390 EHRENFELD— JOINTING AS A FUNDAMENTAL FACTOR 



atmospheric erosion and marine erosion as two stages of a con- 

 secutive process. 



There remains further the consideration of this in connection 

 with the outhned shapes of the various continental shelves; the 

 rapid descent of the lithosphere off these shelves being a general 

 characteristic of all. The consideration of this subject must be 

 with our limited information so largely speculative that it is not a 

 subject which I now wish to discuss. The idea of attempting to 

 carry the repeating patterns out to the sea floor beyond the limits 

 of the shelves and to try to establish joint influence in the distri- 

 bution of oceanic islands may however prove to be connected with 

 the rise of blocked masses of the lithosphere. 



It was proposed earlier in this paper to apply the method of 

 " repeating patterns " to some island groups not connected closely 

 to continental shelf land in order to draw a comparison if possible 

 of similar jointing control in their distribution. 



For the purpose of such comparison the following groups have 

 been chosen though it is not by any means believed that these are 

 the only ones which would yield concordant results ; these are first 

 the group of the Isles of The Shoals in the Gulf of IMaine, secondly 

 the Canary and ^^^ladeira group. With these for the sake of further 

 development of the argument will be compared the islands of 

 Oceania of the Pacific. It is not my intention to discuss in any 

 detail the general geology of any of these groups, what it is de- 

 sired to bring forth is their group morphology or more particularly 

 the relations of their positions to each other. To consider the 

 Shoals group first, this is a group of about seven actual islands 

 with however a number of rock ledges which though submerged 

 beneath the tide are an essential part of the construction of the 

 whole group as may be seen from the navigation charts.'^ The 

 figures or plotting of position are taken from chart io8. 



The nearness to the present shore line of these islands with 

 their rather evident similarity of position to other groups of islands 

 in the same general vicinity makes no argument as to their essen- 

 tial connection with the mainland necessary. This is especially 



38 See Chart No. io8, Wells to Cape Ann, U. S. Coast and Geodetic Sur- 

 vey. Also U. S. Coast Pilot, Atlantic Coast, Pts. I. and II., pp. 142-143- 



