326 PROCEEDINGS OF THE AMERICAN ACADEMY 



Spectra which are comparable in size to the spectrum of the Sun as it 

 was known to Frauenhofer. The method of the latter consisted in 

 placing a prism of small refracting angle directly in front of the ob- 

 jective of the telescope, and in dispensing with the collimator. A 

 cylindrical lens was employed to spread out the more or less linear 

 spectra thus obtained. Frauenhofer's objective was about four inches 

 in diameter, and the prism was a small one, suitable for this aperture. 

 Professor Pickering employed a lens of eight inches in aperture, and 

 a prism eight inches square, with a refracting angle of thirteen de- 

 grees. In some cases, three and four prisms were employed. The 

 spectra were enlarged by means of a cylindrical lens, and also by 

 giving the negative a motion in the direction of the lines upon the 

 negative. 



Professor Pickering has also employed spectrum analysis to the 

 determination of the motions of the components of variable stars. 

 He has discovered a large number of nebulae and stars with singular 

 spectra. A catalogue of stars with various types of spectra is now 

 under way. The first volume of this catalogue has already beeu pub- 

 lished. This work on stellar spectra is greatly in advance of any- 

 thing else on this subject which lias been done, and is worthy, in the 

 opinion of the committee, of the award of the Rumford Medals. 



For the Committee, 



J. Lovering, Chairman. 



This report was accepted by the Academy, and it was 

 Voted, That the Rumford Medal be awarded to Professor 

 Edward C. Pickering. 



On the motion of Professor Trowbridge, it was 

 Voted, To appropriate from the income of the Rumford 

 Fund one hundred dollars ($100) to Professor E. H. Hall 

 for an investigation of the conduction of heat in the walls of 

 the cylinder of the steam-engine, and two hundred and fifty 

 dollars ($250) to Professor B. O. Peirce for an investigation 

 of the conduction of heat in the interior of solid bodies. 



The following appropriations from the general fund were 

 voted : — 



For publications $1,500 



For the library 1,200 



For the expenses of meetings . . . 200 



