Mr. Gwyn Jeffreys on Dredging among the Hebrides. 395 
stony, and never of soft ground, besides dead shells of the same 
and similar species. Thatis more than twice the average depth 
supposed by Professor Lovén to be the limit of hard ground. 
The Hebridean sea-bed, at very moderate depths (which Dr. 
Wallich would call “ shallow water’), mainly consists of a soft 
and more or less tenacious mud, mixed with stones of different 
sizes, and resembling in its composition the boulder-clay or gla- 
cial drift of Scotch geologists. It tells us of rocks ground down 
by glaciers year after year in an arctic region—of the mud pro- 
duced by such attrition being carried into the sea in the thawing- 
season by overwhelming floods, “‘non sine montium clamore ” 
(see Dr. Kane’s description of the great Humboldt glacier)—of 
its dispersion over the sea-bed by the action of tides and cur- 
rents—of the deposit thus formed being inhabited by a variety 
of animals of a high northern type during a long and quiet 
course of time—of the sea-bed being elevated by slow degrees 
above the surface of the water by an agency which we cannot satis- 
factorily explain, but which may be volcanic, or perhaps caused 
by steam*—of the consequent extermination of these marine 
animals—of an interval during which the raised sea-bed was 
dry land—of a gradual amelioration of the climate—of another 
oscillation of the earth’s crust in a downward direction, when 
the surface of the land, covered by its former deposit, again be- 
came the bottom of the sea—and of a fresh succession of life, 
which is still in existence. Thus a cycle of similar events con- 
‘tinually recurs. Nothing is lost or altogether perishes; all the 
old materials are used up, and assume new forms. It is the 
fashion to quote Lucretius. I will only indulge in two lines; 
they seem not to be inapplicable to the present subject :-— 
* Hue accedit uti quicque in sua corpora rursum 
dissoluat natura neque ad nilum interemat res.” 
The kind assistance of Mr. Alder, Dr. Carpenter, the Rev. A. 
M. Norman, Messrs. Henry and George Brady, Dr. M‘Intosh, 
and Mr. Peach—all of them experienced zoologists—enables me 
to supplement this Report with notices of other departments of 
the invertebrate fauna, which have resulted from the last grant 
made to me. Several new species, especially among the smaller 
Crustacea, have occurred ; and our knowledge of geographical 
distribution has been not a little advanced by the work. Mr. 
Norman’s services especially deserve acknowledgment. 
I have made my usual contribution to the British Museum. 
* Vide Mr. R. A. Peacock’s pamphlet ‘On Steam as the Motive Power 
in Earthquakes and Volcanoes, and on Cayities in the Earth’s Crust.’ 
Jersey, 1866, 
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