DEPOSITS OF SCOTLAND. 377 
eral history of the globe a connecting link between deposits 
considerably more than four thousand miles apart. I may add 
that, during the last few years, I have been able to place in my 
little museum, beside its Silurian fossils of America and Eng- 
land, a not less ample collection of the Silurian fossils of our 
own country, which, though still inadequate, contains several 
rare organisms, with which, so far as is yet known, the English 
deposits could not have supplied me. Still, however, much 
remains to be done in this curious field. I was shown only a 
few weeks ago, by a gentleman from the neighborhood of Les- 
mahagow, a fossil crustacean, derived, he said, from the Grau- 
wacke of that neighborhood, which, so far as I could judge, in 
its rather indifferent state of preservation, is new to Scotland, 
and which very considerably resembles that Hymenocaris of 
North Wales which Sir Roderick describes in his “ Siluria” as 
a true primordial fossil. And where the crustacean occurs, it 
is more than probable that other organisms will yet be found. 
The Lower Old Red Sandstone of Scotland has been more 
thoroughly wrought out than perhaps any of the other forma- 
tions of the country, and it occupies, in consequence, a larger 
space in my collection. I have not yet found fossils in the 
Great Conglomerate, which forms its base; nor, perhaps, could 
organisms, save of the most robust structure, be expected in a 
rock formed of great water-rolled pebbles, which, ere they could 
have assumed their present rounded forms, must have been 
tossed by the storms of ages. In the pebbles themselves, how- 
ever, we have curious glimpses afforded us of the old metamor- 
phic rocks of Scotland; which were, we find, considerably 
different in the group from the rocks of similar origin that in 
the present age of the world compose our great Highland nu- 
cleus. The schistose gneisses, now the prevailing metamorphic 
rocks of the kingdom,—for they occupy nearly ten thousand 
square miles of its area,—were then but feebly developed, 
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