“The emperor _Severus_ is said to have been the first who intersected the fens with causeways. _Dugdale_ has mentioned one, supposed to have been made by him, of twenty-four miles in length, extending from Denver to Peterborough. This was composed of gravel, about three feet in depth and sixty feet broad, and is covered with moor from three to five feet in thickness. This furnishes another proof of the great alterations which the fens have undergone; yet the changes which have taken place may be illustrated still further. “The celebrated _Sir Robert Cotton_, when making a pool, at the edge of Connington Downs, in Huntingdonshire, found the skeleton of a large sea-fish nearly twenty feet long, about six feet below the superfices of the ground, and as much below the general level of the fens. Many of the bones, which from their long continuance in the earth, were incrusted with stone, were preserved, and are reported to be still in the possession of Sir Robert’s descendants. “At Whittlesea, in digging through the moor, for the purpose of making a moat to secure a plantation of fruit trees, at eight feet deep, a perfect soil was found, with swaths of grass lying on it as they were at first mowed.” This seems to indicate that the inundation which overwhelmed the country, happened in summer, or early in autumn, and had not been foreseen by the inhabitants. The _nuts_ and _acorns_ before-mentioned, will also corroborate this conjecture, as to the time of the year when this catastrophe happened; and so do the swaths of grass, or mown hay, as to the suddenness of it. “When the foundation was dug for Shirbeck sluice, near Boston, at the depth of sixteen feet a _smith’s forge_ was discovered embedded in silt, with all the _tools_ belonging to it, several _horse-shoes_ and some other articles. Also in setting down a sluice a little below Magdalene Fall, a stone eight feet long and a cart wheel were found at a similar depth below the surface. Likewise near the river Welland, at the depth of ten feet, several boats were dug up; and at the same depth, on the opposite side of the river, the remains of ancient tan-vats or pits, and a great quantity of horns were found.