220. REPORT—1857. 
Report of the Proceedings of the Belfast Dredging Committee. 
By Grorce C. HynpMan. 
In the comprehensive Report of the late Wm. Thompson, Esq., made in 1843, 
the Mollusca of Belfast Bay were so far elucidated that but few species have 
since been added, and it may be considered that little now remains to be 
done in that department but to generalize the results, which may be summed 
up at present by stating the numbers to be, of 
Bivalves, Acephala lamellibranchiata, 96 species. 
Brachiopods, Acephala palliobranchiata, 2 species. 
Univalves, | Gasteropoda prosobranchiata, 96 species. 
Univalves, | Gasteropoda opisthobranchiata, 11 species. 
In all 205 species. 
Of the Tunicata, the Nudibranchs, and the Cephalopods, little or no further 
observations have been made since Mr. Thompson’s report. 
The Bay of Belfast is a wide open estuary, without any minor inlets and 
not diversified with any islands, except the Copelands, which lie at its 
entrance on the southern side. It is about seven miles wide between the 
extreme headlands, and within that space its depth does not exceed 10 
fathoms. It is only beyond this line that the depth increases to 20 fathoms, 
and does not reach 50 fathoms till beyond the outermost of the Copeland 
Islands. 
The only river of any magnitude deserving notice that flows into the Bay, 
is the Lagan, which enters at the extreme southern point, and has iu the course 
of ages considerably changed that portion of the Bay, by the deposits of gravel, 
sand, and mud carried down. A very large area over which the tide once 
flowed has thus been gradually filled up; on it now stands a great portion of 
the town of Belfast, with its numerous manufactories, places of business, and 
the abodes of its stirring population. Evidence of this change occurs wherever 
excavations have been made for wells and foundations of buildings, sea sand 
and shells being generally found, sometimes at the depth of 30 feet and more 
in places further up the valley than where the town stands. Further down 
on either side of the Bay extensive changes have also taken place, by the 
gradual rising of mud banks covered with Zostera, where so lately as sixty 
or seventy years ago, people were in the habit of travelling along the strand at 
low water between Belfast and the villages of Holywood and White Abbey. 
Whilst these changes had been going on at the upper end of the Bay, 
alterations of an opposite character were taking place on both sides still 
further down, where, as at Cultra and Ballyhome Bay on the Down side, and 
near Carrickfergus on the Antrim side, large portions of the land have been 
undermined and swept away. Without supposing any variation in the winds 
and tides, these latter changes may in part be accounted for by the continued 
drawing away of gravel and sand, and the removal of numerous detached 
rocks and reefs for building and other purposes, by which the shores have 
been more exposed to the action of the waves than formerly. 
These changes in the bed of the sea must have had a corresponding influ- 
ence upon the Mollusca, many species which inhabited the sandy and muddy 
tracts of shore having been covered up and killed; and several species have 
probably thus become extinct, as they are no longer found living: but on 
this point as yet there is only negative evidence, and the subject requires 
further investigation. 
