124 THE lîEITISH ISLES. 



guishes this beach ; it is equally regular with respect to the arrangement of the 

 materials of which it is composed. Its pebbles increase in size as we proceed 

 from west to east. The sand in the west almost imperceptibly passes over into 

 pebbles, and in the vicinity of the Isle of Portland these latter give place to 

 shingle. The fishermen along the coast will inform you that when they land on a 

 dark night on any part of the beach they can tell, from the size of the pebbles, at 

 what spot they find themselves. The true explanation of the phenomenon is 

 this : the tidal current runs strongest from west to east, and its power is greater in 

 the more open channel, or farthest from the land, while the size of the fragments 

 which are carried to the east and thrown ashore is largest where the motion of 

 the water is most violent.* 



To geologists the Isle of Portland offers a peculiarly interesting field of 

 research, for it is rich in dirt beds containing organic relics of marine origin, 

 and still exhibits the fossilised remains of a forest which flourished on the 

 emerged oolite rocks. It is probable that not a single one of these fossils will 

 escape the notice of man, for few rocks are being more extensively utilised. 

 The upper layers are being carried away to be converted into lime, whilst the 

 lower beds supply a highly valued building stone, which has been largely used 

 for some of the monumental edifices of London. In recent times most of the stone 

 quarried on the " island " has been employed in the construction of a breakwater 

 planned towards the close of the last century, but only commenced in 1847, mainly 

 with the view of opposing to the French Cherbourg an English Cherbourg of even 

 greater strength. This prodigious breakwater is the largest work of the kind ever 

 undertaken, for nearly 6,000,000 tons of stone have been sunk in the sea to protect 

 against winds and waves an artificial harbour having an area of 2,107 acres, where 

 the largest men-of-war find secure riding-ground. The first portion of the break- 

 water runs from the shore due east for about 1,800 feet, and serves the inha- 

 bitants of the island as a promenade. Then comes an opening of 400 feet, beyond 

 which the main section stretches 6,000 feet in length, terminating in an ironclad 

 fort armed with the heaviest guns. The summit of Yerne Hill (495 feet) is crowned 

 bv impregnable fortifications, armed with one hundred and fifty cannon, and this 

 citadel, supported by numerous batteries, by a fort on Nothe Hill, near Weymouth, 

 and by two ironclad forts on the breakwater itself, amply provides for the security 

 of the harbour. Breakwaters and forts alike have been constructed by convicts, and 

 this colossal work of modern England, like similar undertakings of ancient Egypt 

 and Rome, has thus been accomplished by the hands of slaves.f 



Put though man may modify the aspects of nature by converting an open 

 bay into a secure harbour, what are his feeble efforts of a day in comparison with 

 the slow, but incessant erosive action of a single geological period ? Beyond the 

 island of Portland and the oolitic rocks of the littoral region, the cretaceous 

 formation extends uninterruptedly as far as Salisbury Plain. That "plain" 



* Lyell, " Principles of Geology." Prcstwich, at the Institution of Civil Engineers, February 2iid, 

 1875. Kinahan, Quarterly Journal of the G eolotjieal Society, February Ist, 1877. 



t The work occupied about a thousand convicts between 1847 and 1872, and cost £1,043,000. 



