198 R. D. Oldhsim—Some Bough Notes, 8fc. [No. 3, 



of the cmst relative to tlie central core of the earth ; but the more com- 

 pletely such an hypothesis may explain the absence of any trace of glacia- 

 tion in the Palaeozoic, Secondary, or Tertiray rocks of the Arctic regions, 

 to which Baron Nordenskjold has drawn our attention, the more irrecon- 

 cileable is it with the repeated traces of glacial action that are met 

 with almost within the tropics. Yet the latter as urgently requires 

 explanation as the former, and 1 have put these suggestions forward not 

 from any conviction of their intrinsic truth, but because I feel that the 

 rigid bonds within which mathematicians have sought to confine geo- 

 logists must be largely and materially relaxed, because I feel that every 

 addition to the growing pressure against these bonds is of some — even if 

 but small — ^importance, but chiefly because I trust that I may be instru- 

 mental in drawing the attention of others with greater opportunities 

 and greater abilities to the solution of this problem. 



P. S. — Just a week before this paper was read Mr. W. T. Blanford, 

 addressing the geological section of the British Association at Montreal, 

 devoted the greater part of his address to the consideration of a 

 subject to which he has before now referred, more particularly in the 

 Records of the Geological Survey of India, and on which I have cursorily 

 touched in the introductory part of this paper ; I mean the uncertainty 

 of paleeontological evidence in determining the exact correlation of 

 widely separated beds. He also refers to a report on the Stormberg 

 coal-fields by Mr. E. J. Dunne, which I have strangely overlooked : 

 Mr. Dunne mentions the existence of three species of plants in the 

 Stormberg beds identical with Australian species, an identification which, 

 if correct, greatly diminishes, if it does not altogether annihilate, the 

 value of my argument from the relationships between the African and 

 Indian early Secondary floras, but this is of the less importance, as, owing 

 to the known value or want of value of negative evidence in palaeonto- 

 logy, little value would in any case attach to an argument of this kind. 



