ARCHAEAN TIME. 159 



with serpentine. Eozoon has also been observed in Archaean rocks in Bavaria (named 

 E. Bavaricum), in Saxony, Bohemia, Hungary, and at Pargas in Finland. 



Profs. Wm. King and J. H. Rowney, of Dublin, hold that Eozoon is of mineral and 

 not of animal origin (Proc. Roy. Irish Acad, for 1869 and 1871) ; and others have urged 

 the same opinion. Doubts are excited by the fact that it resembles in structure forms 

 that are of mineral origin ; by the unequal thickness of the calcareous layers and the inter- 

 spaces ; and by the fact that serpentine of later formations has afforded similar forms. 

 H. J. Carter, by his research, is led to reject it ; Dr. Carpenter, by his, to sustain it. 



Forms resembling Annelid tubes have been stated by Dr. Fritsch to occur in the 

 Laurentian of Bohemia; and Dr. Dawson, from some obscure indications, has sug- 

 gested the "possible existence" of sea-worms or Annelids in the Canada Laurentian. 

 Whatever may be the final decision with regard to Eozoon, there can be little doubt that 

 Rhizopods existed in Archaean time. 



• 



2. HURONIAN PERIOD. 



Geographical Distribution, and Rocks. — The rocks first distin- 

 guished as Huronian lie over a region on the north coast of Lake 

 Huron, extending from a point a few miles west of French River 

 nearly to Sault Ste. Marie. The width is undetermined, but probably 

 it does not exceed ten or fifteen miles. They lie unconformably upon 

 the Laurentian rocks, showing that they are of subsequent origin ; 

 but they contain no fossils to fix precisely their age. Other smaller 

 areas occur on the north shore of Lake Superior. 



The rocks of the Lake Huron region include greenish siliceous 

 slates and conglomerates ; quartzytes ; layers of jasper and chert ; 

 hard quartz and jasper conglomerates ; thin layers of grayish or blue- 

 ish limestone ; and also beds of dioryte, which in some places graduate 

 into syenyte, and in others contain epidote. The strata of quartzyte 

 and conglomerates are from 1,000 to 2,500 feet thick. The latter con- 

 tain stones (some a foot in diameter) that were derived from the 

 Laurentian. Some of the sandstone layers are ripple-marked. The 

 limestones contain none of the minerals common in this rock in the 

 Laurentian. 



The strata are much intersected by dikes of dioryte ; and it has 

 been questioned whether the beds of dioryte were not injected beds. 

 There are also large numbers of veins bearing copper ores (sulphids 

 chiefly), which intersect the dikes of dioryte, and are therefore the 

 later in orio-in. 



Besides the above-mentioned regions of Huronian rocks, there are others which are 

 referred to this period mainly on lithological grounds, — chloritic rocks, dioryte, felsitic 

 (porphyroid) rocks and epidotic rocks being regarded as especially characteristic of 

 the Huronian. 



Of these are: (1) In Michigan, the large area, south of Lake Superior, in which lie 

 the immense iron-ore beds of Marquette, already mentioned (p. 151). The rocks are in 

 part dioryte, chlorite schist, beds of jasper and chert. As it is not certain that such an 

 association of rocks may not have been formed in other eras, and even in the Lauren- 

 tian, the evidence as to age is far from conclusive. The extent of the beds of iron-ore 

 affords some reason for believing, as shown by Whitney, that they are true Laurentian. 



