52 
ARCHDEACON PRATT ON THE EFFECT OP LOCAL ATTRACTION. 
down into the heavy fluid supporting it ; so must a deficiency of matter near the 
surface, in deep and wide oceans, imply an excess of matter below the ocean-bed, 
and therefore a protrusion of the heavy fluid up into the light crust. If this were 
not the case, the fluid below would by its greater upward pressure burst up the crust 
beneath the ocean, and this would lead to a catastrophe. 
Hence the thickness of the crust must follow this singular law, — that wherever its 
upper part is increased by rising into mountains and table-lands, its lower part is 
also increased by projecting downwards into the internal fluid ; and wherever, on the 
other hand, the upper part is diminished by sinking into ocean-beds, there also the 
lower part is diminished by the heavy fluid protruding into it. 
This law appears to be contrary to what we should expect from the process of 
cooling. 
Lausanne, October 8, 1855. 
