Prof. J. Le Conte — Permanence of Continents, etc. 99 



but not generally recognized. The evidence of this fact is found in 

 the eroded condition, universal so far as known, of the Archaean 

 rocks underlying all other rocks, even the lowest primordial. No 

 one has ever seen conformable relation between the Archaean and any 

 other later rocks. Not only is this unconformity found all about the 

 border of the Canadian Archaean area and the Appalachian area and 

 about all the smaller areas in the most widely separated parts of the 

 continent, but the grand Canon of Colorado cuts through the whole 

 stratified series and into the Ai'chaean exposing the line of contact, 

 and we find the same unconformity ; the St. Louis Artesian pierces 

 the whole Palaeozoic, and again from the sudden change in the 

 character and condition of the rocks from unmodified into metamor- 

 phic, we must conclude unconformity. But unconformity means 

 eroded land surface. Therefore we must conclude that well-nigh 

 the whole continent was land at the end of the Archaean. It is 

 almost certain therefore that at the end of the Ai'chaean, there was 

 a veritable exchange of sea and land, and that the North Atlantic 

 Archaean continent became sea at that time. If so, the strata which 

 were then formed, and of which the eroded surface of Archaean rocks 

 is the sign and measure, are now beneath the sea, and therefore irre- 

 coverably lost. This period between the Archaean and the Primor- 

 dial I have elsewhere 1 called the "Lost Interval," because we have 

 no record of it in the stratified rocks. 2 Judging by the amount of 

 erosion of Archaean rocks, and also by the prodigious advance in the 

 progress of life when the record commences again in the Primordial, 

 this lost interval must have been a period of immense duration. 

 There are in the history of the earth many other intervals, partially 

 or locally lost, represented by local unconformities, the most im- 

 portant of which occurred at the end of the Palaeozoic ; but none of 

 these are to be compared with that which occurred at the end of the 

 Archaean. 



3. The Palaeozoic commenced with another large crust-movement, 

 but not a complete interchange of sea and land as before. The 

 American continent was again largely, but not completely submerged. 

 It went down until only the now-known Archaean areas, together 

 with an eastern area of unknown size now covered by the sea, were 

 left. The continent then consisted of a large V-shaped land-mass 

 corresponding to the well-known Canadian Archaean area, a large 

 eastern land-mass, including the Appalachian Archaean area, but 

 extending eastward at least as far as the submerged continental 

 border, and a large mass in the Eocky Mountains, and especially in 

 the Basin region, while a great interior continental sea occupied the 

 position of the drainage basin of the Mississippi river. The so- 

 called map of Archaean land of Dana and Chamberlin would repre- 

 sent approximately the condition of things at this time, if the eastern 

 border-land were extended as far as the submerged continental 



1 Am. Journ. Science, 1877, vol. xiv. p. 101. Le Conte's Elem. of Geol. p. 291. 



2 Some intermediate rocks have been found, e.g. the Kewenawan series, but the 

 gap is still immense. 



