Correspondence — Mr. A. J. Jukes-Browne — Mr. J. Carrie. 527 



publicly that the pores have the position there assigned to them, 

 and gives a properly enlarged drawing or photograph in support 

 of his statement, scepticism will be more than justified. 



F. A. Bather. 



coI^I^:Hls:F'OI^^^D:KlI^^GE. 



THE SUBMERGED PLATFORM OF WESTERN EUROPE. 



Sir, — The question of whether the border of this platform is an 

 escarpment or not cannot be left where Professor Hull leaves it, 

 for, as it stands, one of us must certainly have a false idea of the 

 meaning and use of the word escarpment. I am consequently 

 obliged to refer Professor Hull to textbooks for a definition, and 

 it will probably suffice if I quote the Student's Manual of Geology, 

 by Jukes & Geikie (3rd edition, p. 474) : "An escarpment is a cliff 

 or precipitous bank formed by the outcrop of a bed or series of beds 

 of harder consistency than those on which they rest." 



Professor Hull asserts that the question "is really one of form" 

 or shape of the ground, and he implies that the submerged declivity 

 is an escarpment because it "has a terraced upper surface, has a descent 

 sometimes almost precipitous, and falls off in a slope, sometimes 

 gentle, at its base into the abyssal plain." Then he proceeds to put 

 geological structure aside, which is precisely what the definition of 

 an escai'pment forbids him to do. It is quite true that the height 

 and length of a declivity are matters of degree, but if he cannot 

 show that a given declivity is formed by the outcrop of one series 

 of beds he has no right to call it an escarpment. 



Professor Hull, however, has another argument : he says, " the 

 question of the origin of the escarpment might have remained 

 problematical," but for the existence of the river channels which 

 cross the platform and open out through the " escarpment." He 

 regards these channels as being " unquestionable proof of subaerial 

 origin, both of themselves and of the physical features with which 

 they are connected." This is a novel argument certainly, but how 

 the existence of river-made valleys can possibly prove the declivity 

 to have been made by subaerial agencies passes my comprehension. 



Let us apply the argument to an existing terrestrial surface, and 

 for choice let us take Portugal ; then we have this syllogism ; — The 

 surface of Portugal is trenched by river- valleys which open through 

 the cliffs that form the western border of the land ; such valleys 

 prove all the physical features with which they are connected to 

 be of subaerial origin ; therefore the sea-cliffs of Portugal are 

 " escarpments " of subaerial origin ! 



No one wants to deny that the surface of the platform has once 

 been a land- surface, but I do deny that its border can properly be 

 called an escarpment or that there is any proof of its having been 

 fashioned by subaerial agencies. A. J. Jukes-Browne. 



ORTHITE. 

 Sir, — In the interesting and instructive paper on Scottish Rocks 

 containing Orthite, communicated by Dr. Flett to the September 

 number of the Geological Magazine, the author states that the 



