STRATIFIED AND UNSTRATIFIED ROCKS. 21 



occupy were at some former period the sites of lakes, estua- 

 ries, and seas. 



In a similar manner we seek to explain the origin and 

 nature of the basalts and greenstones that rise up in homo- 

 geneous masses, and not in layers or bed above bed. And 

 when we go to the volcano or burning-mountain, and ob- 

 serve the discharges of molten lava, which when cooled 

 assume a structure scarcely distinguishable from that of 

 the basalts and greenstones, we are equally entitled to 

 infer that these have originated like lava, and consequently 

 have been formed through and by the agency of fire ; hence 

 we regard them as igneous or volcanic if we refer to their 

 origin, and unstratified if to their mode of arrangement. 

 There are thus in the crust of the globe only two great 

 categories of rocks the aqueous or stratified, and the 

 igneous or unstratified ; the former produced through and 

 by the agency of water, the latter through and by the 

 agency of fire. The stratified, by the waterworn particles 

 of which they are composed, and their sedimentary arrange- 

 ment, layer above layer, give evidence of the forces that 

 operate from without ; the unstratified, by their crystalline 

 texture and the manner in which they break through and 

 derange the sedimentary strata, of the forces that exert 

 themselves from within. 



These two sets of rocks are being formed at the present 

 day the stratified or sedimentary in every lake, estuary, 

 and sea, and the unstratified or eruptive around every 

 active volcano. And, as nature's operations are incessant, 

 such rocks must have been formed during all time from 

 the current hour back through untold ages. Did the 

 watery forces rains, rivers, waves, tides, and ocean- cur- 

 rents alone prevail, the dry land would in course of time 

 be worn and wasted down to one uniform level, over which 

 the ocean might roll in uninterrupted continuity. But just 



