90 SMITHSONIAX MISCELLANEOUS COLLECTIONS VOL. 64 



tionate amount have varied in the river waters of Algonkian time, 

 but probably it was essentially similar in composition and larger in 

 quantity. 



Constituents. Tons in a Cubic Mile. 



Calcium carbonate (CaCOa) 326,710 



Magnesium carbonate (MgCOs) 112,870 



Calcium phosphate (CasPsOs) 2,913 



Calcium sulphate (CaSd) 34,361 



Sodium sulphate (Na2S04) 31,805 



Potassium sulphate (K2SO4) 20,358 



Sodium nitrate (NaNOs) 26,800 



Sodium chloride (NaCl) 16,657 



Lithium chloride (LiCl) 2,462 



Ammonium chloride (NHiCl) 1,030 



Silica (SiOs) 74-577 



Ferric oxide (Fe20s) 13,006 



Alumina (AI2O3) 14,315 



Manganese oxide ( MnoOa) 5,703 



Organic matter 79,020 



Total dissolved matter 762,587 



Many authors have written on the limestone-fomiing algge that 

 should be referred to in a memoir on the subject, but in this prelim- 

 inary paper on the Algonkian forms of the Cordilleran area only a 

 few will be noticed. 



In a recent paper on " Th-e Important Part Played by Calcareous 

 Algae at certain Geological Horizons " ^ Professor E. J. Garwood 

 gives a brief historical account of the genera and then discusses 

 the influence of algae in the formation of sedimentary rocks. He 

 mentions the presence of oolites in the Archean and Algonkian 

 rocks.'' Very few traces have been found in Cambrian rocks, but 

 in the Ordovician they become much more abundant. He does not 

 mention the Cambrian genus Cryptozoon. After reviewing the 

 algae of geologic time Professor Garwood concludes that it plays 

 a very important part as rock builders at many dififerent horizons 

 in the geologic series ; that certain forms are restricted to definite 

 geologic periods, but that they had a wide geographic range. He 

 calls attention to the co'ustant association of fossil calcareous algae 

 with oolitic structure and also with dolomite. In regard to the 

 latter he says : ' 



The presence of dolomites in connection with algal growths at different 

 geological horizons appears to show that the beds have accumulated under 



^ Geol. Mag. n. s., Dec. 5, Vol. 10, 1013,- pp. 440-446, 490-498, 545-553. 



" Idem, p. 491. 



^ Idem, pp. 0^2-5^2,- 



