Lankester— Crag. 103 
When the well was bored, the tool, after passing through a layer of 
flints, sunk suddenly, and the water rushed up with a force that (as 
the late Superintendent expressed it to me) shook the hill. This 
shows that the spring is connected with an extensive and free reser- 
voir. There are two other wells, at distances of a mile and amile and 
a half, in a straight line east of this one, which are evidently connected 
with the same reservoir ; for on Mondays, when the pumps are not 
at work at the Water-works, the water stands higher than usual in 
those wells. I conceive, then, that the motion of the water in this 
subterranean reservoir, caused by the draught of water at these 
wells, disturbed the equilibrium of the roofing of the chasm at a 
point where it was barely stable, and caused the subsidence in 
question. 
This is rendered the more probable because it is evident that this 
natural pit is on a line of subterranean drainage, as is shown by the 
hole being dry at a level lower than that of the river. The water in 
the Colchester well stands at about 10 feet below the level of the 
river; which being more than a mile lower down the stream, would 
give at Lexden a greater difference between the subterranean and 
surface-drainage levels. 
Til.—On toe Cracs or Surrotk anp ANTWerpP. (Parr I.) 
By E. Ray Lanxsster, Esq. 
ee Suffolk Crags. — There are few deposits in this country 
which form so admirable a field for study as the Crags* of Suf- 
folk. Unique as to age, the sole representatives in England of the 
great Pliocene deposits of Europe, it becomes a matter of very high 
interest to identify them in any way with particular strata in other 
countries. The lowest of these Crags occurs in small patches over 
an area of about eighty square miles, and consists of either loose or 
compact light-coloured sand, alternating with bands of Polyzoa, which 
sometimes form a kind of limestone. From this Crag 299 species 
of Mollusca have been obtained: of these, 148 are extinct, 151 are 
* The most important notices and memoirs that have been written on the Crags 
of Suffolk and Essex are—by Mr. Charlesworth, Proceed. Geol. Soe. 1835, vol. 11. 
p- 195; Phil. Mag. 1835, 3rd Ser., vol. vii. pp. 81, 465; Report Brit. Assoc. 1836, 
Trans. Sect. p. 84; by Sir C. Lyell, in his ‘ Principles’ and ‘ Elements of Geology,’ 
and in the Mag. Nat. Hist. 1839, New Ser., vol. 11. p. 313; Mr. Prestwich, Quart. 
Journ. Geol. Soe. 1849, vol. v. p. 350; Mr. S. V. Wood’s Monograph of the Shells 
of the Crag (2 vols. 1848-56 ; Palzontographical Society), and his paper on the 
Extraneous Fossils of the Red Crag, Quart. Journ. Geol. Soc. 1858, vol. xv. p. 32; 
and Mr. 8. V. Wood, jun., on the Red Crag, Annals Nat. Hist. 1864, 3rd Ser., vol. 
xiii. Besides the Mollusca, the Cirripedia, Echinodermata, Polyzoa, Corals, and 
Entomostraca of the Suffolk Crag have been figured and described in the Mono- 
graphs of the Paleontographical Society. The Crags of Antwerp were treated of 
by Sir C. Lyell in the Quart. Journ. Geol. Soc. 1852, vol. viii. p. 281, &e.; and 
several papers on these deposits and their fossils are to be found in the publications 
of the Brussels Academy, &c. Reuss has described the Foraminifera of the 
Antwerp Crag in the Proceed. Vienna Acad., vol. xlii., 1860, p. 355, &e, 
