558 



REPORT — 1891. 



thus discovered, and those for which the wave-length has been deduced are given 

 in the first column of the table. The wave-lengths of the H and K calcium lines 

 are to be regarded as provisioaal only, as Professor Rowland has not yet published 

 the final values. The other columns contain measures of the lines in the hydrogen 

 series, all reduced to Rowland's scale. 



It -will be seen that the first two lines are in all probability due to calcium ; they 

 are narrow and sharp, and fall at the centres of the dark bands in the solar spectrum-. 

 The next line is as yet unaccounted for, but it does not appear to be a component 

 of the hydrogen line at X3889-14. The line at X3070-11 is marked doubtful, because' 

 it falls very nearlj' at the position of a ghost of li ; everything points, however, to 

 an independent origin, though the agreeu)ent with Ames' hydrogen line at X3970'25 

 i?i far from satisfactory. The remaining four lines are evidently members of the 

 hydrogen series. 



Prominence forms have also been photographed through H and K, the dark 

 shades allowing the use of a very -wide slit. The research is to be continued with 

 improved apparatus. 



5. Report on Researches Relative to the Second Law of Thermodynamics, 

 By Dr. J. Larmou and G. H. Brtan. — See Reports, p. 85. 



G. Note on a Simple Mechanical Representation of Garnot's Recersille Cycle} 

 By G. H. Bryan. 



FRIDAY, AUGUST 21. 



The following Reports and Papers -were read : — • 



1. Interim Report of the Committee on Researches in Electro-optics. 

 See Reports, p. 147. 



2. Note on the Electromagnetic Theory of the Rotation of the Plane of 

 Polarised Light. By Professor A. Gray, M.A., F.R.8.E. 



Sir William Thomson has explained the turning of the plane of polarised light 

 in a magnetic field by supposing the ether to have imbedded in it a large number 



' This note is reproduced in Par. 38 of the Report on the Second Law of Thermo- 

 dynamics by the author. 



