fi On Drift. 



obstacles. Such effects might also be produced by the passage of 

 masses of detritus. The former is a probable, the latter a possible 

 mode of producing these phenomena. When the opponent of the 

 glacialist, therefore, urges the latter against the former mode of 

 action (except under some particular condition), let him also 

 institute a self-examination as to whether he is exercising his 

 unclouded and unprejudiced judgment. Gentlemen, I would 

 exhort you earnestly to prosecute your researches and speculations 

 with a fair and liberal feeling towards the views of others, and 

 especially with an unflinching obedience to the laws of inductive 

 philosophy. Every geologist, who takes an impartial review of 

 the history of his own mind with reference to geological opinions, 

 will probably feel that what is termed consistency of opinion would 

 frequently have been in his own case persistency in error. I feel 

 the more entitled to make these remarks, from the consciousness 

 of having resigned much of my own early convictions respecting 

 the glacial theory ; and I make them in immediate connection 

 with the subject before us, because I believe that much remains 

 to be done in these superficial deposits before we can completely 

 interpret them; and I believe also, that for our progress towards 

 sound opinion and unity of view respecting them, ability and 

 fidelity in the observer will scarcely be more necessary than that 

 fairness and candour without which he will assuredly fail to bring 

 his observations as true tests of the different views with which 

 the subject is at present perplexed. Let us not seek for mere 

 possibilities in support of antecedent opinions, but submit our 

 views constantly to the test of enlarged experience and careful 

 induction. There may be, doubtless, a stage in the progress of 

 science in which new views, thrown out at random, and the advo- 

 cacy of individual opinion with somewhat more than philosophical 

 pertinacity, may be effective in the development of truth; but 

 there is assuredly also another and more advanced stage of science, 

 in which such habits of mind can only retard and embarrass its 

 progress, and impede our arrival at those ultimate truths which 

 it may be our object to establish. At this latter stage I believe 

 the science of geology to have arrived ; and if by these remarks I 

 should induce one speculative geologist to watch with increased 

 rigour the reasoning by which he arrives at his convictions, I shall 

 perhaps have done more for our science than I can do by any 

 detailed information which an occasion of this nature may enable 

 me to bring before you. 



I shall now direct your attention to some of the leading cha- 

 racters, of the great mass of drift which extends over so large a 

 portion of northern Europe. And first I shall speak of the stritv 

 which so abound in the northern part of the region in question. 

 When regarded with reference to a limited area, their directions 

 might be described as characterised by the law of parallelism ; but 



