1867.] WHITAKER— TEETIAEY STRATA. 265 



EXPLANATIOiS^ OF PLATES XI. and XII. 



Plate XI. 



Specimen of Eozoon Canadense, imbedded in a dark-coloured homogeneous lime- 

 stone occurring in the Lower Laurentian series, at Tudor, Canada 

 West : two-thirds the natural size. 



Plate XII. 



Fig. 1. Section of one of the calcareous layers of the Tudor specimen (Plat« XL), 

 showing canal-system imperfectly infiltrated with black (carbona- 

 ceous ?) matter ; magnified 120 diameters. 



2. Section of the shelly layer of a specimen of Eozoon from Grenville, 



showing a minute form of canal-system partly injected with black 

 matter, and partly with serpentine; magnified 120 diameters. 



3. Siliceous bodies (internal casts?) from a specimen of Eozoon from 



Wentworth ; magnified 50 diameters. 



4. 5. Sections of a fragment of Eozoon from the Madoc limestone, showing 



various forms of canal-system filled with carbonate of lime ; mag- 

 fied 120 diameters. 



3. On SuBAERiAL Dentjbatiox, and on Cliffs and Escaepments of 

 the Tertiaet Strata. By W. Whitaker, Esq., B.A., F.G.S. 



[This paper was withdrawn by permission of the President.] 



(Abstract.) 



From the fact that escarpments differ from cliffs m. aU their chief 

 features, the author infers that the two could hardly result from 

 the same action, but that, whilst the latter were made by the sea, the 

 former seem to have been cut out by subaerial agents. 



The chief contrasts between the two kinds of ridges are : — 



(1) Escarpments always run along the strike. Cliffs rarely do 

 so. 



(2) The bottom of an escarpment is not at one level throughout. 

 That of a sea- cliff is. 



(3) At the foot of an escarpment one does not find a beach or 

 other trace of the action of the sea, but often such debris as would 

 be left by a slow and quiet denuding agent. 



(4) Two escarpments facing the same way often run near and 

 parallel to one another for many miles. Not so with cliffs. 



(5) The ridge of an escarpment is a nearly even line, and forms 

 the highest ground of the neighbourhood. The top of a cliff is 

 often very uneven and bordered by higher ground. 



From an examination of escarpments of the Chalk and of the 

 Tertiary beds, it was shown that though at first sight they might 

 seem like old lines of cliff, yet a little study would destroy the 

 fancied likeness, and it would be found that they are quite unhke 

 cliffs in the same beds; for though, from their winding outline, 

 these ranges of hills might remind one of some irregular coast, 

 caused by rocks of different hardness wearing away at different 



