Mr. G. P. Scrope on Lamination and Cleavage. 75 



been described in detail by Dr. Dawson; and pointed out his reasons 

 for regarding the Leda-clay of Dawson to be of contemporaneous 

 formation with the Nucula-clay of the eastern side of Lake Champlain, 

 and with the clay-beds of Albany and elsewhere on the Hudson. The 

 clay of the Hudson Valley lies on boulder-beds, and rarely contains 

 boulders. Along Lake Champlain similar clays overlie old drift, at 

 about 150 feet above the sea-level, and contain fossils similar to 

 those of the Montreal clays, at 140 feet above the sea, and of other 

 contemporaneous beds on the Ottawa. Prof. Ramsay assumed Dr. 

 Dawson's conclusion as to the age of the Leda-beds, which were 

 deposited, in a thickness of from 100 to 300 feet, over the boulder- 

 clay, whilst the sea covered the Ontario basin, and came up against 

 the great escarpment of Niagara limestone, which, now stretching 

 across this region, formed the southern coast of the glacial sea. 



The author then inferred that, the Erie plateau having been ele- 

 vated, the falls of Niagara commenced, by the drainage of the upper 

 lake-area, a little be/ore the close of the drift-period, falling first into 

 the sea over the edge of the escarpment above Queenstown and 

 Lewistown. If the 35,000 years suggested by Sir C. Lyell as the 

 minimum for the time occupied in the erosion of the gorge of Niagara 

 be approximately correct, though probably below the reality, we 

 have an idea of the amount of time that has elapsed since the close 

 of the drift-period. And, if it be ever found possible to accurately 

 determine the ancient rate of recession, we shall have data for a first 

 approach to an actual measurement of a portion of geological time. 

 This subject is intimately connected with the synchronism of the 

 mastodon-bearing freshwater strata of Niagara and those of the bluffs 

 of the Mississippi. 



2. " On Lamination and Cleavage occasioned by the mutual fric- 

 tion of the particles of rocks while in irregular motion." By 

 G. Poulett Scrope, Esq., M.P., F.R.S., F.G.S. 



The author referred to a former paper read by him before the 

 Society in April 1856, in which this subject was touched upon, and 

 proposed to carry on the inquiry as to the probable effect, upon the 

 internal structure of rocks, of the mutual friction of their com- 

 ponent parts, when forced into motion under extreme and irregular 

 pressures. He commenced by examining the laws that determine 

 the internal motions of substances possessing a more or less imjier- 

 fect liquidity, whether homogeneous, or consisting of solid particles 

 suspended in, or mixed with, or lubricated by, any liquid, under 

 unequal pressures ; and showed that unequal rates of motion must 

 result in the different parts of the substance, and that in the latter 

 case, there will be more or less separation of the solid and coarser 

 from the finer and liquid particles, into different zones or layers ; 

 those composed of the former moving less readily than those com- 

 posed of the latter ; and also that the former will, by the friction 

 attending this process, be turned round so as to bring their major 

 axes into the line of direction of the movements ; and, if susceptible 

 of tension or disintegration, will be elongated or drawn out in the 

 same direction. 



In illustration of this law, specimens uf marbled paper were pro- 



