RAMBLES OF A GEOLOGIST. 365 



tial in their effects, is curiously suggestive of the old meta- 

 physical idea, that as every effect has its cause, " recurring 

 from cause to cause up to the abyss of eternity, so every cause 

 has also its effects, linked forward in succession to the end of 

 time." On the bleak moor of Culloden the graves of the 

 slain still exist as patches of green sward, surrounded by a 

 brown groundwork of stunted heather. The animal matter, 

 once the nerves, muscles, and sinews of brave men, which 

 originated the change, must have been wholly dissipated ages 

 ago. But the effect once produced has so decidedly main- 

 tained itself, that it remains not less distinctly stamped upon 

 the heath in the present day than it could have been in the 

 middle of the last century, only a few years after the battle 

 had been stricken. 



The vitrification of the rampart which on every side in- 

 closes the grassy area has been more variously, but less satis- 

 factorily, accounted for than the green luxuriance within. It 

 was held by Pennant to be an effect of volcanic fire, and that 

 the walls of this and all our other vitrified strongholds are 

 simply the crater-rims of extinct volcanoes, a hypothesis 

 wholly as untenable in reference to the hill-forts as to the 

 lime-kilns of the country : the vitrified forts are as little vol- 

 canic as the vitrified kilns. Williams, the author of the 

 " Mineral Kingdom," and one of our earlier British geolo- 

 gists, after deciding, on data which his peculiar pursuits en- 

 abled him to collect and weigh, that they are not volcanic, 

 broached the theory, still prevalent, as their name testifies, 

 that they are artificial structures, in which vitrescency was 

 designedly induced, in order to cement into solid masses accu- 

 mulations of loose materials. Lord Woodhouselee advocated 

 an opposite view. Resting on the fact that the vitrification 

 is but of partial occurrence, he held that it had been pro- 

 duced, not of design by the builders of the forts, but in the 

 process of their demolition by a besieging enemy, who, find- 



