16 JDr. J. W. Spencer — The Submerged Platform of W. Europe. 



they exhibit various points of resemblance that may easily be 

 mistaken for indications of real affinity. 



In the Amphibians, especially in the oldest forms, there are hints 

 of a true relationship with both Eeptiles and Mammals. It seems 

 to me, therefore, that in some of the minute primitive forms, as old 

 as the Devonian, if not still moi-e ancient, we may yet find the key 

 to the great mystery of the Origin of Mammals. 



IV. — Prof. Hull's " Submerged Platform of Western Europe." 

 £y Prof. J. W. Spencer, M.A., Ph.D., B.A.Sc, F.G.S. 



ME. JUKES - BROWNE'S contribution to this subject, in the 

 September number of the Geological Magazine, brought out 

 a clear reply from Professor Hull in the next issue. Here the 

 argument practically ceased, for in his letter in November 

 Mr. Jukes-Browne turned his correspondence into an academic 

 disputation of the meaning of the word ' escarpment,' for which 

 other expressions could have been used, and the flat denial of the 

 evidence submitted by Professor Hull. This is to be greatly 

 regretted, for Mr. Jukes-Browne does not show evidence to the 

 contrary, nor that he has investigated any of the facts for himself — 

 such as the contouring of the fullest charts with isobars of two 

 hundred or three hundred feet apart — before pronouncing his ipse 

 dixit. 



Mr. Jukes-Browne challenges the analogy drawn by Professor 

 Hull between the drowned declivities, facing the continental shelf, 

 and the slopes — whether steep, abrupt, or precipitous — which mark 

 the descent from an elevated tableland, plateau, or even lower plain 

 to the country below. Although Professor Hull uses the word 

 ' escarpment ' as covering this topographical feature, in exactly 

 the sense commonly understood in America, I purposely avoid its 

 adoption, so as not to allow of the diversion from the phenomena 

 themselves. Mr. Jukes-Browne asks if Professor Hull can point 

 out such a conspicuous declivity from one jolatform to lower plains 

 " anywhere in Europe which has a length of 700 miles and a height 

 above its base of 7,000 to 8,000 feet." The question appears to 

 imply a negative answer, to be used as a refutation of Professor 

 Hull's inferences. The question should not have been limited to 

 evidence obtainable in Europe, where presumably such a feature 

 is not likely to be found, but should have been extended to any 

 region. With this latitude for reply, the reader may have the 

 opportunity of knowing (as I certainly think Mr. Jukes-Browne 

 has had) that the great face of the Mexican tableland is characterized 

 by an abrupt slope reaching down 6,500 feet to the inner edge of 

 the coastal plain, or over 8,000 feet to the Gulf of Mexico. This 

 slope has a length of several times 700 miles, and extends from 

 Mexico into the United States. In point of magnitude and abrupt- 

 ness, and also of the character of the dissecting valleys, this Mexican 

 slope can quite as well be taken for comparison with Professor 

 Hull's declivities as if found in Europe. 



