placed an 

 achromatic collimating lens. The dispersing portion of the arrangement 

 consisted of two dense flint-glass prisms ; and the spectrum was viewed 

 through a small achromatic telescope with a magnifying power of between 

 5 and 6 diameters. Angular measures of the different parts of the spec- 

 trum were obtained by means of a micrometric screw, by which the posi- 

 tion of the small telescope was regulated. A reflecting prism was placed 

 over one half of the slit of the spectroscope, and by means of a mirror, 

 suitably adjusted, the spectra of comparison were viewed simultaneously 

 with the stellar spectra. This light was usually obtained from the in- 

 duction spark taken between electrodes of different metals. The dispersive 

 power of the apparatus was suflacient to enable the observer to see the line 

 Ni of Kirchhoff between the two solar lines D ; and the three constituents 

 of the magnesium group at h are divided still more evidently *. Minute 



considerable time. The increase of density of Gadolinite and the decrease of density of 

 Samarskite by the action of heat are accompanied by a vivid emission of light, as mentioned 

 in my work on ' Phosphorescence' &c., pp. 31 and 32, where H. Rose's ingenious expe- 

 riment is described. 



* Each unit of the scale adopted was about equal to ^gVo^h of the distance between 

 A and H in the solar spectrum. The measures on different occasions of the same line 

 rarely differed by one of these units, and were often identical. 



