Septembeb 16, 1910] 



SCIENCE 



363 



of submergence. It is, however, generally 

 admitted that there have been oscillations 

 both of level and of climate since any 

 boulder clay was deposited in the district 

 south of the Humber and the Ribble. The 

 passing of the great ice age was not sud- 

 den, and glaciers may have lingered in our 

 mountain regions when paleolithic man 

 hunted the mammoth in the valley of the 

 Thames, or frequented the caves of Devon 

 and Mendip. But of these times of transi- 

 tion before written history became possible, 

 and of sundry interesting topics connected 

 with the ice age itself — of its cause, date 

 and duration, whether it was persistent or 

 interrupted by warmer episodes, and, if so, 

 by what number, of how often it had al- 

 ready recurred in the history of the earth 

 — I must, for obvious reasons, refrain from 

 speaking, and content myself with having 

 endeavored to place before you the facts 

 of which, in my opinion, we must take ac- 

 count in reconstructing the phj^sical geog- 

 raphy of western Europe, and especially of 

 our own country, during the age of ice. 



Not unnaturally you will expect a de- 

 cision in favor of one or the other litigant 

 after this long summing up. But I can 

 only say that, in regard to the British Isles, 

 the difficulties in either hypothesis appear 

 so great that, while I consider those in the 

 "land-ice" hypothesis to be the more seri- 

 ous, I can not as yet declare the other one 

 to be satisfactorily established, and think 

 we shall be wiser in working on in the hope 

 of clearing up some of the perplexities. I 

 may add that, for these purposes, regions 

 like the northern coasts of Russia and 

 Siberia appear to me more promising than 

 those in closer proximity to the north or 

 south magnetic poles. This may seem a 

 "lame and impotent conclusion" to so long 

 a disquisition, but there are stages in the 

 development of a scientific idea when the 

 best service we can do it is bj' attempting 



to separate facts from fancies, by demand- 

 ing that diiBculties should be frankly faced 

 instead of being severely ignored, by in- 

 sisting that the giving of a name can not 

 convert the imaginary into the real, and by 

 remembering that if hypotheses yet on 

 their trial are treated as axioms, the result 

 will often bring disaster, like building a 

 tower on a foundation of sand. To scru- 

 tinize, rather than to advocate any hypoth- 

 esis, has been my aim throughout this ad- 

 dress, and, if my efforts have been to some 

 extent successful, I trust to be forgiven, 

 though I may have trespassed on your 

 patience and disappointed a legitimate ex- 

 pectation. 



T. G. BONNEY 



THE FERTILITY OF TEE SOIL^ 



I BELIEVE it is customary for any one 

 who has the honor of presiding ever a sec- 

 tion of the British Association to provide 

 in his presidential addrer.s either a review 

 of the current progres'i of his sub,ject or 

 an accoiint of some large piece of investi- 

 gation by which he himself has illuminated 

 it. I wish I had anything of the latter 

 kind which I could consider worthy to 

 occupy your attention for the time at my 

 disposal ; and as to a review of the sub.iect, 

 I am not without hopes that the sectional 

 meetings themselves will provide all that 

 is necessary in the way of a general re- 

 view of what is going forward in our de- 

 partment of science. I have, therefore, 

 chosen instead to deal from an historic 

 point of view with the opinions which have 

 prevailed about one central fact, and I pro- 

 pose to set before you this morning an ac- 

 count of the ebb and flow of ideas as to the 

 causes of the fertilitj' of the soil, a question 

 which has naturally occupied the attention 



' Address by the chairman of the Agricultural 

 Sub-section of the British Association for the 

 Advancement of Science, Sheffield, 1910. 



