92 , Reports and Proceedings — 



occurring at heights much above the Welsh Lakes, which were, 

 however, not occuj)ied by marine beds. 



The writer expressed his regret that when Mr. Trimmer found, in 

 1831, the markings or scratches, which he rightly pronounced glacial, 

 made distinctly on the face of the Tryfaen Eocks, and covered by 

 the fossiliferous marine drift, he did not infer that a Glacial Period 

 had once existed in Wales. The great discovery was made by 

 Agassiz in 1837 that there was an Ice Period at one time almost all 

 over the world. 



Some of the best examples of the rapid formation of a recentfluviatile 

 stratum were in India. A deposit was there described made by but 

 a small mountain stream measuring a million cubic feet in a month. 



Eivers flowing in uniform motion for hundreds of miles, often 

 depositing but a small portion of sand and mud, carry out a great 

 mass of solid matter in suspension, and along their river channels, 

 and push the material into the sea, furnishing material for marine 

 littoral deposits. 



The case of the Danube bar, where a rapid denudation 650 feet 

 wide has been produced by artificial piers arranged by Sir 0. Hartley 

 so as to concentrate the river-current and make an opposite current 

 from the sea, was referred to. 



Sir H. T. De la Beche observed that the dry land valleys along 

 the English coast were not prolonged into the Channel. The source 

 of the material to. fill them must have been the sands brought in 

 from deeper water or from the rivers. 



The writer pointed to the immense cuts out of solid strata or 

 rocks in the estuaries of the Thames, Seine, and Severn, to show 

 how the alternate and often opposite action of the river and tide 

 favoured denudation. The sea alone could not penetrate an iron- 

 bound coast in this manner. 



The sea throws up beaches all along the coast, as well as littoral 

 deposits. Chesil Beach is a conspicuous example, with its lagoons 

 behind, and its form approaching a binomial curve, to which all 

 beaches approximate. The Eio Grande Beach, 100 miles long, 

 10 miles wide, inclosing a fresh-water lagoon 20 miles wide, 100 

 miles long, was referred to as a recent deposit, like that, on a small 

 scale, at Shoreham, near Brighton. 



A drawing to scale showed that the course of the Chesil Beach could 

 be closely represented by a binomial curve. 



The writer had previously applied this curve to indicate the true 

 form of hills, when not disturbed by beds of unequal hardness or 

 permeability. The lower part of this curve is a parabola, and the 

 longitudinal sections of large navigable rivers (of which the Ganges 

 is a good instance) follow this curve. The law of uniform motion 

 of rivers and the effect of weight and slope on velocity were illus- 

 trated by diagrams. 



Marine deposits and marine denudation may be well observed in 

 many real instances on our coast. The writer was unable to find a 

 good example of a plane of marine denudation, a term in general 

 use among geologists ; but he had found in the Estuary of the La 



