160 akchjean time. 



The iron-ore, unlike that of northern New York, is specular iron-ore (Fe 2 3 ). But it 

 contains in many places octahedral crystals, which appear to indicate that it was once 

 magnetic iron-ore, and therefore that originally the ore of the two regions was alike. 

 H. Credner refers part of the region to the Laurentian, but retains the Marquette por- 

 tion in the Huronian. He states, that he observed an example of unconformability be- 

 tween the two systems of beds. They are also stated to be unconformable by Brooks 

 and Pumpelly. 



(2.) Other regions of rocks supposed to be Huronian occur in Newfoundland, New 

 Brunswick and some parts of New England ; in most cases they have been determined 

 only by the valueless test — the nature of the rocks. Credner refers to the Huronian, 

 with no better reason, a range of rocks along the whole course of the Appalachians, 

 from Canada to South Carolina; and he so calls certain auriferous rocks of Montgomery 

 County, North Carolina, which Emmons refers to the Taconic system, including hydro- 

 mica schist, quartzytes, itacolumyte or flexible sandstone, etc. Emmons found in one 

 of the beds a fossil-like form, which he pronounced a silicified coral and named Palxzo- 

 trochis (Am. Jour. Sci., II. xxii. 389); but, according to Hall and Marsh, it is probably 

 only a concretion. 



As the original Huronian has no fossils, there is no basis for a satisfactory determina- 

 tion of its equivalents. It is quite possible that it is Cambrian or Primordial. 



3. GENERAL CONCLUSIONS. 



Relations of the North American Archaean areas to the Conti- 

 nent. — On the map, p. 149, the striking fact is shown that the great 

 northern Y-shaped Archaean area of the continent ha>s (1) its longer 

 arm, B B, parallel approximately to the Rocky Mountain chain and 

 the Pacific border ; and (2) its shorter, C C, parallel to the smaller 

 Appalachian chain and the Atlantic border. Further : Of the other 

 ranges of Archaean lands, (1) there is one near the Atlantic border, 

 in Newfoundland, Nova Scotia, and New England ; (2) another along 

 the eastern side of the Appalachian chain ; (3) two or more, of great 

 length, along the Rocky Mountain chain ; and (4) others, not included 

 in the above, lie in ranges parallel to these main courses. Moreover, 

 the Archaean rocks of these regions were upturned and crystallized 

 before the Silurian age, and probably at two or more different epochs ; 

 and some, if not all, were thus early raised into ridges, standing not 

 far below the water's surface, if not above it. 



Hence, in the very inception of the continent, not only was its gen- 

 eral topography foreshadowed, but its main mountain chains appear to 

 have been begun, and its great intermediate basins to have been de- 

 fined — the basin of New England and New Brunswick on the east; 

 that between the Appalachians and the Rocky Mountains over the 

 great interior ; that of Hudson's Bay between the arms of the north- 

 ern V. The evolution of the grand structure-lines of the continent 

 was hence early commenced, and the system thus initiated was the 

 system to the end. Here is one strong reason for concluding that the 

 continents have always been continents ; that, while portions may 

 have at times been submerged some thousands of feet, the continents 



