1 88 LIGHT SCIENCE FOR LEISURE HOURS. 



ments, when their effects are considered for a sufficient 

 lapse of ages, is eminently beneficial, and that they 

 constitute an essential part of that mechanism by which 

 the integrity of the habitable surface is preserved. Why 

 the working of this same machinery should be attended 

 with so much evil, is a mystery far beyond the reach of 

 our philosophy, and must probably remain so until we 

 are permitted to investigate, not our planet alone and 

 its inhabitants, but other parts of the moral and material 

 universe with which they may be connected. Could 

 our survey embrace other worlds, and the events, not 

 of a few centuries only, but of periods as indefinite as 

 those with which geology renders us familiar, some 

 apparent contradictions might be reconciled, and some 

 difficulties would doubtless be cleared up. But even 

 then, as our capacities are finite, while the scheme of 

 the universe must be infinite, both in time and space, it 

 is presumptuous to suppose that all sources of doubt and 

 perplexity would ever be removed. On the contrary, 

 they might, perhaps, go on augmenting in number 

 although our confidence in the wisdom of the plan of 

 nature might increase at the same time ; for it has been 

 justly said ' (by Sir Humphry Davy) ' that the greater 

 the circle of light, the greater the boundary of darkness 

 by which it is surrounded.' 



(From the Cornhill Magazine, March 1868.) 



