450 M A N M A N whence a stairway conducts us clown to the banks of the River Styx, a body of water 40 feet wide and 400 feet long, crossed by a natural bridge. Lake Lethe comes next a broad basin enclosed by walls 90 feet high, below which a narrow path leads to a pontoon at the neck of the lake. A beach of the finest yellow sand extends for 500 yards to Echo river, the largest of all, being from 20 to 200 feet wide, 10 to 40 feet deep, and about three-quarters of a mile lon^. It is crossed by boats. The arched passage-way is very symmetrical, varying in height from 10 to 35 feet, and famous for its musical reverberations, not a distinct echo, but an harmonious prolongation of sound for from 10 to 30 seconds after the original tone is produced. The long vault has a certain keynote of its own, which, when firmly struck, excites harmonics, including tones of incredible depth and sweetness. The fauna of Mammoth Cave has been classified by Putman, Packard, and Cope, who have catalogued twenty-eight species truly subterraneous, besides those that may be regarded as stragglers from the surface. They are distributed thus : Vcrtcbrata, 4 species; Insecta, 11 ; Arachnida, 6 ; Myriapoda, 2 ; Crustacea, 2 ; Vermes, 3. Ehrenberg adds a list of 8 Polygastric Infusoria, 1 fossil infusorian, 5 Phytolitharia, and several microscopic fungi. A bed of Agaricus was found by the writer near the Eiver Styx ; and upon this hint an attempt has been made to propagate edible fungi in this locality. The most interesting inhabitants of Mam moth Cave are the blind, M ingless grasshoppers, with extremely long antennas ; blind, colourless crayfish (Uambarus pellucidus, Telk.) ; and the blind fish, Amblyopsis spelseus, colourless and viviparous, from 1 inch to 6 inches long. The Cambarus and Amblyopsis have wide distribution, being found in many other caves, and also in deep wells, in Kentucky and Indiana. Fish not blind are occasionally caught, which are apparently identical with species existing in streams outside. The true subterranean fauna may be regarded as chiefly of Pleistocene origin ; yet certain forms are possibly remnants of Tertiary life. The strongly marked divergence of these animals from those found outside convinced the elder Agassiz that they were specially created for the limits within which they dwell. But the opinion now held is that they are modified from allied species existing in the sunlight, and that their peculiarities may all be accounted for on principles of evolu tion, the process being accelerated (or retarded) by their migra tion from the outer world to a realm of absolute silence and perpetual darkness. MAN. See ANTHROPOLOGY (vol. ii. p. 107 sq.) and the articles on the various contributory sciences there referred to. Compare also MAMMALIA, above, p. 444. MAN, ISLE OF, a dominion of the crown of England, situated in the Irish Sea, almost equidistant from England on the east, Scotland on the north, and Ireland on the west. It lies between 54 2 and 54 25 N. lat., and between 4 18 and 4 50 W. long., Douglas on the east coast of the island being distant 58 miles west-north-west from Fleetwood, while Peel on the west coast is 65 miles south-east of Belfast. The greatest length of the island is about 33 miles, and its greatest breadth about 12 miles. The total area is 145,325 acres, or about 227 square miles. A mountain range occupies the larger portion of the island, extending from Maughold Head to the Calf Islet; the highest summits Snaefell (2024 feet), North Barrule (1842), and Slieu Chairw (1808) are in the north-west. These mountains rise abruptly from the narrow tract of almost level ground which forms the extreme northern boundary of the island; and between their lofty chasms are the lovely and picturesque recesses of Ravensdale, Sulby Glen, Glen Aldyn, and Ballure. The fine scenery of the mountains has been made more accessible by the construc tion of a series of roads, commanding at many points views unsurpassed in the United Kingdom for picturesqueness and variety. In the south-western portion of the mountain range only one summit, that of South Barrule (1585 feet), rises above 1500 feet. From Peel southwards along the western shore the mountains stretch to the very edge of the coast-line, and at the south-western extremity the shore i.s wildly precipitous, especially at Cronk-ny-Irree-Lhaa, which rises abruptly from the sea to the height of 1449 feet; at Brada Head, near which Brada Hill forms an almost precipitous wall over 700 feet in height ; at Calf Islet, surrounded by rugged broken rocks ; and at Spanish Head (said to take its name from the destruction which, there overtook a portion of the Spanish Armada). Towards the south-eastern shore the mountains slope more gradually towards the sea, the coast of which is generally low and sandy, being indented by several finely rounded bays, in cluding Castletown Bay and Derby Haven. From Derby Haven to Maughold Point the coast is frequently bold and rocky, and the numerous creeks and bays, the largest of which are Douglas Bay and Laxey Bay, greatly add to the charm and variety of the scenery. From Maughold Head round to Peel the coast presents little of special interest, being formed in great part of sand and gravel cliffs, although along the western side the bold clay-slate forma- mation again appears. Isle of Man. The largest river in the island is the Sulby, which rises near Snaefell, and, after flowing northwards through a rugged glen to Sulby village, winds eastwards through a level and well-cultivated country to the sea at Ramsey. The Neb or Great River, which is formed by the junction near Slieuwhallin of a stream rising near South Barrule and flowing north by the Foxdale Glen, and of another flowing south from Sartfell by Rhenass, passes west to the Irish Sea at Peel. The Silverburn flows southwards from South Barrule to the Castletown Bay. The Dhu and Glass flowing eastwards unite before entering the sea at Douglas, which takes its name from their union. The streams abound with trout, and fishing is generally per mitted without restriction. There are no lakes. Geology. The greater part of the island is formed of slaty Silurian rocks of identical .formation with the mountainous regions of Cumberland and Westmore land. No characteristic fossils, however, exist to deter mine their exact age except one, Palseochorda major, found in the Skiddaw slates. The line of strike is from south-west to north-east, and the strata are highly in clined. The mountains for the most part present a smooth rounded appearance, superinduced by prolonged subaerial wrste. The clay-slate formation is sometimes broken through by intrusions of granite and other eruptive rocks.
The "greenstones" are especially visible at Brada Head.