394 Geological Society: — 



commenced to revolve in the opposite direction to that in which 

 the arms had been revolving. The movement kept up as long as 

 the candles were burning, and the speed was one revolution in two 

 minutes. 



The magnet was removed, the arms obeyed the force of radiation 

 from the candles and revolved rapidly, whilst the glass envelope 

 quickly came to rest and then rotated very slowly the same way as 

 the arms went. 



The candles were blown out; and as soon as the whole instru- 

 ment had come to rest a bar-magnet was moved alternately from 

 one side to the other of the radiometer, so as to cause the vanes 

 to rotate as if they had been under the influence of a candle. 

 The glass envelope moved with some rapidity (about one revolution 

 in three minutes) in the direction the arms were moving. On 

 reversing the direction of movement of the arms the glass envelope 

 changed direction also. 



These experiments show that the internal friction, either of the 

 steel point on the glass socket, of the vanes against the residual 

 air, or of both these causes combined, is considerable. Moving the 

 vanes round by the exterior magnet carries the whole envelope 

 round in opposition to the friction of the water against the glass. 



As there is much discussion at present respecting the cause of 

 these movements, and as some misunderstanding seems to pre- 

 vail as to my own views on the theory of the repulsion resulting 

 from radiation, I wish to take this opportunity of removing the 

 impression that I hold opinions which are in antagonism to some 

 strongly urged explanations of thes3 actions. I have on five or six 

 occasions specially stated that I wish to keep free from theories. 

 During my four years' work on this subject I have accumulated a 

 large fund of experimental observations ; and these often enable 

 me to see difficulties which could not be expected to occur to an 

 investigator who has had but a limited experience with the work- 

 ing of one or two instruments. 



GEOLOGICAL SOCIETY. 

 [Continued from p. 316.] 



June 21, 1876.— Prof. P. Martin Duncan, M.B., F.K.S., President, 

 in the Chair. 



The following communications were read : — 



3. " Pecent Glacial and Aqueous Action in Canada and the 

 Drift-Uplands of the^Province of Ontario." By the Pev. Wm. Bleas- 

 dell. Communicated by the President. 



The author stated that an enormous amount of glacial action 

 takes place every winter in Canada, especially on the river St. Law- 

 rence and its large lakes. "Anchor ice " and " pack ice " are drifted 

 down the stream, abrading and carrying off piece-meal the various 

 small islands studded along its course. A " shove," as it is termed, 

 often takes place on the breaking up of the ice ; the broken blocks 



