The geographical conditions here resemble those of Muckslush Heath in Colman's play, and although Iram Drove is paradise compared with what we have already come through, taken on its own merits it is not an ideal thoroughfare. One mile of it, past Long Swath Barn, brings us to the beginning of Aldreth Causeway, here a green lane, very bumpy and full of rises and hollows. Maps and guide-books vaguely mention Belsar's Hill near this point, and imaginative guides who have not explored these wilds talk in airy fashion of it "overlooking" the Causeway. As a matter of fact, the Causeway is driven squarely through it, and it is so little of a hill, and so incapable of overlooking anything, that you pass it and are none the wiser. The fact of the Causeway being thus driven through the hill and the ancient earthworks that ring around six acres of it, proves sufficiently that this fortress is much more ancient than William the Conqueror's time. It is, indeed, prehistoric. Who was Belsar? History does not tell us; but lack of certain knowledge has not forbidden guesswork, more or less wild, and there have been those who have found the name to be a corruption of Belisarius. We are not told, however, what that general--that unfortunate warrior whom tradition represents as begging in his old age an obolus in the streets of Constantinople--was doing here. But the real "Belsar" may perhaps have been that "Belasius, Præses Militum versus Elye," mentioned in the "Tabula Eliensis," one of William's captains in this long business, from whom descended the Belasyse family. [Illustration: ALDRETH CAUSEWAY AND THE ISLE OF ELY.] Two miles of green lane, solitary as though foot of man had not passed by for years, lead down to the Ouse. Fens spread out on either hand--Mow Fen, Willingham Fen, Smythy Fen, Great North Fen--fens everywhere. It is true they are now chiefly cultivated fields, remarkable for their fertility, but they are saved from being drowned only by the dykes and lodes cut and dug everywhere and drained by the steam pumping-station whose chimney-shaft, with its trail of smoke, is seen far off across the levels. In front rises the high ground of the Isle of Ely, a mile or more away across the river: high ground for Cambridgeshire, but likely, in any other part of England, to be called a low ridge. Here it is noticeable enough of itself, and made still more so by a windmill and a row of tall slender trees on the skyline. A new bridge now building across the Ouse at this point is likely to bring Aldreth Causeway into use and repair again. On the other shore, at High Bridge Farm, the Causeway loses its grassy character, becoming a rutted and muddy road, inconceivably rugged, and so continuing until it ends at the foot of the rising ground of Aldreth. Drains and their protecting banks lie to the left of it; the banks used by the infrequent pedestrians in preference to the Causeway, low-lying and often flooded. [Illustration: ALDRETH CAUSEWAY.] XXXIII