652 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



tion increased the land area to 55,000,000 square miles, which is roughly the 

 present area of the lands.* 



The annual rate of the supply of calcium to the ocean was, on these 

 assumptions, increased from (55/20x2=) 5-5 to (55/20x5+=) 14 + times by the 

 late-Huronian crustal movements. But the sea-bottom area over which the 

 chemical precipitation of calcium carbonate was compelled was halved by those 

 movements. Thus the post-Huronian conditions favouring the possibility that 

 a part of the river-borne calcium could remain in solution in the ocean were 

 from (5-5x2=) 11 to (14x2=) 2S or more times more effective than the pre- 

 Huronian conditions. 



Although little stress can be laid on any particular figure embodied in the 

 foregoing conclusions, this rough analysis serves to illustrate the strength of the 

 probability that the prodigious crustal movements of the late-Huronian and 

 pre-Cambrian interval made a comparatively rapid and quite drastic change in 

 the chemical condition of the ocean. 



Analyses of the Ottawa River. 



The view that the supply of calcium to the ocean reached a maximum rate 

 toward the close of pre-Cambrian time is based on some speculation. Appar- 

 ently more certain are the grounds for believing that the late pre-Cambrian ocean 

 could have received an annual calcium supply which was only a small fraction 

 of the present annual supply. The belief may be founded on a comparison 

 between the analyses of rivers now draining large pre-Cambrian areas with the 

 analyses of rivers draining average terranes of the present continents. 



Few rivers are more typical of the former class than the Ottawa above 

 Ottawa city. Its thousands of miles of trunk and branch channels are sunk 

 in the largest pre-Cambrian area of the world, and it happens that most or all 

 of the recognized rock types of the pre-Cambrian formations are liberally repre- 

 sented in its drainage basin. Only very small and practically negligible masses 

 of younger rocks occur in the basin above the city of Ottawa. 



At the request of the writer, Mr. F. T. Shutt, chemist to the Dominion 

 experimental farms, has very kindly made two analyses of the Ottawa water, 

 taken at the Chaudiere falls, which face the city. The first sample was collected 

 on March 12, 1907, at a time when the river was still ice-covered and reported 

 to be at the lowest stage known in fifty years. The second sample was collected 

 on July 16, 1907, during the summer high-water period. Its analysis is more 



* lory's well known estimate of the age of the ocean as about 90,000,000 years seems 

 much too low for the needs of the geologists. His view that the sodium borne into 

 the ocean by the rivers during past time is nearly all represented in the present sea- 

 water is apparently one of the soundest in dynamic geology. The chief source of 

 doubt as to the validity of his method of calculation consists in the obvious fact that 

 it is not yet possible to secure even an approximate idea as to the secular variation 

 of the land area in size. The age of the ocean would be greatly increased if account 

 be taken of a relatively small area throughout much of pre-Cambrian time. To the 

 present writer, Joly's estimate is of value in suggesting that the pre-Huronian land 

 area was in reality small. 



