616 W I S W I S llth century it was given by Oswy and Leoflecle to the convent of Ely, on the admission of their son Alwyn into that monastery. After the subjugation of the Isle of Ely William erected a strong castle at Wisbech to hold the district in subjection. At Domesday the manor was held by the abbot of Ely, and possessed extensive fisheries, especially of eels. In 1190 Richard I. granted to the tenants of the manor exemption from tolls at all fairs and markets in England, a privilege confirmed by King John, who in 1216 visited the town. In 1236 the town and a great part of the castle was destroyed by an inundation, and the castle lay in ruins till the 15th century, when Morton, bishop of Ely, erected a new building of brick for an episcopal residence. In the reign of Elizabeth it was appropriated to the confinement of state prisoners, among others of Robert Catesby. During the Protectorate it was purchased by Thurloe, afterwards secretary of state, who in 1660 erected an en tirely new one from designs of Inigo Jones, when some Roman bricks were discovered. On the Restoration it again came into the possession of the bishops of Ely, who sold it in 1793, and all remains of it have now disappeared. Anciently the town possessed eight guilds in addition to that of the Holy Trinity, to which they were subordinate. This guild received royal sanction from Richard II. in 1393, and held its last meeting in 1557. The town received a charter of incorporation from Edward VI. in 1549, which was re newed by James I. in 1611, and confirmed by Charles II. in 1669, remaining in force till the passing of the Municipal Act. See Watson s Historical Account of Wisbech, 1827; History of irisbech, 1833; and "Wisbech Castle," in Journal of Brit. Arch. Assoc., 1879. "VVISBY, a picturesque old town on the west coast of the Swedish island of Gotland. It has a considerable trade, but does not occupy half the space enclosed within its old walls, which, with their towers, still survive. These walls, which were built partly on the site of older struc tures, date from the thirteenth century. The vacant spaces of the town are used as gardens, in some of which are fine ruined churches. The church of St Mary (built 1190- 1225) is used as the cathedral. Of the ten ruined churches the most interesting is that of St Nicholas, partly in the Romanesque partly in the Gothic style. In 1880 the population of the town was 6924. In the Middle Ages "Wisby was a port of the Hanseatic League, and a great centre of trade. Its wealth was so celebrated that in an old ballad the people were said to play with the choicest jewels, and the women to spin with golden distaffs. All the principal nations of Europe had representatives at Wisby, and some of its beautiful churches were built by foreign residents. In 1361 it was attacked and plundered by King Waldemar III. (Atterdag) of Denmark. It never recovered from this blow, and when, in 1645, Gotland was finally united to Sweden by the treaty of Bromsebro Wisby had altogether lost its importance. Plate XV. WISCONSIN, one of the North-Eastern Central States of the American Union, has the parallel of 42 30 N. lat. for its southern limit, Lake Michigan for its border on the E., Lake Superior on the N., and the Mississippi on theW. Michigan on the E., Minnesota and Iowa on the W., and Illinois on the S. are its neighbour States. Its area, exclusive of water surface, is estimated at 54,450 square miles. Its length from north to south is 300 miles, its breadth 250 miles ; its lake shore-line exceeds 500 miles. Its surface contours are gentle and pleasing. The lower parts of the State lie about 600 feet above the sea, the highest summits about 1800 feet. Few peaks rise more than 400 feet above their bases, and abrupt elevations of more than 200 or 300 feet are not common except along the Mississippi. The State is merely a swell of land between three notable depressions, the basins of Lake Michigan, Lake Superior, and the Mississippi. The summit of the swell lies within 30 miles of Lake Superior, whence there is a rapid descent northward, with gentler declines to the south-east and south-west, separated by a low swell extending from the summit southward into Illinois. This is traversed in the south-central portion of the State by a remarkable diagonal valley, occupied by Green Bay and the Fox and Wisconsin rivers, cutting it down to within about 200 feet of the lake levels. The easterly slope is traversed longitudinally by a ridge of Niagara limestone, running nearly parallel to the shore of Lake Michigan, at an average distance of about 30 miles. The greatest topographical interest and it is very con siderable lies in the minor surface features. The ice of the Glacial period invaded in force the eastern and northern parts of the State, while an area of 10,000 square miles in the south-western portion was left untouched. Flowing but very irregular contours, accented by morainic peaks and ridges, by gravel knolls, and by domes of drift, mark the former area ; while deep dendritic valleys, erosion cliffs, and castellated outliers give more striking relief to the latter. About 2000 minor lakes dot the eastern and northern portions, all lying within the glaciated area, and caused by the irregular heaping of the drift, or by the erosion of the glaciers. Numerous waterfalls occur in this portion, likewise due to the disturbance of the river- courses by the ice incursion. None occur in the un- glaciated area. Geology. The geological structure of the State is unusually sym metrical (see general geological map in Plate XV. ). It has for its nucleus a great mass of the most ancient crystalline rocks (Archrean). This nucleus occupies the north-central portion of the State, and about it are wrapped successive layers of later-formed rocks, lying concentrically upon each other, and occupying all the rest of* the State. The ancient nucleus consists of granites, gneisses, syenites, and various highly crystalline schists. These are warped, contorted, and twisted among themselves in the most intricate fashion, and, since their original upheaval, have been extensively cut away, exhibiting what was formerly the interior of a much distorted mass. Whether this was originally sedimentary or igneous is undetermined, so great are the vicissitudes it has suffered since its original forma tion. It is extensively traversed by dykes and veins. As yet it has not proved to be productive in minerals of notable commercial value, but affords a wealth of the finest of building material. This forma tion is confidently referred to the Laurentian age, and ranks among the earliest known formations. Around the borders of this nucleus, though not skirting it continuously at the surface, are tracts of Huronian rocks. For the greater part these lie in highly inclined beds, and exhibit evidence of much disturbance since their original formation. Where they come in contact with the Laurentian nucleus, they show, by their unconformity to it, and the erosion of the strata at the contact, that a vast but unknown interval of time separated the two formations. The Huronian rocks are chiefly quartzites, with which are associated quartz-porphyries and various slates and schists, together with layers of igneous rock, either formed at the same time with other members of the series, or subsequently intruded. They embrace also, especially in the north eastern and northern portions of the State, and extending into the upper peninsula of Michigan, valuable beds of iron-ore, as well as beds of carbonaceous material. The amount of carbon contained is large, but unfortunately impure and in the graphitic condition. Limestone also occurs, among the most ancient of its kind. The quartzites of Barren county embrace deposits of pipestone, which also occurs in the Baraboo quartzite, but less notably. Several isolated knobs of quartz-porphyry in central Wisconsin are referred to this formation, and are being extensively utilized for building material, paving, and macadamizing. Apart from the igneous beds, the members of this series were originally sediments, and even now show clearly their fragmental origin. The thickness of the Huronian beds reaches at least 13,000 feet. Overlying the Huronian rocks in the north-western part of the State is an im mense series of igneous beds, sandwiched between which, and also overlying which, are layers of sandstone, shale, and conglomerate, the whole constituting the great copper-bearing (Keweenaw) forma tion of Lake Superior. This crosses the entire north-western corner of the State. The strata are bowed downwards, forming a great trough, the axis of which stretches from near the mouth of the Montreal river to the St Croix. The igneous beds were formed by great outwellings of molten matter, which spread widely over the surface, following each other at longer or shorter intervals, as shown by the presence or absence of intervening deposits or by erosion. The copper of the formation appears to have been brought up by these igneous ejections, and to have been subsequently con centrated by percolating water in the vesicular portions of the old lavas, or in the intervening sandstones or conglomerates, or in fissures traversing the beds, all these forms being present. The formation in Wisconsin has not yet proved sufficiently rich to pay the expense of mining. The thickness of this formation is truly stupendous, estimates ranging from 25,000 to 45,000 feet. The preceding formations are found tilted at various angles ; those which follow lie nearly flat. The Potsdam sandstone, next in order, rests upon all of these at points, coining in contact with different ones in different places. The wear which they had suffered before it was placed upon them indicates a long interval of time.
The thickness of the Potsdam is very irregular, owing to the un-