1 86 HUTTONIAN THEORY 



of the rocks should be rigorously revised, with the 

 view of ascertaining how far that interpretation may 

 be capable of modification or amendment. But we 

 must also remember that the geological record con- 

 stitutes a voluminous body of evidence regarding the 

 earth's history which cannot be ignored, and must be 

 explained in accordance with ascertained natural laws. 

 If the conclusions derived from the most careful study 

 of this record cannot be reconciled with those drawn 

 from physical considerations, it is surely not too much 

 to ask that the latter should be also revised. It was 

 well said by Huxley that the mathematical mill is an 

 admirable piece of machinery, but that the value of 

 what it yields depends upon the quality of what is 

 put into it. That there must be some flaw in the 

 physical argument I can, for my own part, hardly 

 doubt, though I do not pretend to be able to say 

 where it is to be found. Some assumption, it seems 

 to me, has been made, or some consideration has 

 been left out of sight, which will eventually be seen 

 to vitiate the conclusions, and which when duly taken 

 into account will allow time enough for any reason- 

 able interpretation of the geological record. 



In problems of this nature, where geological data 

 capable of numerical statement are so needful, it is 

 hardly possible to obtain trustworthy computations of 

 time. We can only measure the rate of changes in 

 progress now, and infer from these changes the length 

 of time required for the completion of results achieved 

 by the same processes in the past. There is fortu- 

 nately one great cycle of movement which admits of 

 careful investigation, and which has been made to 



