THE SIX GATEWAYS OF KNOWLEDGE. 295 



contact with the heated air which has ascended 

 from the poker, and by radiant heat felt by 

 your sense of heat, and by radiant heat seen as 

 light (the iron being still red-hot). But the sense 

 of heat is the same throughout, and is a certain 

 effect experienced by the tissue, whether it be 

 caused by radiant heat, or by contact with heated 

 particles of the air. 



Lastly, there remains and I am afraid I have 

 already taxed your patience too long the sense 

 of force. I have been vehemently attacked for 

 asserting this sixth sense. I need not go into 

 the controversy, nor try to explain to you the 

 ground on which I have been attacked ; I could 

 not in fact, because in reading the attack I have 

 not been able to understand it myself. The only 

 tangible ground of objection, perhaps, was that 

 a writer in New York published this theory in 

 1880. I had quoted Dr. Thomas Reid, without 

 giving a date; his date chances to be 1780 or 

 thereabouts ! ! But physiologists have very strenu- 

 ously resisted admitting that the sense of 

 roughness is the same as that muscular sense, 



