PRESIDENTIAL ADDRESS. / 



why they have obtained a foothold. I am confident that if the 

 geological scheme had yet to be devised upon the basis of the 

 advanced knowledge which naturalists have now acquired, it 

 would be free from the defects which I have mentioned. In 

 fact, it seems that these defects are due to the erroneous bio- 

 logical views which naturalists formerly entertained ; and that 

 they have remained solely because it is so difficult for men to 

 free their minds from impressions which have once become 

 firmly fixed, even after their fallacy has become apparent. 



These errors have by no means escaped the attention of lead- 

 ing naturalists ; and several years ago Prof. Huxley proposed the 

 term ik homotaxis " to express the existence of close biological 

 relationship between formations in different parts of the world 

 respectively, which might not, or could not, have been contem- 

 poraneously deposited. In using this term instead of "equiva- 

 lent," " synchronous," &c, as has usually been done in relation 

 to formations in separate regions which contain closely similar 

 faunas or floras, one does not thus commit himself to any opinion 

 as to the actual geological age of such formations, but only to the 

 fact that the forms of life were similar when and where those 

 formations were respectively deposited. Professor Huxley's idea 

 may be represented graphically by superimposing upon the dia- 

 gram which I have suggested a complementary series of lines. 

 much as isothermal lines are superimposed upon a map with its 

 lines of latitude. But to express the present state of our knowl- 

 edge, these complementary or isotaxial lines must be sadly 

 broken and fragmentary. 



This idea of homotaxy necessarily has reference to some 

 acknowledged standard of the order in which the geological 

 formations have been deposited ; and in using the term I shall of 

 course have reference to that which is in general use, which is 

 practically the European standard. 



Various authors have shown, not only that many formations 

 have been found in different parts of the world to be homotaxi- 



