132 Prof. H. S. H. Shaw on the Boiling Contact of Bodies. [Apiil 29, 



that the same reasoning would not account for the turning of the 

 cylinder in the same direction as before with the above model, and 

 the lecturer then proceeded, by means of diagrams, to oifer an exj^lana- 

 tion of this and other phenomena. The various effects obtained with 

 bodies of different relative degrees of hardness were discussed at 

 length, but figures would be needed to make these points clear. 

 Finally, an explanation was given of the cause of an error which 

 always appeared in a certain imj)ortant class of integrators caused by 

 tlie slipj)ing of the edge of a disk over a surface on which it rolled iu 

 circumstances under which it had apparently never been suspected 

 that slipping did actually take place. This the lecturer had been 

 enabled to discover and measure by means of a special piece of appa- 

 ratus, a model of which was exhibited and the eflects shown by its 

 means. 



The facts and reasoning, which were given in the lecture, all 

 related to the rolling contact of bodies, and the lecturer ventured to 

 think that, imperfect as the treatment of the subject had been, it was 

 one of such importance, not merely from the point of view of the 

 practical applications he had mentioned, but in its scientific aspect, 

 dealing as it did from a novel point of view with the nature and pro- 

 perties of solid bodies, as to be worthy of being thus brought before 

 the Boyal Institution. 



