12 PEOCEEBINGS OP THE GEOLOGICAL SOCIETY. [JN^OV. 25, 



Mr. Mallet had remarked that nearly all river-courses are 

 in longitudinal section hollow curves which do, in their upper 

 reaches at least, appear to present more or less of the character of 

 parabolas. But although the well-known formula which expresses 

 the discharge at each point, and in fact the regimen of the stream, 

 might seem a pinori to countenance the idea that these curves are 

 parabolic, he is much disposed to think that the form of water- 

 channel does not depend upon any hydrodynamic law, but simply 

 upon the natural contour of the longitudinal sections of the river- 

 courses, which run almost always on the bare rocky skeleton of the 

 earth, and follow the forms, viewed on a broad scale, of all rocky 

 anticlinals, whose slopes are always more or less hollow curves. As 

 regards the long gently sloped lower reaches of all rivers, and more 

 particularly of great rivers, such as those appealed to by the author, 

 Mr. Mallet believed that it would be perfectly impossible to affirm 

 that their longitudinal sections conformed to any particular curve. 

 When plotted, such sections will be found to fit equally well to 

 right lines, or, if curved, to parabolas, ellipses, arcs of circles, or 

 what we please. 



Mr. Tyloe replied that he had not found definite evidence as to 

 the extension of corals downwards to such a depth as that men- 

 tioned by the President. With regard to oscillation, he had merely 

 treated of the southern part of England. The opening of the Straits 

 of Dover would account for the existence of beaches above the 

 present level, as the tides would have previously risen higher. The 

 parabolic curve was that which, by actual comparison, coincided 

 most closely with the longitudinal section of the banks of the rivers 

 Po, Mississippi, and Ganges. 



November 25th, 1868. 



The following communications were read : — 



1. On Floods in the Island o/Bequia. By G. M. Beown^e, Esq. 



(Communicated by the Secretary of State for Foreign Affairs.) 



[Abstract.] 



On the 17th of March, at 8 o'clock p.m., a steady strong wave was 

 seen bearing down upon Admiralty Bay ; it had no perceptible crest, 

 and was 3 feet in height ; it encroached upon the land to distances 

 varying from 70 to 350 feet. A second, smaller wave followed. No 

 shock of an earthquake was felt. 



Discussion. 



Dr. Duncan wished for some explanation of these earthquake - 

 waves, more especially with regard to the effects of supposed cata- 

 clysmic waves. He considered that they arose from sudden changes 

 in the level of shoals or littoral tracts, and not from deep-sea 

 disturbances. 



