158 A. p. COLEMAN 



thus far obtained. In reply it may be stated that the striated stones 

 are merely the climax of the evidence in favor of a Lower Huronian 

 ice age. The character and extent of the conglomerates themselves 

 are unaccountable on any other theory. If these conglomerates were 

 known only from a few small patches, one might perhaps invoke crush- 

 ing and faulting, or talus formation, or exceptionally heavy river cur- 

 rents to account for them; but when one finds that they often cover 

 many square miles, with thicknesses of hundreds or even more than 

 a thousand feet, and occur in every Huronian district with the same 

 characteristics, any such cause becomes incredible. It must be 

 remembered that, large as the conglomerate areas are, they represent 

 only remnants of a much more widely spread formation; for the 

 greater part they are merely bands caught in synclines during the 

 elevation of the Archaean mountain ranges. In the beginning the 

 conglomerate must have been far more extensive and was perhaps 

 continuous over the hundreds of thousands of square miles where it 

 is now found in scattered patches. The only comparable bowlder- 

 bearing formations known are the bowlder clays of Permo-Carbonif- 

 erous and Pleistocene times. Under these circumstances the burden 

 of proof lies with those who oppose the glacial origin of the Lower 

 Huronian conglomerate, and not with those who support it. 



Since there is only one older sedimentary formation, the Keewatin, 

 below the Lower Huronian, the glacial period j-ust described comes 

 very close to the beginning of known geological history. The surface 

 of North America was much colder then than at present, and there is 

 every reason to think that the earth's climates were then, as now, 

 controlled from without, and not influenced by stores of internal heat 

 much greater than in recent times. The earth has not cooled down 

 from the earliest ages known to geology, but may have kept a uniform 

 temperature, or may have been warming up as the ages advanced. 



If a Lower Huronian ice age is admitted, geologists should cease to 

 speak of the earth as once a molten globe, and to begin historical 

 geology with its cooling so as to form a soHd crust, on which, much 

 later, water could condense, and sedimentary deposits be formed. 

 There is no geological evidence of any such early history, and we 

 should not cling to an outworn nebular hypothesis which the astrono- 

 mers themselves are throwing overboard. 



