14 WORLD-MAKING 



of the reaction of mind on nature, and must be largely sub- 

 jective and anthropomorphic. Hence, no doubt, arises much 

 of the controversy of science, and much of the unsolved diffi- 

 culty. We recognise this when we divide science into that 

 which is experimental, or depends on apparatus, and that which 

 is observational and classificatory — distinctions these which 

 relate not so much to the objects of science as to our methods 

 of pursuing them. This view also opens up to us the thought 

 that the domain of science is practically boundless, for who 

 can set limits to the action of mind on the universe, or of the 

 universe on mind. It follows that science, as it exists at any 

 one time, must be limited on all sides by unsolved mysteries ; 

 and it will not serve any good purpose to meet these with 

 clever guesses. If we so treat the enigmas of the sphinx 

 nature, we shall surely be devoured. Nor, on the other hand, 

 must we collapse into absolute despair, and resign ourselves to 

 the confession of inevitable ignorance. It becomes us rather 

 boldly to confront the unsolved questions of nature, and to 

 wrestle with their difficulties till we master such as we can, 

 and cheerfully leave those we cannot overcome to be grappled 

 with by our successors. 



Fortunately, as a geologist, I do not need to invite attention 

 to those transcendental questions which relate to the ultimate 

 constitution of matter, the nature of the ethereal medium filling 

 space, the absolute difference or identity of chemical elements, 

 the cause of gravitation, the conservation and dissipation of 

 energy, the nature of life, or the primary origin of bioplasmic 

 matter. I may take the much more humble role of an in- 

 quirer into the unsolved or partially solved problems which 

 meet us in considering that short and imperfect record which 

 geology studies in the rocky layers of the earth's crust, and 

 which leads no farther back than to the time when a solid 

 rind had already formed on the earth, and was already covered 

 with an ocean. This record of geology covers but a small 



