THE GEOLOGICAL HISTORY OF NEW YORK STATE 37 
plastic masses when subjected to any great lateral pressure within 
the earth.’ 
Rocks at the surface of the earth, subjected to the same laterai 
pressure, would be broken or fractured instead of bent or folded. 
It is not the present purpose to discuss the origin of such pressure 
within the earth, but suffice it to say that it is somehow due to the 
shrinkage of the interior portion of the earth, and the tendency of 
the exterior (or crust) to accommodate itself to the shrinking in- 
terior, thus producing lateral thrust (pressure) in this exterior 
portion. 
We are now ready to discuss the first known uplift of the whole 
Adirondack region above sea level, or what we may call the 
birth of the first known Adirondack mountains. As we have just 
learned, the very character and structure of the rocks now exposed 
in the region, show conclusively that they were at one time deeply 
buried under thousands of feet of overlying materials, and the 
inference is perfectly plain that those materials must have been 
removed by erosion. Extensive erosion of any land mass means 
that the land must be above sea level and thus we come to the 
important. conclusion that the great mass of Grenville sediments 
were upraised well above sea level. Just when the great uplift oc- 
curred can not be positively stated, but if it was not during, or after 
the igneous intrusions, it must have been shortly before them. It is 
quite reasonable to believe that the same great force which caused a 
welling up of so much liquid rock might easily have caused a decided 
uplift of the whole region. Again, it is quite plausible that there 
may have been no great uplift until the development of the lateral 
pressure which caused the metamorphism of the rocks. Still another 
view is that a lateral pressure, once started, first caused a welling up, 
at different times, of igneous rock and then, after the cessation of 
the igneous activity, the same force continued to compress, fold 
and metamorphose the rocks. Whatever the actual history may 
have been, it is at least true that the sum total of all effects, as we 
now observe them, harmonizes well with the view last expressed. 
The intense folding and tilting of the strata show that the amount 
of uplift must have been very considerable as is the case in all typi- 
cal mountain ranges. We can not, however, even state the approxi- 
mate height of those very ancient Adirondack mountains. The fact 
1Professor Adams of McGill University, Montreal, has recently proved 
experimentally that rocks, under great pressure, flow like plastic matter. 
