16 
THE GEOLOGIST. 
thus lashed into fury by the winds, it may suffice to mention one fact, 
which is not in itself devoid of geological interest, inasmuch as it 
may serve to explain the occasional appearance of large blocks of 
stone in unexpected localities. In passing along Broad Sound from 
the south-east, there is an island called Great Crebawethan, which is 
probably in some way more exposed than others to this oceanic force. 
At any rate, there it is to be witnessed, standing probably eighteen 
or more feet out of the surface of the deep, at the highest spring- 
tides, with large boulders of granite, from half a ton to two tons 
weight, heaped upon its surface, as though the ballast of a dozen 
vessels had been discharged there by the hands of man, every 
stone of which, as I was assured by Mr. E. Douglass, the intelligent 
superintendent-engineer of the Bishop's Lighthouse works, has been 
raised to its present position, and deposited there, by the force of 
the waves.* The total destruction, too, of the iron lighthouse upon 
the Bishop's Rock, which, when near completion, was instantaneously 
uprooted, and dashed into the sea, on the night of February 5th, 
1850, may serve to convey an impression of the violent force to 
which the sides of tlie islands facing the Atlantic lie exposed ; and 
this will explain how it is that, when viewed in this direction, they 
appear rugged, precipitous, and excavated into caverns and ga^^s, while, 
approached from the eastern side, they lie smiling in the sun like 
fairy lands, or like the islands of the ^gean transplanted to our 
hyperborean shores. 
As the geologic features of St. Mary's are more or less repro- 
duced on a smaller scale in the other islands, I shall now proceed 
to give a detailed account of its most important characteristics. It is 
an irregular-shaped elliptical island, having two peninsulas attached, 
one to the lower, or western, extremity — viz., the Hugh, now 
fortified for a garrison, on the isthmus of which Hugh Town, the 
capital of the Scilly Islands, is built ; and the other at the extreme 
end, south of the island, terminating in the bold promontory of 
Peninnis Head, which is surrounded by Path Cressa Bay, the Atlantic 
Ocean, and Old Town Bay. The surface of the island is very various, 
* Mr. Douglass also informed me that, wlien lodging on Rosevear island, to 
superintend the works connected with tlie BLsliop Lighthouse, he had known 
blocks of granite twenty tons in weight to be moved some distance by the sea. 
