136 BURIED FOREST IN NORFOLK. [Ch. XL 



rials heaped upon the embankment. In 1852 I saw a remarkable in- 

 stance of such a downward and lateral pressure, in the suburbs of Boston 

 (IT. S.), near the South Cove. With a view of converting part of an es- 

 tuary overflowed at high tide into dry land, they had thrown into it a 

 vast load of stones and sand, upwards of 900,000 cubic yards in volume. 

 Under this weight the mud had sunk down many yards vertically. Mean- 

 while the adjoining bottom of the estuary, supporting a dense growth of 

 salt-water plants, only visible at low tide, had been pushed gradually up- 

 ward, in the course of many months, so as to project five or six feet above 

 high-water mark. The upraised mass was bent into five or six anticlinal 

 folds, and below the upper layer of turf, consisting of salt-marsh plants, 

 mud was seen above the level of high tide, full of sea shells, such as Mya 

 armaria, Modiola plicatula, Sanguinolaria fusca, JVassa obsoleta, Natica 

 triseriata, and others. In some of these curved beds the layers of shells 

 were quite vertical. The upraised area was 75 feet wide, and several hun- 

 dred yards long. Were an equal load, melted out of icebergs or coast-ice 

 thrown down on the floor of a sea, consisting of soft mud and sand, similai 

 disturbances and contortions might result in some adjacent pliant strata, 

 yet the underlying more solid rocks might remain undisturbed, and newer 

 formations, perfectly horizontal, might be afterwards superimposed. 



A buried forest has been adverted to as underlying the drift on the 

 coast of Norfolk. At the time when the trees grew, there must have been 

 dry land over a large area, which was afterwards submerged, so as to 

 allow a mass of stratified and unstratified drift, 200 feet and more in 

 thickness, to be superimposed. The undermining of the cliffs by the sea 

 in modern times has enabled us to demonstrate, beyond all doubt, the 

 fact of this superposition, and that the forest was not formed along the 

 present coast-line. Its situation implies a subsidence of several hundred 

 feet since the commencement of the drift period, after which there must 

 have been an upheaval of the same ground ; for the forest bed of Nor- 

 folk is now again so high as to be exposed to view at many points at low 

 water ; and this same upward movement may explain why the till, 

 which is conceived to have been of submarine origin, is now met with 

 far inland, and on the summit of hills. 



The boulder formation of the west of England, observed in Lanca- 

 shire, Cheshire, Shropshire, Staffordshire, and Worcestershire, contains 

 in some places marine shells of recent species, rising to various heights, 

 from 100 to 350 feet above the sea. The erratics have come partly from 

 the mountains of Cumberland, and partly from those of Scotland. 



But it is on the mountains of North Wales that the " Northern drift," 

 with its characteristic marine fossils, reaches its greatest altitude. On 

 Moel Tryfane, near the Menai Straits, Mr. Trimmer met with shells of 

 the species commonly found in the drift at the height of 1392 feet above 

 the level of the sea. 



It is remarkable that in the same neighborhood where there is evi- 

 dence of so great a submergence of the land during part of the glacial 

 period, we have also the most decisive proofs yet discovered in the British 



