EMERSON— RECURRENT TETRAHEDRAL DEFORMATIONS. 449 



and West Indian Seas, he assumes that the equator once went 

 parallel with this band and about io° south of it, with the north pole 

 at Behring's Straits and the axis at right angles to the ecliptic. Then 

 a band on either side of this equator including " the zone of the 

 intercontinental seas " or of the above three Mediterraneans, because 

 of the powerful tidal influence in the early ages, would be a zone of 

 distortion and rupturing during the crust-forming period and of 

 weakness since. This is Lowthian Green's twinning plane. ^ The 

 author follows Green also in assuming that in addition to this 

 equatorial flood-tidal fracture zone and at right angles to it would 

 run a meridional ebb-tidal fracture zone, which would pass through 

 the two points where the old and new equators bisect each other and 

 would be the meridian bordering the Pacific and including Australia 

 and Antarctica. 



This equatorial fracture zone he takes to explain the Mediter- 

 ranean zone and the transverse fracture zone to explain the per- 

 manence of the Pacific. 



For the establishment of this position he cites that part of the 

 reviewer's article on the tetrahedral earth- where Green's theory is 

 explained at length but not accepted. The later postulate of the 

 author that the earth has many times taken the tetrahedral form, 

 collapsed, and become again so rigid that it could again suffer tetra- 

 hedral deformation would seem to militate against a continuous in- 

 heritance of weakness in this region. 



The zone of fissuring remained a plane of weakness and the 

 greater elevation of the northward parts of the three triangular land 

 masses or coigns, or " shields " bringing them to move in a longer 

 circle and so to lag behind, caused a westward torsional motion of 

 these three portions of the coigns as compared with the parts south 

 of the aforesaid zone. 



The author accepts the suggestion first made by the reviewer^ 

 that the depressed ocean bottoms brought by sinking to move along 

 shorter radii must exert pressure against the west sides of the con- 



1 T. Lothian Green, " Vestiges of a Molten Globe," Honolulu, 1875, Pt. 

 II, 1887. 



2 " The Tetrahedral Earth and the Zone on the Intercontinental Seas." 

 Pres. Add., Bui. Geo. Soc. of Am., Vol. II., 1900. 



3 Loc. cit., p. 65. 



