546 LIGHT SCIENCE FOR LEISURE HOURS. 



observation than by reasoning on imperfect knowledge. 

 If I venture to remark that his deep-sea researches 

 have led to the most important contribution which has 

 been added for many years to our information respect- 

 ing oceanic circulation, he will not, I trust, consider 

 that I am passing beyond the bounds of controversial 

 courtesy. But I am, indeed, not anxious to treat the 

 matter as one for controversy in any sense. It will be 

 perceived by those who have read my remarks on the 

 subject, that I have rather put them forward as sug- 

 gestions than as indicating theories which can be 

 maintained with any degree of assurance, far less with 

 conviction. Nor does it seem to me likely that one 

 explanation can suffice to account for all the pheno- 

 mena recognised in oceanic circulation. This is a case, 

 if ever such case were, in which more causes are in 

 operation than one ; so that it may very well happen 

 that excellent arguments can be adduced in main- 

 tenance of different views. If, therefore, I enter on 

 the defence of what I have already written on this 

 subject, it is not with the wish to show that one parti- 

 cular explanation of oceanic circulation is correct, and 

 all others erroneous. If I am desirous of dealing with 

 the considerations urged by Dr. Carpenter, it is not 

 because they seem to him to militate against the views 

 I have to some extent advocated. What I wish to 

 show is that I have not addressed your readers on 

 the subject of oceanic circulation without making 

 myself familiar with the facts which bear upon that 

 subject, and at the very least, with those compara- 



