338 



bending a prism of ice by fracture and regelation, does not prove 

 that ice is non-viscous. This is perfectly true ; nor is it conceived 

 that the onus rests on us to prove the negative here. All that is 

 claimed for the foregoing experiments is the referring of certain ob- 

 served phenomena to a true cause, instead of to an imaginary one. 

 An illustration may perhaps serve to place this question in its true 

 light. By Newton's calculation, the velocity of sound through air 

 was one-sixth less than what observation made it ; and to account 

 for this discrepancy he supposed that the sound passed instan- 

 taneously through the particles of air, time being required only to 

 accomplish the passage from particle to particle. He supposed the 

 diameter of each air-particle to be A-f| ths of the distance between 

 two particles, and nobody ever proved him wrong. Still, when 

 Laplace assigned a vera causa for the discrepancy, the hypothesis of 

 Newton, and other ingenious suppositions, were discarded. The 

 proof indeed in such cases consists in the substitution of a fact for 

 a conjecture ; and whether this has been done in the case now before 

 us, the intelligent reader must himself decide. 



January 22, 1857. 



Dr. W. A. MILLER, V.P., in the Chair. 

 The following communications were read : 



I. " On some of the Products of the Destructive Distillation of 

 Boghead Coal." Part I. By C. GREVILLE WILLIAMS, Esq., 

 Assistant to Dr. ANDERSON, Professor of Chemistry in the 

 University of Glasgow. Communicated by Dr. SHARPEY, 

 Sec. R.S. Received November 25, 1856. 



(Abstract.) 



The paper, of which the following is a brief abstract, constitutes 

 the first part of the author's examination of the hydrocarbons con- 



