OBSERVATIONS AND CORRESPONDENCE. 



The Permanence of Ocean Basins. 



It seems desirable that I should say a few words in reply to Dr. Blanford's 

 letter in the last issue (p. 639), and to Mr. Jukes-Browne's article in the preceding 

 number of Natural Science (pp. 508-513). 



Both these writers lay stress upon a supposed considerable modification of my views 

 in my late paper. I reply that there is no real alteration ; because the i ,000-fathom 

 line was never adduced by me as an absolute and rigid boundary between the oceanic 

 and continental areas, but as a general indication of their respective limits according 

 to the best obtainable evidence. In proof of this, I may point out that even in the 

 first edition of "Island Life" (p. 444) I refer to a submarine plateau at a depth of 

 between 1,000 and 2,000 fathoms, which stretches southward from New Zealand 

 towards the Antarctic continent, and suggest an ancient connection " with the Great 

 Southern Continent by means of intervening lands and islands"; and in my 

 " Darwinism " (p. 346) I define the permanence of oceanic and continental areas as 

 meaning that, " while all of them have been undergoingchangesof outline and extent 

 from age to age, they have yet maintained substantially the same positions, and 

 have never actually changed places with each other " ; and again, at p. 347, after 

 stating that the 1,000-fathom line " marks out, approximately, the continental area," 

 I add : " There may, of course, have been some extensions of land beyond this limit, 

 while some areas within it may always have been ocean ; but so far as we have any 

 direct evidence, this line may be taken to mark out, approximately, the most pro- 

 bable boundary between the continental areas and the great oceanic basins." 



In my recent paper I have merely repeated and enforced these statements by 

 showing how little real difference is made by carrying the possibilities of Continental 

 extension, in rare cases, as far as the 1,500- or 2,000-fathom line. There is, there- 

 fore, no ground for alleging any departure from supposed " extreme views " which I 

 formerly held, since the fresh arguments I have adduced show any great extension 

 beyond the 1,000-fathom line to be in the highest degree improbable. 



Dr. Blanford objects to my statement that the theory of the permanence of the 

 ocean basins was " attacked " by him. Perhaps the word was not well chosen, and 

 I should have said " criticised," but it was held by Mr. Jukes-Browne to be such a 

 damaging criticism- that (in private correspondence) he expressed^ surprise that I 

 had not replied to its arguments in the new edition of " Island Life." But though 

 the passage quoted by Dr. Blanford is not very antagonistic, there is much in the 

 "Address" itself that is altogether opposed to my \iews. Forinstance, the writer argues 

 in favour of a former land-connection between South America and Africa, which he 

 says is " chiefly shown by tropical forms," though adding, "but these may have 

 migrated far southward during warm periods; ' and, later on, he speaks of a possible 

 " girdle of land, chiefly in low latitudes, round nearly three-quarters of the globe, 

 from Peru to New Zealand, and the Fiji Islands." But any such land-extension as 

 this is so wholly inconsistent with the permanence of the great ocean basin of the 

 Pacific, that to argue in favour of it is certainly to attack the theory of permanence. 

 Again, a direct land-connection between South Africa, Madagascar, and the Penin- 

 sula of India is very strongly advocated, but the 1,000-fathom line shows us an actual 

 though slightly circuitous connecuon by means of existing continental areas between 

 Africa and India, and to hold that this would have been insufficient — why, I cannot 



