78 



ALMOND. 



ception, and adequate to any purpose which we can 

 conceive it designed to serve. 



We may now, however, proceed from the mightier 

 phenomena which occupy the attention of the geolo- 

 gist, and which have tended to produce such extra- 

 ordinary changes on the surface of our globe, to the 

 lesser though no less certain effects resulting from 

 the action of rivers in comparatively modern times. 



The wearing and transporting powers of a running 

 stream depend upon the volume of water, and the 

 quantity and size of the solid matter suspended, and 

 the velocity with which it moves. A river generally 

 runs with the greatest rapidity in the higher parts of 

 its course, where, indeed, it often consists of a suc- 

 cession of torrents and cataracts for many miles, but 

 it has not yet acquired its full destructive force, 

 because the mass of water is still comparatively small, 

 nor has it yet become loaded with solid matter. In 

 the lower part of its course, long before it joins the 

 sea, it has usually reached a level country, and there 

 its velocity becomes greatly retarded. The Senegal 

 in Africa does not, according to Adanson, fall more 

 than two feet and a half from Pod or to the sea, a 

 distance of sixty leagues. But the increase of the 

 volume of water in rivers during the flood seasons is 

 often prodigious. The bed of the Mississippi, at 

 Natchez, about 300 miles above New Orleans, mea- 

 suring along the course of the river, scarcely exceeds 

 a mile in breadth when the water is low, whereas in 

 the flood season the mass of waters is nearly thirty 

 miles wide. The Orinoco, at St. Thomas's, two 

 hundred miles from its embouchure, is about three 

 miles and a half wide in the dry season ; but when 

 flooded, its waters, according to Dupens, stretch out 

 to the enormous breadth of seventy miles. 



Here we find a beautiful provision for 4 fertilising 

 the surface of the earth, which is well worth our ex- 

 amination. Fresh deposits are thus added to the 

 alluvial formation, which are of the greatest value in 

 the processes of vegetation. 



How truly may it be said that where the Nile is 

 there is Egypt, and where the Nile is not there does 

 that in some respects fertile land cease to exist for the 

 benefit of man. The inundation of this river, and the 

 formation of its alluvial deposits, are phenomena 

 which have attracted the greatest attention at every 

 period of scientific inquiry. The ancients, who 

 witnessed no instance of inundation in any other 

 river, exhausted themselves in conjectures as to the 

 cause ; and each found it more easy to overthrow his 

 neighbour's hypothesis, than to establish his own. 

 Even Pococke ascribes it merely to the effect of the 

 Etesian winds blowing from the north at a certain 

 season. The cause is now perfectly ascertained in the 

 periodical rains which fall from June to September, 

 throughout the northern tropical regions. From 

 these the Nile is exclusively fed, as it scarcely receives 

 a single stream in its course, north of the tropic. The 

 rise begins to be felt about the 17th of June, and 

 continues till August, when the river is at its height, 

 and all the level parts of the country are overflowed. 

 On the level plain of the Delta, inundation takes 

 place spontaneously, and at an early period. When 

 the waters have retired, the soil of Egypt is covered 

 with a slime more or less thick. Its colour is at first 

 black, but in drying it changes into a yellowish 

 brown. It then cracks, and exhibits fissures, showing 

 that the slime was deposited in horizontal layers. 

 This slime is about one-half composed of alumine, 



and contains also a large proportion of carbonate of 

 magnesia. The principles of vegetation are thus 

 copiously contained in it, so that it not only stands 

 itself in no need of manure, but supplies its place to 

 other lands. On the banks of the river it contains a 

 reat quantity of sand, which diminishes in proportion 

 as it is carried to a distance from them. Hence clay 

 is produced in all the various states which the arts 

 require. 



Water, when in rapid motion, produces alluvial 

 deposits, differing very materially in their character 

 from those we have now been describing. The force 

 of a river, when directed against any obstacle in its 

 course, is very considerable, even by its own weight 

 alone, especially if it be flowing over a highly-inclined 

 surface ; but its destructive power is greatly augmented 

 if it be loaded with sand and gravel. In floods, very 

 considerable blocks are carried by the stream to great 

 distances ; for it must be remembered that these are 

 much more easily moved in water than on land. If 

 the water flows with a velocity of three inches per 

 second, its force, when free from suspended matter, is 

 sufficient to tear up fine clay ; six inches per second, 

 fine sand ; twelve inches per second, fine gravel ; and 

 three feet per second will tear up beds of loose stones 

 of the size of an egg. The flood occasioned by the 

 bursting of the barrier of a lake in the valley of 

 Rpgnes, near Martigny, in the Vallois, moved at first 

 with the tremendous velocity of thirty-three feet per 

 second, it was afterwards diminished to eighteen and 

 eleven, and at the end of its course, when the water 

 reached the Lake of Gfeneva, it was still running at the 

 rate of six feet per second. From the barrier to this 

 point, the fall is 4187 Paris feet, the distance is forty- 

 five miles, and the mass of water passed over this space 

 in five hours and ahalf. It swept along houses, bridges, 

 and trees ; masses of rock, equal in dimensions to 

 houses, which it tore out of an ancient alluvial soil, 

 were carried a quarter of a mile down the valley. 

 A flood that happened in the north of Scotland, in 

 1829, afforded numerous examples of the power <>(' 

 running water to transport large blocks of stone. On 

 the river Nairn, a fragment of sandstone rock, four- 

 teen feet long by three wide, and one foot thick, wns 

 carried above two hundred yards down the river. 

 The river Don forced a mass of four or five hundred 

 tons of stones, many of them two or three hundred 

 pounds weight, up an inclined plane, rising six feet in 

 a few yards, and left them in a rectangular heap. 

 about three feet deep, on a flat ground. If then sued 

 large masses can be moved by the action of water, 

 even by the ordinary and evory-day operations of 

 nature, we may easily understand how, in the gradual 

 progress of ages, the whole amount of alluvial soil 

 which we now find may have been brought into its 

 present situation. 



Under the article GEOLOGY will be given a general 

 view of the connection which alluvial soils hear to the 

 various stratified masses which form our globe, when 

 it will be shown how admirably they are proportioned 

 to the wants and comforts of man, as well as to the 

 subordinate parts of the animal kingdom. 



ALMOND. The well known' fruit of the Ami/g 

 da/us communis. There are six species; two of Ihem 

 are dwarf ornamental shrubs, the rest are small trees, 

 bearing fruit of different qualities, that from the cmn- 

 munis and its varieties being most esteemed. The 

 shores of both sides of the Mediterranean Sea are 

 the native habitat of these fruit trees, and whence 



