674 



BEPORT 1888. 



Subject of Diffusion 



' Qualifrj ' represented by ^^ NP 



Motion of a viscous fluid 



Closed electric currents within a 

 homoffeneous conductor 



Heat 



Substance in solution 



Electric potential in the conductor of a 

 submarine cable 



Ratio of the velocity at iV to the con- 

 stant velocity at O 



Current-density 



Ratio of temperature minus mean tem- 

 perature to mean temj)erature 



Ratio of density minus mean density to 

 mean density 



Ratio of potential at 2V to constant 

 potential at end O 



Examples. 



8. On Flux and Reflux of Water in Open Channels or in Pipes or other Ducts. 

 By Professor James Thomson, LL.B., F.B.S. 



In the autumn of 1872 I was staying at a place named Castlerock, on the north 

 coast of Ireland, between the mouth of the Bann river and the entrance to Lough 

 Foyle. There was an extensive sandy beach there, lashed by the great waves of the 

 Atlantic Ocean. At a part of that beach a small river or stream flowed to the 

 sea ; but the sandy beach had been thrown up as a bank, at about high-tide level, 

 obstructing what might have been the direct outfall course for the stream into the 

 sea, and causing the stream to turn to its right and to flow eastward for some 

 distance along the back of that sandy bank before finding an opening for flow out 

 to the sea. Thus, at the back of the bank, a little estuary was formed, along which, 

 when the tide was dowm, the stream would have for a considerable length a nearly 

 level bed, and into which, when the tide was up, the sea-water entered so as to fill 

 it up to various depths according to the height of the sea-surface. 



I happened to be watching with interest the motions of the water in this little 



