60 THE POPULAR SCIENCE MONTHLY. 



himself it is "demonstrably contrary to fact" to allege that 

 geology " knows nothing " of them. The science knows of them 

 so well and so familiarly that " the last great depression " has he- 

 come a stock phrase among Quaternary geologists as referring 

 to many ascertained phenomena which are capable of no other 

 interpretation. 



It may, however, be well asked how it is, if these three great 

 facts have been established, that the conclusions flowing from 

 them have not been followed up. The explanation is as easy as 

 it is instructive. It has been due to that one cause which, perhaps 

 more than any other, has impeded the advance of science the 

 blinding effect of invincible preconceptions. Sometimes these 

 have been aggravated by such intellectual aversions as that 

 which animates Prof. Huxley against everything connected with 

 Christian theology. But many desperate preconceptions have 

 other sources. The authority of great men who have fallen into 

 some great error has been one of the barriers most difficult to 

 breach. Of this kind perhaps the most memorable example was 

 the power of Sir Isaac Newton to postpone for nearly a century 

 and a half the establishment of the undulatory theory of light. 

 The furious and contemptuous attacks made upon Dr. Thomas 

 Young, when in our own day he revived that theory and poured 

 the light of his own genius upon it, remind one very much of the 

 temper and the spirit in which some men are now meeting those 

 movements of discovery that tend to reopen questions which only 

 ignorance had closed, and to give to old ideas a new and scientific 

 basis. Then there has been another source of abounding preju- 

 dice. The shape in which those old ideas were at first presented 

 has often been really deforming and erroneous. This has been 

 pre-eminently the case with the form under which the idea of a 

 deluge has come across the pathway of geology. At first men 

 would not believe in the reality of fossil shells. When' this reality 

 was proved to demonstration, then the supposition was entertained 

 that they were carried into the solid rocks by the Noachian Del- 

 uge. The absurdity of this supposition was almost sickening, 

 and it established a lasting sense of nausea in all the stomachs of 

 geologists at the very mention of a deluge as coming at all within 

 the cognizance of their science. This is just the attitude of mind 

 which sets up the most insuperable preconceptions, and renders 

 men insensible to the force of any evidence which even seems to 

 look in the direction of their disgust. In this very article Prof. 

 Huxley makes a confession upon this subject, which he does not 

 mean as such, but which, nevertheless, is a confession most true 

 and most significant. "At the present time," he says, " it is diffi- 

 cult to persuade serious scientific inquirers to occupy themselves 

 in any way with the Noachian Deluge. They look at you with a 



