All these defects are, however, cancelled by the unexampled toughness and indestructible nature of the wood; it might fairly be asked from what other material could boats 60 feet long and 20 feet broad be constructed without ribs or braces. The sides of the boat are a foot thick, and are formed of layers of different lengths, which acquire stability and firmness from their own support. An empty boat, seen from inside, has somewhat the appearance of an elongated shell of half a hazel-nut. The planks, where they overlap or are dove-tailed together, are fastened by iron nails driven in perpendicularly, the necessary holes being bored from the outer to the inner surfaces in such a way that the same nail holds together two, or occasionally more, thicknesses of wood. In this manner, with much trouble and more measuring, is obtained the proper curvature of the hull, which, as a whole, is marked by a complete symmetry. The cost of the stout iron nails, and the rapid wear of axe and saw, make the expenses of building these boats so considerable that they amount to five times as much as oak vessels of the same size in Europe. A mast about 20 feet high bears the giant-yard of the single lateen sail, which is generally half as long again as the boat. [Sidenote: NIGHT ON THE RIVER.] Amid the farewell salutations of a large concourse, among which my people counted numerous friends and relations, we pushed off from the shore. Without delay we took our onward course to the mouth of the Blue Nile, doubling the Ras-el-Khartoom, that large promontory, which resembles in form the snout of an animal; it gives its name to the town, and is the partition land between the two arms of the Nile. Bulky and ponderous as was our boat, the power of the north wind laid its hold upon our giant-sail, and carried us with the speed of steam towards the south. On the forenoon of the following day we found ourselves already 1° below the latitude of Khartoom. We sailed, without staying our course, through the night, which was cheered by the moonlight. I was sleepless with excitement at finding myself at last brought irrevocably to the attainment of my cherished hopes. The universal quiet was only broken by the rush of the bilge-water, and now and then by the cry of the water-birds. Shrouded like mummies in their white garments lay the crew, closely packed upon the narrow deck; and altogether there was something spectral in the stillness of the nocturnal voyage.