586 



THE DISTRIBUTION, ETC., OF ALKALINE ROCKS, 



and has undergone differentiation, or it has mixed with other 

 magmas, chiefly basic, and then been differentiated. 



8. The age and mode of occurrence of alkaline rocks lend 

 support to the Laplacian (Gaseo-Molten) hypothesis of Cosmogony, 

 and seem difficult to explain on the planetesimal hypothesis. 



9. It is also suggested that great basic intrusions frequently 

 aided in the refusion and extrusion of alkaline schists and 



Legend. 



Cine o/ Outcrop of Alt aim e 

 Rotks -broken Line - 

 Late Hkozoic Cast 

 t \ Lite fhltoiott \ 



Seai, cretshotched £ 



Fig. 11. —Relation of the Line of Outcrop of Alkaline Rocks 



to the approximate Coast-line in late 1'alseozioc time (Devonian, 



Carboniferous, and Permian). 



magmas. The crushing of subsiding earth-blocks between passive 

 segments also aided the expulsion. 



10. Durocher's view of two principal magmas and Prior's 

 division of lavas into those of the Atlantic and those of the 

 ' Pacific ' type have been discussed and have been shown to be 

 favourable to the hypothesis advanced. 



