VOLCANIC PHENOMENA. 



though Lough Keagh were the result of a post- Adamite sinking of 

 the ground. 



" On Lough Neagh's banks as the fisherman strays, 



When the clear cold eve's declining, 



He sees the round towers of other days 



In the wave beneath him shining ! 



Tli us shall memory, often, in dreams sublime, 

 Catch a glimpse of the days that are over ; 



Thus, sighing, look through the waves of time 

 For the long faded glories they cover !" MOOKE. 



125. It appears, then, that the crust of the earth, instead of 

 being endowed with that character of stability and immobility 

 popularly ascribed to it, is subject to incessant as well as occa- 

 sional upheavings and depressions. It may indeed be regarded aa 

 in a certain degree elastic, yielding to the undulations, whether 

 slow and gradual, or sudden and more violent, of the agencies 

 within it. 



Such phenomena, however, will cease to astonish when we 

 reflect what an enormous disproportion exists between the thick- 

 ness of the solid crust of the globe, and the mass of matter in a state 

 of igneous fusion which it encloses ; the crust being relatively" 

 thinner than a piece of card-board attached to the rind of an 

 orange, it cannot be matter of surprise that it should be subject to 

 more or less derangement of form, and even occasional disruption, 

 by the action of the fluid matter within it. That such changes 

 and such disruptions and their consequences should be much more 

 considerable at earlier than at more recent epochs, is also a 

 natural consequence of the growth of the crust of the globe by 

 the process of cooling. The earlier the epoch the thinner that 

 crust must have been, and the less its resistance to internal force. 

 Forces which would now fail to produce any sensible effect upon 

 its form, would at those earlier epochs have been sufficient to 

 disrupt it. That such effects have been actually produced at 

 various geological epochs is proved by the most incontrovertible 

 evidence presented by the crust of the globe itself, as will pre- 

 sently be more fully explained. Volcanic phenomena are closely- 

 connected with those of earthquakes, and, like them, supply 

 analogies by which various geological phenomena are explained. 



126. "When the crust of the earth is disrupted in the manner 

 explained above, openings are made in it which supply communi- 

 cation between its internal fluid nucleus and its external surface, 

 and through these openings matter of various forms is often ejected 

 with vast force. The matter thus ejected consists sometimes of 

 the disrupted and broken parts of the crust itself, which are 

 projected upwards, vertically or obliquely as the case may be, 



95 



