Mr J. D. Dana on the Origin of Trap Minerals. 266 



taken up in a similar manner. But the rock itself has often 

 afforded the ingredients for the forming minerals, during 

 the passage of the filtrating fluid through it. By the same 

 means, the adjoining walls of a seam or dyke, which receive 

 the drainings from the rock of the dyke, are often penetrated 

 by zeolitic minerals. 



It may be thought that I am giving undue influence to a 

 favourite theory, and in the minds of some, these conclusions 

 may be set down among mere speculations in science. But 

 the circumstances attending submarine igneous action, I am 

 persuaded, is not generally apprehended. What is the con- 

 dition of the deep bed of an ocean \ Even at a depth of three 

 miles, the waters press upon the bottom with a force equiva- 

 lent to a million of pounds to the square foot ; and with such 

 a forcing power above, can we set limits to the depth to 

 which these sea-waters — magnesia and soda solutions — will 

 penetrate \ Will not every cavern, every pore, far down, 

 be filled, under such an enormous pressure % Let a fissure 

 open by an earthquake effort, and can we conceive of the 

 tremendous violence with which the ocean will rush into the 

 opened fissure \ Let lava ascend, can we have an adequate 

 idea of the effect of this conflict of fire and water \ The rock 

 rises, blown up with cavities like amygdaloid, and will a long 

 interval elapse before every air-cell will be occupied from the 

 incumbent water ? Suppose an Hawaii to be situated beneath 

 the waves, pouring forth its torrents of liquid rock ; — this 

 island contains about five thousand square miles, which is less 

 than the probable extent of many a region of submarine erup- 

 tion ; — suppose, I say, the fires were opened and active over 

 an area of some thousands of square miles — are there no 

 effects to be discovered of this action \ There is no geologist 

 that pretends to deny the premises — the fact of such submarine 

 eruptions, the ocean's pressure, the effect of fire in heating 

 water, and in giving it increased solvent power ; and why 

 should they not reason upon the admitted facts, and study 

 out the necessary consequences ? Surely, if there have been 

 effects, we might expect to see some of them manifested in 

 the cavities of the ejected rocks, which were opened at the 



