I formed the opinion that the white ants have rendered valuable service to Egypt by amassing the fertile mud which is carried down to the Nile Delta, and venture to put forward the following considerations in support of the theory. On entering the Abyssinian borderland, one cannot help remarking the structure of the ground. Our track lay generally along watercourses, and the beds of dry mountain torrents. Here the soil was composed of sand, shingle, and pebbles. On either bank, and for some distance beyond, lay an expanse of basaltic stone, on which little earth was to be seen. Grass grew there, but by no means so abundantly as in the plains, and there were climbing plants, such as convolvulus, and ivy, which clung to nearly every tree. These creepers made the path extremely difficult to follow. Further away from the watercourses lesser vegetation and longer grass appeared. The white ants’ nests, from nine to twelve feet in height, were found here, usually close to a soft wooded tree. The roots of it, in most cases, had been attacked by the insects, and converted into “white ant earth.” The trunk afterwards undergoes the same process, and by the advent of the rainy season only the outlying twigs remain intact. A heavy gust of wind will then overthrow the _simulacrum_ of a tree. The rain falls in torrents, and the compost which the insects have made of the timber is broken up and carried by innumerable channels into the tributaries of the Atbara, and finally reaches the main stream. It is well known that the Atbara brings down the greatest quantity of this mud, the Blue Nile carrying less, and the White Nile, the most sluggish stream of the three, least. The two more rapid rivers rise in Abyssinia, in regions where the white ant is extremely destructive to vegetation. Moreover, the innumerable ant-heaps[31] are made entirely of earth, which crumbles under the rains, and is swept into the watercourses in the season of floods. And in the dry months the ants—besides devouring straw and the bark of living trees[32]—eat into every branch and twig that the past storms have brought to the ground. Carrying earth into their excavations, they hollow the wood, as in the case of the soft standing timber which they attack, and leave just the outer covering intact. I have often stooped to pick up a stick for the cook’s fire, and found that my fingers broke a thin shell of bark, and scattered the contents. Another circumstance which seemed worthy of remark was that we found no deposit of “Nile mud” within the Abyssinian boundary, nor any earth resembling it; so one may conclude that, as soon as the Atbara, when in flood, reaches the level of the Soudan, it spreads a deposit of this fertile soil beside its banks, though the great mass is carried into the Nile. According to this view, the fertility of the alluvial districts of Lower Egypt is in no slight measure due to _detritus_ from Abyssinia, and the white ants