On Drift. 11 



noble field in which they are labouring ; but we shall all do well, 

 gentlemen, in learning to doubt the completeness of our observa- 

 tions on difficult and controverted points when made under the 

 strong impressions of antecedent convictions. What I am espe- 

 cially anxious for is to see the American geologists resuming their 

 observations in all possible detail on this interesting subject, and 

 with candid reference to the different physical causes to which 

 smoothed and striated rocks have been attributed. There are few 

 phenomena more likely to elucidate the mixed and perplexing 

 operations of the period to which they must be referred. In 

 northern Europe M. Sefstrom has set us an admirable example, 

 by his careful and exact manner of making his observations, and 

 of mapping the results of them. There is still much room for 

 following out similar observations in the Scandinavian regions. 

 In our own islands, too, in Ireland, we have a field in which much 

 yet remains to be done. The observations on these points by my 

 friend Mr Griffith were made, as he has told me, a considerable 

 time ago, and incidentally rather than as forming a leading object 

 in his researches. It is not, therefore, to be expected that they 

 should be sufficient to satisfy the present requirements of the 

 science. If by these remarks, gentlemen, I should perchance lead 

 any geologist to reflect on the geological importance of this sub- 

 ject, and to make and record his observations upon it with more 

 than ordinary accuracy, I feel that I shall be attaining one of the 

 best objects for the accomplishment of which an address of this 

 kind may be rendered useful. 



I shall now proceed to make a few observations on the arrange- 

 ment of the materials which constitute the drift of Northern Europe. 

 Though in many cases this arrangement seems very confused, as 

 we might expect it to be, there does appear to be frequently a de- 

 cided predominance of finer material in the lower, and of coarser 

 material in the upper portion. The lower mass frequently con- 

 sists of fine argillaceous and arenaceous sediment, sometimes mixed 

 with rolled pebbles, and reposing immediately on the polished and 

 striated rocks. Taking the whole area of deposition in Norway, 

 Denmark, Sweden, Northern Russia, and Northern Germany, the 

 materials above described constitute the great mass of the drift ; 

 and on this mass generally the large erratic blocks are superin- 

 cumbent, though many blocks are also found imbedded within its 

 mass. The submarine origin of the general mass is rendered une- 

 quivocal by the organic remains which it is found in various loca- 

 lities to contain. 



The boundary of the area over which this enormous mass of 

 detrital matter has been deposited proceeds from a point east of 

 the White Sea towards the south-east, until it touches on one 

 point only on the Ural Mountains, whence it proceeds south of 

 Moscow to the Carpathian Mountains, and includes the whole of 



