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394 Farming of Dorsetshire. 
habits existing crocodiles," and reaching to a length of 18 or 20 
feet ; the Dapedius and other fine specimens •f fish, with which 
the lias abounds ; the Briareus Pentacrites, an animal allied to 
the existing order of star-fish, the numbers of bones in the fingers 
and tentacula of which amount, according to Dr. Buckland's 
calculations, to 100,000, presenting, with the addition of 50,000 
for the ossicula of the side arms, 150,000 bones, with 300,000 
fascicula of fibres, equivalent to muscles ; the Pterodactylus, a 
flying reptile — bird, bat, and lizard ; and, lastly, those great and 
terrible monsters of the lias, the Ichthyosaurus and Plesiosaurus, 
the disjointed bones of which alone suffice to " confound the 
ignorant, and amaze, indeed, the very faculties of eyes" and 
thought ! 
A peculiarly interesting geological district (for a description 
of which my best thanks are due to John Mansel, Esq.) is the 
so-called " Isle " of Purbeck. It is, strictly speaking, a peninsula, 
being bounded on the north by the river Frome and Poole 
Harbour, on the east and south by the Channel, and on the west 
by two rivulets — Luckford Lake, which runs into the Frome, 
near East Stoke, and Airish mill-stream, which empties itself 
into the sea at Worborrow Bay. Between the sources of these 
streams, a distance of half a mile, the "island" is joined to the 
rest of tlie county. It comprises an inconceivable variety of 
soil, occasioned by the rapitl change of strata in this narrow 
district. The black shales of the Kimmeridge clay, which forms 
a part of the coast line, give a sombre appearance to tlie cliffs, 
which rise above the sea to a height of fiom 100 to 250 feet. 
Near Corfe Castle and Creech are beds of pipeclay, charac- 
teristic of the Bagshots. This clay is a source of great profit, 
and affords employment to a large number of workmen in the 
neighbourhood. It is conveyed to the Frome by means of a 
tram-road, and from thence, by ship, into Staffordshire. The 
following section of one of these clay pits is given in the Rev. 
John Austin's monograph upon the geology of Purbeck : — 
Bed of lignite 10 
Grey clay with carbonized leaves 2 
Yellow sandy clay with leaves 2 
Ferruginous sand a few inches. 
White sand 30 
Pipeclay 11 to 14 
The leaves whose delicate impressions are preserved in the 
clay belong mostly to the natural order Silicidse. Remains of 
liymenopterous and coleopterous insects are also found in these 
beds. In the Purbeck series arc discriminated no fewer than 130 
beds, varying considerably in character, the fossils evidencing 
changes from fresh to sea-water, and from sea-water to fresh, 
