654 



DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 

 Table XL. — Calcium and magnesium in various rivers. 



Ri\ 



Terrane. 



Ottawa — 



a. Low water 



b. High water 



c. Mean of a and b . 



d. Sainte Anne ... 



Average of four Swedish rivers 



and Ottawa and Pigeon rivers. 

 Saint Lawrence at Ogdensburg — 



average of 6 monthly analyses. 

 Mississippi— 



a. At Minneapolis — average of 

 23 analyses. 



/;. Memphis — analyses of 17 com- 

 posites. 



c. New Orleans — average of 52 

 composites. 

 Danube — average of 23 analyses. 



Rhone — average of 5 analyses 



Seine 



Average of 19 rivers (Murray)*.. . . 

 Average of 44 rivers 



Late pre-Cambrian 



Late pre-Cambrian and early 



Paleozoic . 

 Late pre-Cambrian 



Late pre-Cambrian and Paleozoic 



Late pre-Cambrian and early 



Paleozoic. 

 Late pre-Cambrian and Paleozoic 



chiefly. 

 Nearly average continental mass 



of present time. 



ditto 

 ditto 



Calcium. 



Parts per 

 million . 



8-98 

 5-84 

 741 

 992 



6-88 



32 05 



41-18 

 34 38 

 33 90 



43 89 



44 91 

 73 99 

 33-85 

 37 77 



Magne • 

 sium. 



Parts per 

 million. 



235 

 1-67 

 201 

 202 



152 



7-21 



15 34 



13-75 



8 65 



Ratio of 

 Ca to Mg 



•94 



•22 

 •60 



•75 

 03 



350 

 382 

 369 

 491 



452:1 

 444 : 1 



269 : 1 

 250 :1 



392:1 



442 



7-22 



46 24 



437 



418 



* Sir John Murray: Scottish Geographical Magazine, Vol. 3, 1887, p. 65. 



Comparison of the Ottawa and other Rivers. 



The Ottawa carries past Ottawa city only 23 per cent as much calcium per 

 volume as the Saint Lawrence river carries past Ogdensburg, and less than 20 

 per cent as much calcium per volume as the Mississippi carries past Minneapolis. 

 About one-third of the Saint Lawrence basin is occupied by the Great lakes, in 

 which area probably very little solution of calcium salts is taking place. Another 

 large part of the basin is occupied by the pre-Cambrian terranes where highly 

 calcareous rocks are relatively rare. The content of this river is therefore less 

 than it would be if the river basin were all occupied by the average rocks of the 

 whole continental area of the earth. The comparison of these three rivers is 

 specially instructive, since they are all working under essentially similar climatic 

 conditions, with nearly the same ratio of rainfall to run-off. From the compari- 

 son it seems probable that, if the continents were all of their present size and 

 composed of rocks typical of the lands during the late pre-Cambrian, the rivers 

 would deliver to the sea annually not more than one-fifth as much calcium as is 

 carried by the existing rivers of the continents. 



This conclusion becomes more convincing when the Ottawa water is com- 

 pared with the other rivers noted in Table XL. 



In Clarke's admirable compilation of river analyses those referring to 

 rivers which drain pre-Cambrian terranes throughout their respective basins 



