184 WEST AFEICA. channels merges in the Rio- Grande estuary, less spacious than that of the Geha, although the latter appears to be much the smaller river of the two. The Rio-Grande. The Rio- Grande, called also the Guinala, appears to be the chief waterway in Portuguese Senegambin. It is supposed to rise on the same plateau as the Gambia, flowing not east but west, and under the name of the Ccmba collecting numerous torrents from the Futa- Jallon highlands. Of these the largest is the Tomine, which also gathers its first waters from the neighbourhood of Labe. One of the districts traversed by it is intersected by such a number of rivulets that it takes the name of Donhol, that is, " Land of Waters." Even in the dry season it has a discharge of over 350 cubic feet per second at 90 miles from its source, where it winds through a broad valley skirted on both sides by cliffs from 850 to 1,000 feet high, above which rise the escarpments of the granite rocks, presenting the appearance of superimposed bastions. Lower down the Tomine leaves the region of primitive rocks, trending northwards to the Ccmba through
- blackish sandstone and ferruginous quartz walls furrowed at intervals by the
rocky beds of wild mountain torrents. Below the Tomine-Comba confluence the united stream deserves its Portuguese name of Rio-Grande, for here it is already a " great river," as attested by Goulds- bury and other travellers, who crossed towards the head of the bend it describes from north to west, parallel with the Geba. But in this district a part of its course no less than 90 miles long remains still to be explored, so that it is somewhat doubtful whether the Comba discharges into the Rio-Grande estuary, or flows north- west to the Geba. But as figured on the maps the Rio-Grande would comprise the whole of the Tomine basin, with a total length of about 450 miles. The tides, which ascend 60 miles into the interior, convert the lower reaches into an intricate system of saline channels winding round a number of marshy alluvial islands, which are continued seawards by the Bissagos archipelago. Farther south the seaboard is broken into peninsulas and projecting headlands by several creeks or streams terminating in estuaries, and all flowing parallel to each other from north-east to south-west. Of these the Cassini alone deserves the name of river. Rising 120 miles from the coast in the hilly region west of the Tomine basin, it enters the sea through a funnel-shaped inlet accessible to the largest vessels for 30 miles. The Bissagos Archipelago. The Bissagos Islands, which were formerly attached to the mainland, differ from the other insular formations only in their more seaward position, and in the greater breadth of the intervening channels, which have not yet been thoroughly explored. The group, which is defended seaward by a line of dangerous breakers, comprises about thirty islets of various size, besides innumerable reefs, many of
