224 GEOLOGICAL TIME 



gation is almost boundless, for there is hardly a depart- 

 ment of geological dynamics over which it does not 

 extend. The range of experimental geology must be 

 widely enlarged, until every process susceptible of 

 illustration or measurement by artificial means has 

 been investigated. Field-observation needs to be sup- 

 plemented where possible by instrumental determin- 

 ation, so as to be made more precise and accurate, 

 and more capable of furnishing reliable numerical 

 statistics for practical as well as theoretical deductions. 

 The subject is too vast for adequate treatment here. 

 But let me illustrate my meaning by selecting a few 

 instances where the adoption of these more rigid 

 methods of inquiry might powerfully assist us in 

 dealing with the rates of geological processes and the 

 value of geological time. Take, for example, the 

 wide range of lines of investigation embraced under 

 the head of Denudation. So voluminous a series of 

 observations has been made in this subject, and so 

 ample is the literature devoted to it, that no depart- 

 ment of geology, it might be thought, has been more 

 abundantly and successfully explored. Yet if we look 

 through the pile of memoirs, articles and books, we 

 cannot but be struck with the predominant vagueness 

 of their statements, and with the general absence of 

 such numerical data determined by accurate, systematic, 

 and prolonged measurement as would alone furnish a 

 satisfactory basis for computations of the rate at which 

 denudation takes place. Some instrumental observa- 

 tions of the greatest value have indeed been made, 

 but, for the most part, observations of this kind have 

 been too meagre and desultory. 



