The charm of these lines of rolling upland is much enhanced by the great rough plain which they inclose--"the Weald" (i.e. Forest), as it is termed--extending in an irregular triangle from the point where the Downs diverge to the British Channel. Geologists have framed many theories as to the formation of the Weald. It belongs to the Oolite formation below the chalk; it is the uppermost member of that formation, and was a deposit of sands and clays in a tropical climate, as is abundantly evident from animal and vegetable remains found there. These prove the existence of islands, banks and forests, forming the shores of a vast estuary, the embouchure of some great river from the west. At one time, the deep chalk deposit extended all over it; but this was disturbed by a line of elevation running along its east and west axis, the superincumbent chalk being broken up and washed away; hence the cliff-like aspect of the Downs in many places, where they descend precipitously to the sandy and gravelly edge of the valley, as to a beach. The remains of the huge land lizards and iguanodons of the Weald, collected by the late Dr. Mantell, form one of the most conspicuous exhibitions of fossil bones in the British Museum. The pretty little fossil ferns, Lonchopteris and Sphenopteris, found nature-printed on the sandstones, are, on the other hand, the very counterparts, in size and delicacy, of their present successors. In early times, as every local historian tells, the Weald was a chief seat of the iron manufacture in Great Britain. The ironstone found here was certainly wrought by the Romans and Saxons, if not by the ancient Britons; and down to the seventeenth century the trade was prosperous. Many an old manor-house, to the present day, attests this former prosperity, while its memories linger also in such local names as Furnace Place, Cinder Hill, and Hammer Ponds. The balustrades round St. Paul's Cathedral are a relic of the Sussex ironworks. Want of fuel, and the more abundant and rich ironstone of the Coal-measures, caused the decay of the industry, after whole forests had been destroyed to feed the furnaces. The old-fashioned cottages, here and there remaining, speak of days of former prosperity among the working-classes; nor are they even yet devoid of comfort, although the transition has been great--ironworkers then, chicken-fatteners now!