Royal Institution. 147 



themes contained in the sets will be found to consist of purely 

 monomial, binomial, and trinomial synthemes. 



Thus there would be an additional presumption in favour of 

 the supposed law of homonomial resolubility, provided that Mr. 

 Kirkman's solution were essentially distinct in type from my 

 own ; his binomial and trinomial systems, taken separately, coin- 

 cide in type with those afforded by my solution, notwithstanding 

 which it would not be lawful to assume (indeed I had at first some 

 reasons for doubting) the identity of type of the total groupings 

 of which these systems form part ; all we could have positively 

 inferred from that fact would have been, that these two groupings 

 both belong to the same class or genus containing 26,880 indi- 

 viduals, the second of the six referred to at the close of my last 

 paper; a comparison of the two solutions has, however, satisfied 

 me that they are absolutely identical in form. 



XXI. Proceedings of Learned Societies. 



KOYAL INSTITUTION OF GREAT BRITAIN. 



June 7, 1861. 



" f^^ tlie Pnvsical Basia of Solar Chemistry." By John Tyndall, 

 ^-S Esq., F.R.S., Professor of Natural Philosophy, Royal Insti- 

 tution. 



Omitting all preface, the speaker drew attention to an experi- 

 mental arrangement intended to prove that gaseous bodies radiate 

 heat in different degrees. Behind a double screen of polished tin 

 was placed an ordinary ring gas-burner; on this was placed a hot 

 copper ball, from which a column of heated air ascended : behind 

 the screen, but so placed that no ray from the ball could reach the 

 instrument, was an excellent thermo-electric pile, connected by wires 

 with a very delicate galvanometer. The thermo-electric pile was 

 known to be an instrument whereby heat was applied to the genera- 

 tion of electric currents ; the strength of the current being an accu- 

 rate measure of the quantity of the heat. As long as both faces of 

 the pile were at the same temperature no current was produced; 

 but the slightest difference in the temperature of the two faces at 

 once declared itself by the production of a current, which, when 

 carried through the galvanometer, indicated by the deflection of the 

 needle both its strength and its direction. 



The two faces of the pile were in the first instance brought to the 

 same temperature, the equilibrium being shown by the needle of the 

 galvanometer standing at zero. The rays emitted by the current of 

 hot air already referred to were permitted to fall upon one of the 

 faces of the pi'le ; and an extremely slight movement of the needle 

 showed that the radiation from the hot air, though sensible, was 

 extremely feeble. Connected with the ring-burner was a holder con- 

 taining oxygen gas ; and by turning a cock, a stream of this gas was 

 L2 



