B.C.) to Pomponius Nida, to Strabo (xvii. 1), who traces it through Aristotle up to Homer's "heaven-descended stream" and to Pliny (v. 10). For the same reason the reverse is the case with the two southern arteries; their high water, with certain limitations in the case of the Congo, is in our winter. By the condition of their courses, all the four magnates are broken into cataracts and rapids at the gates where they burst through the lateral chains; the Mosi-wa-túnya (smoke that thunders) of the Zambeze, and the Ripon Falls discovered by Captains Speke and Grant upon the higher Nile, are the latest acquisitions to geography, whilst the "Mai waterfall," reported to break the Upper Congo, still awaits exploration. This accident of form suggests a division of navigation on the maritime section and on the plateau-bed which, in due time, will be connected, like the St. Lawrence, by canals and railways. All but the Nzadi, and perhaps even this, have deltas, where the divided stream, deficient in water-shed, finds its sluggish way to the sea. The largest delta at present known is the Nigerian, whose base measures 155 direct geographical miles between the Rivers Kontoro east, and Benin west. Pliny (v. 9) makes the Nile delta extend 170 Roman miles, from the Canopic or African to the Pelusiac or Asiatic mouth, respectively distant from the apex 146 and 166 miles; the modern feature has been reduced to 80 miles from east to west, and a maximum of 90 from north to south. The Zambeze extends 58 miles between the Kilimani or northern and the west Luabo, Cuama or southern outlet-at least, if these mouths are not to be detached. The Nzadi is the smallest, measuring a maximum of only 12 to 15 miles from the Malela or Bananal Creek to the mangrove ditches of the southern shore.