1812. Mr. 34.] PEOFESSOR DAVY. 371 



experiments as a sequel, illustrated with drawings ; 

 the whole made a small quarto of 386 pages, with an 

 index of twenty-five pages. The volume was bound 

 by Mr. Faraday, and was sent to Davy as an evidence of 

 Faraday's ' knowledge, diligence, and order,' when he 

 asked for an engagement at the Eoyal Institution. 



Davy gave the lecture on Radiant Matter on Feb- 

 ruary 29. He said, ' With respect to radiant or ethe- 

 real substances all our knowledge of it is obtained 

 from the effect it produces on us and terrestrial bodies 

 when in motion. 



'In our consideration of this subject it will be 

 essentially necessary that we distinguish between know- 

 ledge and speculation. These terms in their meaning 

 are palpably different, but yet have been intermixed 

 and combined together in a very singular manner. 

 The French chemists in particular speak of the 

 materiality of heat, and of the nature of the compounds 

 it forms, as confidently and as fluently as if they had 

 undeniably proved it to be a body. They have blended 

 their knowledge with speculation, and formed a theory 

 that is very possibly untrue. The most eminent 

 phenomena of radiation are to be observed in light.' 



And then he passed on to the laws of light and 

 dwelt on Herschel's discovery that the heating power 

 of red rays was to the green as fifty-five to sixteen, 

 and that he had himself found the thermometer 

 rose still higher beyond the red, and that heating rays 

 are less refrangible than light rays ; then he showed 

 a wire heated by the voltaic battery in air and in 

 vacuo, and said that he had proved ' that the radiat- 



B B 2 



