772 GEOLOGY. 



cially the pines, bore marks of having been burnt ; others of having been chopped and 

 split, with large wooden wedges in them, and broken axe-heads, somewhat like sacrificing- 

 axes in shape, and this under circumstances and at depths excluding all supposition that 

 the site had been touched from the destruction of the forest to the time of the drainage. 

 Near a large root in the parish of Hatfield several coins of the Roman emperors were dis 

 covered, much corroded and defaced by time ; and, in other places, coins of Vespasian, 

 axes, and links of chains. Hazel nuts, acorns, and bushels of fir-cones were commonly 

 met with. Some of the trees were very large. An oak was four yards across at the 

 base, three and a half yards in the middle, and two yards across the top, which was broken 

 off, the length of the trunk remaining being forty yards. A fir tree also was thirty-six 

 yards long, and estimated to be deficient at least fifteen yards, making in the whole fifty- 

 one yards or 153 feet. Mr. Phillips states, that the highest tree of this kind that ever 

 fell under his notice, was a spruce fir growing near Fountain's Abbey, calculated to be 

 118 feet above the grass. Mr. Pryme concludes upon Hatfield Chase being the site of an 

 ancient forest which the Romans destroyed, partly with the axe and partly by fire, 

 during the prevalence of a south-west wind, the strongest that blows in our island ; and 

 hence the general direction of the larger trees being towards the north-east. De Luc 

 remarks upon the aboriginal forests of Germany and Gaul, that they were largely destroyed 

 by the Romans, in the same manner, and for a similar purpose, to those of Hercynia, 

 Semana, and Ardennes, the remains of which would no doubt be found in equal abundance 

 upon a removal of the soil that has since accumulated on their sites. 



2. Marine shore silt ; sand drift ; submarine deposits ; submarine forests ; raised 

 beaches. 



The agency of the ocean in producing geological changes, wearing away the land by its 

 waves, tides, and currents, and conveying the detritus along with that received from the 

 rivers to new sites ; the consequent washing up of silt along the existing shores from 

 which new land is occasionally gained, with the drifts of the sand inland encroaching upon 

 fertile territories when exposed to the action of winds prevailing in that direction ; these 

 are incidents of physical geography which have been treated of in their place; and, 

 though concealed from observation, it is plain that along the bed of the sea itself form 

 ations must be in constant process, which, if elevated into dry land, would be analogous 

 to the systems of strata which compose our continents. Our knowledge of the bottom of 

 the sea, with little exception, depends upon the simple apparatus of the mariner a line 

 and plummet to ascertain the depth of water, with the addition of a little grease 

 attached to the lower extremity of the plummet, to which particles adhere when it strikes 

 against the bottom, from which we learn the quality of the soil. From a vast number 

 of observations of the bed of the German Ocean, notoriously encumbered with sand 

 banks or great accumulations of debris, Mr. Stevenson calculated their aggregate super 

 ficial extent to amount to no less than 27,443 square miles, or an area equal to about 

 5 of the whole surface of that sea. To render these dimensions more familiar by 

 comparison, it may be stated that Great Britain contains about 77,224 square miles, so 

 that the area of the sand-banks bear a proportion equal to about one third of the whole 

 terra firma of England and Scotland. Taking an average of the height of the banks, 

 and the depth around each respectively, with their superficial area, the aggregate cubical 

 contents of the whole of these immense collections of debris was estimated at no less 

 than 2,241,248,568,110 of cubic yards, equal to twenty-eight feet of the firm ground 

 of Great Britain in perpendicular height or depth, supposing the surface to be a level 

 plane. 



Submarine forests, traceable at low water, have been observed at various points along 

 the coasts of the United States and France, those of Great Britain with its adjacent 



