20 THE CRUISE OF THE BETSEY ; OB, 



the greater part of which had been thus washed ashore in 

 handfuls, and ground down by the blended agency of the 

 trachyte and the surf. Once formed, however, in this way 

 it began to receive accessions from the exuviae of animals that 

 love such localities, the deep arenaceous bed and soft sand- 

 beach ; and these now form no inconsiderable proportion of 

 the entire mass. I found the deposit thickly inhabited by 

 spatangi, razor-fish, gapers, and large well-conditioned cockles, 

 which seemed to have no idea whatever that they were living 

 amid the debris of a charnel-house. Such has been the ori- 

 gin here of a bed of shell-sand, consisting of many thousand 

 tons, and of which at least eighty per cent, was once asso- 

 ciated with animal life. And such, I doubt not, is the his- 

 tory of many a calcareous rock in the later secondary forma- 

 tions. There are strata not a few of the Cretaceous and Ooli- 

 tic groupes, that would be found could we but trace their 

 beginnings with a certainty and clearness equal to that with 

 which we can unravel the story of this deposit to be, like 

 it, elaborations from dead matter, made through the agency 

 of animal secretion. 



We set out on our first exploratory ramble in Eigg an hour 

 before noon. The day was bracing and breezy, and a clear 

 sun looked cheerily down on island, and strait, and blue open 

 sea. We rowed southwards in our little boat through the 

 channel of Eilean Chaisteil, along the trap-rocks of the island, 

 and landed under the two pitchstone veins of Eigg, so gene- 

 rally known among mineralogists, and of which specimens 

 may be found in so many cabinets. They occur in an earthy, 

 greenish-black amygdaloid, which forms a range of sea-cliffs 

 varying in height from thirty to fifty feet, and that, from 

 their sad hue and dull fracture, seem to absorb the light ; 

 while the veins themselves, bright and glistening, glitter in 

 the sun, as if they were streams of water traversing the face 

 of the rock. The first impression they imparted, in viewing 



