Ash), Betula alba (Birch), Quercus Robur (Oak), with other indigenous trees, grow luxuriantly within 15 or 20 yards of high-water-mark. The reason of this appears to be, that they grow upon the lower part of very high land, which causes an eddy to be formed about them when the wind blows from the sea; and by the same high land they are protected from the south and south-west winds. On the top of the rocks the wind rages with the greatest fury, even the grass seeming blighted, whereas below the rocks every plant appears in a thriving state, and some houses sitnated on the lower part never have their thatched roofs disturbed by the storms. In every other part along the coast where land is of the same form it is covered with thriving wood; but where the land is nearly level for a length of way inland no wood appears, and every hedge is seen never to rise higher than the top of the bank which protects it from the wind. Therefore in order to plant near the sea on a low shore, it is necessary to commence the plantations a considerable way inland, and to allow the young trees to have others several feet taller than themselves behind them: these will have the same effect as high land, for by means of the opposition offered by innumerable stems and branches, the force of the wind will be greatly lessened; as we may find by standing on the windward side of a thick wood during a storm, where, if the trees are lofty, the wind is much less violent than on an open plain. In water the effect of this kind of opposition is visible, for if into the bed of a swift stream we drive a number of stakes, the water, although it continues to flow, yet has its velocity diminished considerably. Our first plantations in an exposed place ought always to be of such trees as are natives of mountains, for these are fitted by nature to bear the rude blasts of winter, and by the the stiffness of their leaves, or flexibility of their footstalks, to remain uninjured by a summer storm. Of the first, we have the various race of pines; of the last, the Birch, the Aspen, and the Mountain Ash*. Thus by a careful inspection of the operations of nature, is the hand of man enabled to collect the productions of distant countries around his home, cover the arid heath with waving green, and make the lonely wilderness assume a pleasing gloom. An Account of an Experiment on the Velocity of Water flowing through a Vertical Pipe. From the JOURNALS of the ROYAL INSTITUTION of GREAT BRITAIN. IT has been asserted by some writers on hydraulics, and Venturi describes a particular experiment in support of the assertion, that the discharge of water running out of the bottom of a cistern, through a descending pipe, is nearly the same as if the cistern were continued through the whole height, from the surface of the water to the orifice of the pipe, and the water were then discharged from the bottom of this cistern by a short pipe in any direction. The apparent difficulty of finding a cause adequate to the effect, on the one hand, and the authority of Venturi on the other, made it desirable that the experiment should be repeated; and an apparatus was con * Among the rocks of Agnew's Hill in the County of Antrim, I found the Populus tremula (Aspen Tree) growing luxuriantly on the eastern face, at about the elevation of 1,450 feet. And on the top of Slemish, the Sorbus aucuparia (Mountain Ash) exposed to every storm at the elevation of 1,398 feet. structed, structed, in the house of the Royal Institution, for per forming it in a simple and satisfactory manner. The cistern employed was a cube of nine inches: close to the bottom a cylindrical tube was inserted, in a horizontak direction, nine inches in length, and half an inch in diameter; another tube, of exactly the same dimensions, was provided with a flat funnel at its upper end, and its lower end was fitted to slide in a collar placed in one of the upper angles of the cistern, so that it was supported in a vertical position. Water was poured into the funnel as fast as it could be transmitted through the tube; and, as the surface of the fluid rose in the cistern, the vertical tube was drawn up, so that its lower orifice was barely immersed in the water. It was expected, that if the velocity of the water in the vertical tube were equal to the velocity corresponding to half its length, the water in the cistern would stand at the height of four inches and a half, or one half of that length, and that the pressure of this head of water would generate, in the water flowing through the horizontal tube, nearly the same velocity as the column of water would acquire in its descent through the vertical tube: the friction and resistance being in both cases the same. But the result was far different, and it fully confirmed the truth of the received theory: for the water rose in the cistern to the height of eight inches, which was very nearly the length of the tube. It is true, that the water had already some velocity when it entered the funnel; bat but most of this must have been lost by reflection from its sides and bottom; and the quantity of air bubbles, that were unavoidably carried down with the water, must. have fully compensated the little that remained. The water acquires all its velocity, in consequence of the pressure of the atmosphere acting jointly with its cohesion, in a very small space at the entrance of the tube: consequently, during the whole time of its descent it acquires no new motion, and the whole force of its gravitation must therefore be at liberty to act in any other way; hence the whole column produces the same degree of pressure as if it were at rest, and causes the atmosphere to press on the water above it in proportion to its whole height, in the same manner as if the pressure were derived in any other way from an equal column of water; and the case is reduced to a perfect analogy with the pressure of a head of water of this height, since the air acts upon the particles entering the tube in the same manner as the water does in more common cases. Had the result of the experiment been different, it would have been an exception to the general principle of the preservation of living force, or the equality of the potential ascent to the actual descent; for the water, moving with the velocity due to half the height only, would have been capable of ascending but to half the height. Description ; Description of DR. YOUNG'S Apparatus for illustrating the Doctrine of Preponderance, From the JOURNALS of the ROYAL INSTITUTION of ALTHOUGH there can be no doubt of the truth of the mathematical conclusions, which have been deduced little considered in practical this to show that the velocity of each is inferior to that the |