A SUMMER RAMBLE AMONG THE HEBRIDES. 173 



equivocal evidence of two great catastrophes which over wide 

 areas depopulated the seas. In the Old Red Sandstone of 

 Caithness there are many such platforms : storey rises over 

 storey ; and the floor of each bears its closely-written record 

 of disaster and sudden extinction. Pompeii in this northern 

 locality lies over Herculaneum, and Anglano over both. We 

 cease to wonder why the higher order of animals should not 

 have been introduced into a scene of being that had so re- 

 cently arisen out of chaos, and over which the reign of death 

 so frequently returned. In a somewhat different sense from 

 that indicated by the poet of the " Seasons," 



" As yet the trembling year was unconfirmed, 

 And winter oft at eve resumed the gale." 



Lying detached in the stratified clay of the fish-beds, there 

 occur in abundance single plates and scales of ichthyolites, 

 which, as they can be removed entire, and viewed on both 

 sides, illustrate points in the mechanism of the creatures to 

 which they belonged that cannot be so clearly traced in the 

 same remains when locked up in stone. There is a vast deal 

 of skilful carpentry exhibited if carpentry I may term it in 

 the coverings of these ancient ichthyolites. In the commoner 

 fish of our existing seas the scales are so thin and flexible, 

 mere films of horn, that there is no particularly nice fitting 

 required in their arrangement. The condition, too, through 

 which portions of unprotected skin may be presented to the 

 water, as over and between the rays of the fins, and on the 

 snout and lips, obviates many a mechanical difficulty of the 

 earlier period, when it was a condition, as the remains de- 

 monstrate, that no bit of naked skin should be exposed, and 

 when the scales and plates were formed, not of thin horny 

 films, but of solid pieces of bone. Thin slates lie on the roof 

 of a modern dwelling, without any nice fitting ; they are 

 scales of the modern construction : but it required much nice 

 fitting to make thick flag-stones lie on the roof of an ancient 



