TETRAHEDROID TENDENCY IN FORMATION OP EARTH'S CRUST 69 



waters has diminished the Arctic sea and the Antarctic land in exact 

 proportion. The mathematical centers of the four oceans are equidis- 

 tant from each other, s}^mmetrical with the four depressed centers of the 

 model. I have been interested to see the similarit}^ between the land 

 masses as a whole and the ocean areas as given by Gilbert* in his sug- 

 gestive u orange-peel projection." This is drawn at the true continental 

 borders, making the elevated and depressed areas about equal, as they 

 should be for comparison. 



We may now examine in order the series of paleographical maps 

 (plates 10 and 11), very hypothetical, of course, the first five taken mainly 

 from de Lapparent, the last three from Koken,f and sej3 what traces of 

 the tetrahedroid condition appear in the past. 



In the first map, taken from de Lapparent,! which shows (plate 10, a) 

 the present Archean areas on the globe, if we omit the areas which have 

 been brought up from great depths by folding, the remainders arrange 

 themselves in three groups which occupy closely the position of nuclei 

 of the three tetrahedral continents. I have drawn lines on the map 120 

 degrees apart to show their symmetrical positions. One may compare 

 with this Green's maps, given as figure 1 on plate 9. 



At the northern apices of these hypothetical continents are, first, the 

 Canadian shield of Suess or protaxis of Dana, with the shallow water- 

 cover of Hudson bay ; second, the Scandinavian shield of Suess, or boss, 

 as Adams has proposed to call these ancient lands. It is partly covered 

 by the shallow Baltic sea. Third is the Manchurian shield of Gregory, 

 or coign, as he would call it, partly covered by the shallow Okotsch sea. 

 Nearly south of each is the southern apex of these embryo continents — 

 the Archean nucleus of Australia, the highlands of Guyana, and the 

 African Archean tableland. Finally, the Antarctic continent is prob- 

 ably Archean, as the boulders from its icebergs show. 



If we consider the great mass of the sedimentary strata which has been 

 derived by erosion from these old lands which were folded and worn 

 down in pre-Cambrian times, the fact that they still rise high above sea- 

 level suggests some such constantly working force of upheaval acting upon 

 them as the tetrahedral hypothesis demands. These are the primeval, 

 immovable corner stones of the earth, against which the waves of an- 

 cient seas have broken, while they have remained, in part, perhaps, 

 always unsubmerged, and against which mountain ridges have been 

 pressed and broken down like waves of the sea. 



*G. K. Gilbert: Continental problems. Bull. Geol. Soc. Am., vol. 5, p. 185. 

 f E. Koken : Die Vorwelt, 1893, p. 1. 

 | Traite de Geologie, 1900, p. 739. 



X— Bull. Geol. Soc. Am., Vol. 11, 1899 



