BLOMIDON TO BRIAR ISLAM). 93 



matters, now form the thick bed of amygdaloid and tufa intervening 

 between the columnar trap and the red Bandstone. This is precisely 

 ■what we rind to be the case in modern volcanic eruptions. The first 

 violent explosions in such cases usually eject immense quantities of 

 dust and fragments of old lavas, which are blown or ejected to great 

 distances, or if they fall into the sea, as was most probably the case at 

 Blomidon, arc scattered in layers over its bottom. Over these ejected 

 scoria^ and ashes the lava currents which issue subsequently are poured. 

 We need not be surprised that we do not now perceive any regular 

 volcanic mountain or vent at Blomidon, for independently of the action 

 the waters may have exerted on it when being formed, we know that 

 great denudation has taken place in the Drift period, and under the 

 wasting action of the present frosts and tides. The minerals mentioned 

 as occurring in the trap are all either silica or silicates, — that is, com- 

 pounds of silica with the alkalies potash and soda, or the earths, as 

 alumina, lime, etc. They are produced by the solvent action of water, 

 which, percolating through the trap, dissolves these materials, and re- 

 deposits them in fissures and cavities. Below the amygdaloid, we 

 have a thick series of beds of red sandstone — mechanical detritus de- 

 posited by water, and probably in great part derived from the 

 waste of the sandstones of the Carboniferous system. The gypsum 

 veins which traverse it were probably deposited by waters which had 

 dissolved that mineral, in passing through the great gypsum-beds 

 which occur in the older system last mentioned. 



The history of this fine precipice is then shortly as follows. In the 

 Triassic era, thick beds of sandstone were deposited off the coasts of 

 Horton, just as the red mud and sand of the flats are now deposited. 

 Volcanic phenomena on a great scale, however, broke forth from 

 beneath the waters, scoriae and dust were thrown out, and spread 

 around in thick beds, and currents of lava were poured forth. Subse- 

 quently the whole mass was elevated, to be again submerged under 

 the boulder-bearing sea, by which, and the present atmospheric and 

 aqueous agencies, it was worn and wasted into its present form. Still 

 the work of decay goes on ; for yearly the frosts loosen immense 

 masses from its brow, and dash them to the beach, to be removed by 

 the ice and the tides, and scattered over the bottom of the bay. The 

 rains and melting snows also cut huge furrows down its front. These 

 agencies of destruction as yet, however, only add to the magnificence of 

 this noblest of all our sea-cliffs. The dark basaltic wall crowned with 

 thick woods, the terrace of amygdaloid, with a luxuriant growth of 

 light green shrubs and young trees that rapidly spring up on its rich 

 and moist surface, the precipice of bright red sandstone, always clean 



