ROCKS OF SCOTLAND. 831 
quarry, and, where unweathered, of a darker gray; and, as 
the organisms which it encloses yield more readily on expo- 
sure than the surrounding matrix, they exist upon the surface 
as mere darkened casts, but in the fresh fracture are of a pearly 
white. And here, also, trilobites and corals occur among the 
shells. <A little further on, the rock assumes yet a different 
hue; it abounds in iron, which imparts to it in some places a 
deep red, in others a buff-yellow hue; and the fossils, converted 
into a bright yellow ochre, present, when broken, an almost 
golden aspect, and are of great, though from their state of 
extreme oxidization, of short-lived beauty. I have rarely seen 
anything richer in appearance than the bright yellow trilobites 
on a deep red ground which I laid open in one of the higher- 
lying quarries of the hill. They reminded me of the trilo- 
bites in the collection of a certain noble lord, now deceased, 
who became eccentric as he grew old, and, to improve their 
appearance, got them gilded and burnished. Sheets of festi- 
nella of the same bright hue, that, when first exposed by the 
hammer, resemble pieces of gold lace, mingled with sprigs of 
golden coral, and deeply suleated golden petraia, also occur in 
great abundance; with bronze-looking shells by the million, 
chiefly of the genera orthus, atrypa, and terebratula. So 
thickly do these lie in some of the beds, as to give to the other- 
wise solid rock a fissile character. One of the most remaka- 
ble-looking fossils of the group, is, however, a large trilobite,— 
an Illenus, furnished with a caudal shield as large as that 
which covers its head, and of a decidedly Lower Silurian type, 
as are almost all the other accompanying organisms, though 
some of them have a wide range in the system, and occur in 
the lower beds of its upper division. I may mention, that I 
found here, at the height of many hundred feet over the sea, the 
boulder clay, with its characteristic pebbles scored and pol- 
ished, and in most cases bearing their striz in the line of their 
