552 EEPOET — 1889. 



theories would make a very entertaining and instructive work. We should learn 

 from it, amongst other things, that the advance of our science has not always been 

 continuous — now and again, indeed, it has almost seemed as if the movement had 

 been retrograde. Knowledge has not come in like an overwhelming flood — like a 

 broad majestic river — but rather like a gently-flowing tide, now advancing, now 

 retiring, but ever, upon the whole, steadily gaining ground. The history I speak 

 of would also teach us that many of the general views and hypotheses which have 

 been from time to time abandoned as unworkable are hardly deserving of the 

 reproach and ridicule which we in these latter days may be inclined to cast upon 

 them. As the Scotch proverb says : ' It is easy to be wise behindhand.' It could 

 be readily shown that not a few discarded notions and opinions Lave frequently 

 worked for good, and have rather stimulated than checked inquiry. Such reflec- 

 tions should be encouraging to every investigator, whether he be a defender of the 

 old or an advocate of the new. Time tries all, and each worker may claim a share 

 in the final establishment of the truth. 



Perhaps there is no department of geological inquiry that has given rise to more 

 controversy than that which I have selected for the subject of this address. Hardly 

 a single step in advance has been taken without vehement opposition. But the 

 din of contending sides is not so loud now — the dust of the conflict has to some ex- 

 tent cleared away, and the positions which have been lost or maintained, as the 

 case may be, can be readily discerned. The glacialist who can look back over the 

 last twenty-five years of wordy conflict has every reason to be jubilant and hope- 

 ful. Many of those who formerly opposed him have come over to his side. It is 

 true he has not had everything; his own way. Some extreme views have been 

 abandoned in the struggle; that of a great polar ice-sheet, for example, as con- 

 ceived of by Agassiz. I am not aware, however, that many serious students of 

 glacial geology ever adopted that view. But it was quite an excusable hypothesis, 

 and has been abundantly suggestive. Had Agassiz lived to see the detailed work of 

 these later days, he would doubtless have modified his notion, and come to accept 

 the view of large continental glaciers which has taken its place. 



The results obtained by geologists, who have been studying the peripheral areas 

 of _ the drift-covered regions of our continent, are such as to satisfy us that the 

 drifts of those regions are not iceberg-droppings, as we used to suppose, but true 

 morainic matter and fluvio-glacial detritus. Geologists have not jumped to this 

 conclusion — they have only accepted it after laborious investigation of the evi- 

 dence. Since Dr. Otto Torell, in 1876, first stated his belief that the ' diluvium ' of 

 North Germany was of glacial origin a great literature on the subject has sprang 

 up, a perusal of which will show that with our German friends glacial geology has 

 passed through much the same succession of phases as with us. At first icebergs 

 are appealed to as explaining everything— next we meet with simdry ingenious 

 attempts at a compromise between floating-ice and a continuous ice-sheet. As 

 observations multiply, however, the element of floating-ice is gradually eliminated, 

 and all thepbenomena are explained by means of land-ice and ' schmelz-wasser ' 

 alone. It is a remarkable fact that the iceberg hypothesis has always been most 

 strenuously upheld by geologists whose labours" have been largely confined to 

 the peripheral areas of drift-covered countries. In the upland and mountainous 

 tracts, on the other hand, that hypothesis has never been able to survive a moderate 

 amount of accurate observation. Even in Switzerland — the land of glaciers — 

 geologists at one time were of opinion that the boulder-clays of the low groimds 

 had a different origin from those which occur in the mountain valleys. Thus it 

 was supposed that at the close of the Pleistocene period the Alps were surrounded 

 by great lakes or gulfs of some inland sea, into which the glaciers of the high val- 

 leys flowed and calved their icebergs — these latter scattering erratics and earthy 

 debris over the drowned areas. Sartorius von VValtershausen ' set forth this view 

 in an elaborate and well-illustrated paper. Unfortunately for his hypothesis, no 

 trace of the supposed great lakes or inland sea has ever been detected — on the con- 



' ' Untersuchungen iiber die Klimate der Gegenwart und der Vorwelt,' &c. 

 Natuurknndige Verhandelingfn v. d. Holland. Maatsoh. d. Wetensch. te Haarlem, 

 1865. 



