ARCH^AN TIME. 455" 



and named E. Bavaricum; also from Saxony, Bohemia, Hungary, and Pargas in Finland. 

 The specimens of Eozoon were first supposed to be Stromatopora corals (Logan's Rep. 

 Geol. Can., 1863, page 49), and afterward announced as Rhizopod in structure by Dawson ; 

 and this conclusion has since been sustained by W. D. Carpenter and others. But Eozoon 

 specimens have also been examined microscopically by good observers, among them King 

 ^nd Rowney, and Mobius, who have not found the supposed foraminiferal characters. 

 Quite recently, in 1891, the Tudor specimens were examined by J. W. Gregory with this 

 conclusion. 



Doubts are excited also by the close resemblance in structure to specimens that are of 

 mineral origin ; by the unequal thickness of the calcareous layers and the interstices ; and 

 by the fact that serpentine of later formations has afforded similar forms. It is objected 

 to on the ground that this mineral is often minutely interlaminated with fibrous serpentine 

 or some other mineral, showing that the soft amorphous material, as it solidified, sometimes 

 ■contracted and divided into thin laminae, leaving spaces between to receive depositions of 

 any kind ; in the Eozoon the infiltrating material was usually calcareous. 



Kotwithstanding the imperfection of the evidence, the existence of 

 E-hizopods and other Protozoans before the close of Archsean time is gen- 

 erally believed. 



The calcium phosphate (apatite) of the rocks, which is common in some 

 limestones, is also supposed to be of organic origin, because a constituent of 

 organic tissues and of some shells. Its abundance also in the iron ores 

 favors this view, inasmuch as the beds of ore are believed to be marsh pro- 

 ductions. But the phosphate is distributed in grains through many igneous 

 and other crystalline rocks, and the evidence may only prove that it was 

 present in solution in the sea-waters of the era. 



Above the grade of Protozoans, the type which is most likely to have 

 existed in the later Archaean is that of Rotifers ; for there is good reason for 

 believing, as stated on page 423, that from this group passed off independent 

 successional lines of species to Worms, Limuloids, Crustaceans, and terres- 

 trial Arthropods, and probably also to Bryozoans, Brachiopods, and perhaps 

 other tribes. 



ECONOMICAL PRODUCTS. 



The chief economical products of the Archaean terranes are : (1) Gold, 

 platinum, diamond ; (2) Iron ores ; (3) Copper, and other ores ; (4) Corun- 

 dum or emery ; (5) (j-raphite ; (6) Architectural materials, especially granite 

 and marble ; (7) Apatite or calcium phosphate for fertilizing purposes ; (8) 

 Feldspar for porcelain-making ; (9) Mica for the doors of lanterns, stoves, 

 etc., and various other uses ; (10) Zircon and monazite. 



The iron ores are among the most valuable. They sometimes contain too 

 much titanium ; and occasionally the proportion of disseminated grains of 

 apatite affects their value. This mineral may be distinguished by its green- 

 ish or grayish color and by its being soft enough to be scratched by the point 

 of a knife-blade. The American corundum (AI2O3) comes mostly from North 

 Carolina and Georgia. A mass weighing 400 tons was formerly obtained in 

 the rocks of Chester County, Pennsylvania. The mineral is ground up and 

 used for emery, it being the same compound as emery, but in a purer form. 



