Ixiv PROCEEDINGS OF THE GEOLOGICAL SOCIETr. [May I90I, 



and it is therefore possible to get into such a condition as not to be 

 able to see the wood for the trees, to lose the due sense of propor- 

 tion, and to become mere machines for tabulating interminable 

 trivialities. 



On the other hand, it should be remembered that every worker 

 endowed with imagination must formulate, in his own mind, many 

 theories that will not stand the test of verification, and that it is 

 quite unnecessary for him to trouble other workers with such 

 theories. He can test them for himself, and relegate them to 

 oblivion if necessary, without burdening our overcrowded book- 

 shelves with crude speculations and unverified hypotheses. 



It is only when a theory has proved its usefulness as a coordinator 

 of fact that it becomes worthy of the dignity of publication. It 

 may be true, or false, most likely the latter ; but if it coordinates 

 more facts than any other, it is at any rate useful, and may be 

 conveniently retained until replaced by a better. Controversy as to 

 the truth or falsity of a theory often seems to me beside the mark, 

 for if a given theory coordinates more facts than any other, it is at 

 least worthy of respect, and may be tentatively held as a working 

 hypothesis, along with the conviction that it is not true, or only 

 partiall}^ true. Indeed, the controversial spirit is, in my judgment, 

 inimical to the best interests of science. It makes a man more 

 eager to refute than to understand the views of his opponents ; it 

 tends to check the flow of sympathy, and thus often prevents that 

 friendly cooperation which is so desirable in the interest of scien- 

 tific progress. When controversy becomes acute, I always feel 

 inclined to exclaim ' a plague on both your houses ! ' 



Every branch of our many-sided science has benefited by the zeal 

 for collecting facts which manifested itself during the early years 

 of the nineteenth century. Methods of observation have been 

 perfected, national surveys and private individuals have examined, 

 and are examining, the geological structure of every civilized State, 

 and explorers have penetrated to almost every quarter of the globe. 

 Our libraries and museums are being rapidly filled with records of 

 all this scientific activity. Side by side with the registration and 

 cataloguing of facts there has taken place an evolution of scientific 

 ideas, and it is on this aspect of the subject, so far as my own 

 special branch is concerned, that I propose to offer a few remarks. 



Eocks may be studied from two more or less distinct points of 

 view, the descriptive and the aetiological. But it is well to note 



