142 The American Geologist. ^^''cii. i^oi- 
In the case of the vertical edges, however, the agreement 
in position, as well as direction, is exact. Precisely below the 
three corner blocks, there are three lines of instability coincid- 
ing with the vertical tetrahedral edges. Below the Canadian 
coign there is the line of the Andes (long. 75°), which, accord- 
ing to some geologists is still undergoing elevation. Almost 120" 
east of the Andes, and below the Scandinavian coign, is the 
Erythrean rift-valley (mean long. 40°), in which some of the 
earth-movements are unquestionably of very recent date. 
Again, nearh^ 120** eastward, and due south of the Manchurian 
coign, is the recent line of movement represented by the east- 
ern coast of Australia. 
The main mountain systems of the world correspond, then, 
in direction or position, or in both, with the edges of the tetra- 
hedron. The mountain lines run east and west in the northern 
hemisphere, and run meridionally in the southern hemisphere 
— that is, always parallel to the tetrahedral edges. 
But it will be said there are three great exceptions, for the 
Ural mountains, the Appalachians, and the Rocky mountains 
are meridional instead of transverse, and that they therefore 
contradict the scheme. The contradiction is only apparent. 
The existing mountain ranges date from two main periods of 
mountain-building — the Upper Cainozoic and the Upper Palae- 
ozoic. The Upper Tertiary system includes the Alps, Andes, 
Himalaya, Pyrenees, Caucasus, and Atlas, etc. The Urals, 
Rocky mountains, and Appalachians belong to the Upper 
Palaeozoic system. Before we can say whether these chains 
confirm or refute the tetrahedral theory, we must determine 
the distribution of land and water at the time wdien they were 
made. 
Now, we know that in upperPalseozoic times one land fauna 
and flora ranged round the southern hemisphere from Austra- 
lia to India, and thence to the Cape and South America. In- 
stead of there having then been a continuous ocean-belt sep- 
arating triangular points of land, there was then a southern 
land-belt, which was supported by three great equidistant cor- 
ner-stones, the Archean blocks of South Africa, of Australia, 
and of Patagonia and the Patagonian platform. 
What the south pole was doing then is hidden by our de- 
plorable ignorance of that area : but there is evidence that to 
