i894. CONTINENTAL GROWTH. 297 



tions consisting of lacustrine and fluviatile deposits, showing 

 that the estabhshment of these land-areas dates from a very early 

 time. 



The history of these Cretaceous and Tertiary areas is one of 

 both maturity and decay. They are in some portion of the latter 

 stage now, and eventually will probably give place to new land-areas 

 formed out of rocks now being constructed in the sea-beds from their 

 own dissolution. 



LiTHOLOGic Characteristics and Differences of the Rock- 



GROUPS OF SOME OF THE GrEAT PeRIODS. 



It is a remarkable fact, but no less true, that there are not only 

 palaeontological homologies running through the rocks of the Tertiary 

 group over the known world, but lithological analogies also. There 

 are diversities truly, but similarities also. Though conditions are 

 recurrent through the ages, as pointed out so strongly by the late 

 Sir Andrew Ramsay, it is recurrence with a difference. There has 

 been lithological evolution as well as organic. 



When we go further back in the world's history and consider 

 the rocks constituting the Carboniferous formation, the persistence 

 of characteristics over large areas of the earth's surface is most 

 •striking. The repetition of coals, sandstones, and shales in the 

 Carboniferous of the North- American Continent and in that of Great 

 Britain seems almost to point to a common origin. They repose 

 upon great limestone formations, indicating deep-sea conditions. The 

 ■coal formations in both countries indicate, according to all reliable 

 observers, a gradual sinking of the earth's crust and simultaneous 

 building up of the land by sediments of sand and mud, so that 

 successive terrestrial growths and land-surfaces are marked by each 

 bed of coal, excepting indeed in those cases that may arise from 

 floating vegetation gradually getting water-logged and sinking onto an 

 estuarine floor. These long-prevailing conditions are represented 

 by thousands of feet of rocks. It is evident from the lithological 

 resemblances, the occurrence of minerals in the same form and from 

 similar orders of succession, that the physiographic conditions pro- 

 ducing them were of world-wide extent and vast continuance. The 

 character of the flora was the same in the arctic as in the temperate 

 regions, and doubtless the maintenance of similar geographic con- 

 ditions was one element in this result. 



If, again, we cast our eye over the description of the Trias of 

 Great Britain and that of the United States, the same characteristics 

 occur in both. They are not at all like the Carboniferous, which they 

 succeed through the Permian phase ; yet, though the broad 

 Atlantic now divides them, they indicate like physiographical 

 conditions — strange to say, they are even of tlie same colour, 

 deep red and grey, and the characteristic fossils are footprints of 

 reptiles. Red sandstone, red and grey marls, and beds of salt 



