PROGRESSIVE INCREASE OF VISCOSITY 547 
If now this system be carried to its ultimate end what will 
result 2? Obviously the dips of the sedimentary strata will approach 
iG 
eee ee 
Fig 6 
Fics. s-9.—Series of diagrams illustrating the effect of marginal cooling and 
increasing viscosity on the curve of a laccolithic surface. 
the vertical, and if the central portion of the igneous mass is still 
competent to transmit pressure either by hydrostatic means or by 
direct thrust through a central core now become very viscous, it 
