158 



R. A. DALY THE EVOLUTION OF TH£ LIMESTONES 



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 represented 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 complete than that of 

 the first sample. The two gave results shown in columns 1 and 2 of 

 table II. 



Table II. 



Total solids at 98-100° centigrade. 



Loss on ignition 



Solids after ignition 



Si0 2 ... 



Al A . 



FeA.. 

 MgO . . 

 CaO... 

 Xa 2 0. . 

 K 2 0... 

 SG 3 . . . 

 Mn 3 4 . 



PA-,. 

 CI.... 



Low water. 



Parts per mifliot 



54.66 

 24.03 

 30.63 



6.52 

 .38 

 .34 

 3.87 

 12.57 

 not det. 

 not det. 

 3.70 

 not det. 

 not det. 

 not det. 



High water. 



Parts per million. 

 46.07 

 15.74 

 30.33 



7.06 



.52 



.70 

 2.77 

 8.18 

 2.14 



.67 



2.51 



• .86 



.43 



.50 



Five sanitary analyses of the Ottawa river water have been made by 

 Mr Shutt. The samples were taken on the following dates : December 

 22, 1887; October 18, 1898; December 7, 1898; May 8, 1899, and August 

 22, 1905. These analyses gave, respectively, total solids at 53.0, 55.6, 



