Shoal water

“ Vast numbers of birds of different kinds were flying to the westward of the shoal, so that there probably is an island near that situation. The east part of this shoal is situated in 173° 12' east longitude, and the south part of it in 15° 50' south latitude, but how far it extends to the westward and northward is very uncertain, though doubtless to a considerable distance, as the water had a white appearance from the mast head as far as the eye could reach. Being now entirely free from the shoal, they stood to the northward, with a light easterly breeze, and moderate weather. ”

“ As no sea can be supposed absolutely motionless, the presence of a shoal, by casting up to the surface water which, but for it, would have continued to sweep along at a greatly lower level with the general body of the current, must bring the temperature of the surface water into nearer correspondence with that below. In low latitudes the surface water is hotter than that below; and accordingly it is a general remark, that the temperature sinks as the water shoals, or even in passing over banks whose depth is very considerable. ”

“ In daylight the danger is not nearly so great, because the north-eastern and north-western edges of the shoal are fringed by a number of cays among which the sea breaks heavily, while the whole surface of the shoal is white water. ”

“ They were distinctly seen under water, particularly a large white mass of rock, in 41/2 fathoms, having from 5 to 61/2 fathoms round it. The shoal was traced in 7 fathoms, on detached rocks, near the edge of it, having deeper water between them. On the southern edge of the shoal, from S.E. to W., the depth increases gradually to 30 fathoms, at the distance of half-a-mile from the shoalest part. ”

“ Removal of Shoals.—The possibility of securing uniformity of depth in a river by the lowering of the shoals obstructing the channel depends upon the nature of the shoals. A soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. ”

“ The countless shoals which annually coast the shores of Europe and America are not so interesting to the student of nature, as the more fertile law itself, which deposits their spawn on the tops of mountains, and on the interior plains; the fish principle in nature, from which it results that they may be found in water in so many places, in greater or less numbers. ”

“ The first thing is to put them in soak. This is done by carrying them down at low tide, and making them fast, in small piles, by ropes, and letting the tide come up and cover them. Every day we put in soak twenty-five for each man, which, with us, made a hundred and fifty. There they lie forty-eight hours, when they are taken out, and rolled up, in wheelbarrows, and thrown into the vats. These vats contain brine, made very strong,— being sea-water, with great quantities of salt thrown in. This pickles the hides, and in this they lie forty-eight hours ”

“ The lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. The removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. ”

“ Into this opalescent scene, some days before the freshet reached its height, the logs began to come down. In the upper country every tributary stream was pouring them out in shoals,—heavy, blind, butting, and blundering shoals,—to be carried by the great river down to the booms and saws above its mouth. Some, caught in eddies, were thrust aside up the bank to lie and slowly rot among the living trees. But most, darting and wallowing through mad rapids, or shooting falls, or whirling and circling dully down the more tranquil reaches of the tide, made shift to accomplish their voyage. ”

“ This drains off from the surface, forming rills, which collect as they descend, by their own weight, into the lowest channels of the ground, and form into streams and rivers, and back into the sea comes the water which the air had taken away, with this difference, that it is free from salt and fit for the many uses to which fresh water alone can be applied; when the vapour rises from the sea, none of the saline matters rise with it, for, although the water is volatile, yet they are not, and this is the whole source of fresh water. ”

“ They are formed by the deposit of particles of soil brought down into the main river by its tributaries, or by occasional streams created by the melting of the snow, or heavy rains. A shoal is first formed, which, as it accumulates, rises gradually above the ordinary surface, while the stream itself, if it flows like the Connecticut through a soft soil, is continually deepening its bed, and leaving these newly-formed banks out of the reach of accidental floods. ”

“ The filtration of water may now be considered. The water of our wells is presented by nature ready filtered to the hand of man, and often exhibits an admirable degree of transparency and purity. It acquires this state by percolating through the mineral strata of the earth, which deprives it of the organic matter it derives from the soil and subsoil, but, at the same time, it dissolves a portion of the saline and earthy media through which it passes, and hence acquires that peculiar ‘hardness’ which is constantly found in spring water. ”

“ The tide flows up the river many miles past the waterworks, carrying up with it the filth from the sewers. The supply of water was, to be sure, obtained when the tide was down, but as the banks of the river are clothed with sedges in many parts, and its bottom deep with mud, the water can never be free from sewage. ”

“ Fish which swim in shoals are not much produced in the rivers, but are bred in the lakes, and they do as follows:—When there comes upon them the desire to breed, they swim out in shoals towards the sea; and the males lead the way shedding forth their milt as they go, while the females, coming after and swallowing it up, from it become impregnated: and when they have become full of young in the sea they swim up back again, each shoal to its own haunts. ”

“ More than half of them were full—full to the very bung.
But what were they full? That was the serious question. Of fresh-water? No. The appalling discovery that had been made was, that the water within them was salt! in fact, water out of the sea itself, salt as brine!
This was indeed a fearful discovery; but it was easily explained. It was known from the beginning that these butts had been filled with salt-water—to serve as ballast on the out voyage from England; and the intention had been to empty them all into the African river and substitute fresh-water instead. ”

“ For first, the most excellent Governour, by His Divine Providence, hath most wisely ordained and appointed, that a salt water of this kind, which men could in no wise be without, should break forth out of the Earth, and it is thus effected: The Sea-water every where passing through the passages and clefts of the Earth, in some places is dried up by the Central fire, and coagulated into hard and great pieces, which being digged up by men, and dissolved by the help of Water, and freed from its fæces, is boiled up in fit Vessels, and reduced into a pure Salt. ”

“ Such a salt-water saucer of fresh water is maintained full to overflowing by the rainfall, and owing to the frictional resistance of the sand and to capillary action and the fact that a given column of fresh water is balanced by a shorter column of sea water, the fresh water never sinks to the mean sea-level unless artificially abstracted. ”

“ They come in great shoals; and they keep rooting the mud like hogs, and leave their trace in the form of large round holes.
They are very cunning; and when surrounded with a net, the whole shoal frequently escape by leaping over it; for if one takes the lead, the others are sure to follow. ”

“ For persons who are obliged to prepare temporarily the salt, as travelers passing through the country, the water of the lake, without concentration, may be used for washing out the deliquescent chlorides, sprinkling the heap of salt by a watering-pot at intervals of two or three hours during a single day, and allowing it to drain and dry at night, and be spread to the sun an hour or two the following morning. ”

“ At certain times they collect, presumably for breeding purposes, into shoals in the shallow water so dense as to form black patches 10 or 20 yards across, from which it is easy to collect a bucket-full in a few minutes by means of a sheet. ”

“ When a stream attains a place where its waters have to expand into the lakelike form, the current moves in a slow manner, and the broad surface exposed to the air permits a large amount of evaporation. If the basin be large in proportion to the amount of the incurrent water, this evaporation may exceed the supply, and produce a sea with no outlet, such as we find in the Dead Sea of Judea, in that at Salt Lake, Utah, and in a host of other less important basins. ”

“ The consequence of the ancient evaporation, by which the great Pleistocene lake was reduced to its present modest dimensions, and of the ceaseless modern daily evaporation, is the impregnation of the waters of the lake with salts and other mineral substances to a remarkable degree. Ocean water contains on an average 4-6% of salts: Dead Sea water contains 25%. ”

“ Hence we see the Benefit of frequently replenishing the Water with fresh Air, which we find is necessary not only to preserve the Life of [Pg 72] Land Animals, but also of Fish; as also the Use of their Gills, to spread in thin Sheets fresh Supplies of Water, that they may the better come at the Air in the Water; for which Purpose both Sides of their Gills are furrowed with many fine Furrows, not only thereby to enlarge their Surfaces, but also more minutely to divide the Water, whereby to come at the Air in it. ”

“ Waves, whether due to wind or other agency, may cause scour, especially of the banks. Their effect on the bed becomes less as the depth of water increases, but does not cease altogether at a depth of 21 feet, as has been supposed. Salt water possesses a power of causing mud, but not sand, to deposit.
Arts. 2, 3, and 6 of this chapter refer to action on the bed of a stream. Action on the sides will be considered in Art. 7.
Weeds usually grow only in water which has so low a velocity that it carries no silt to speak of, but if any silt is introduced the weeds cause a deposit. ”

“ In the dry season the evaporation, of course, increases the strength until the water can no longer retain the amount of salt in solution it therefore precipitates and crystalizes at the bottom in various degrees of thickness, according to the strength of the brine.
Thus, as the water recedes from the banks by evaporation and the lake decreases in size, it leaves a beach, not of shingles, but of pure salt in crystallized cubes, to the depth of several inches, and sometimes to half a foot or more. The bottom of the lake is equally coated with this thick deposit. ”

“ When first taken from the stone basin into which it flows, the water is perfectly clear and bright, and exhales no particular smell. It does not sparkle in the glass, but a few bubbles slowly separate, and adhere to the sides of the vessel. When it has stood for some hours exposed to the air, it becomes turbid, and otherwise undergoes a very material change. As it does not properly curdle soap, it may be denominated a soft water. ”

“ They swim in shoals, and bite freely at all hours of the day, but particularly on the rise of the water by flood or tide, and in warm weather, with a little wind, and are to be fished for with a strong line and good gut at the bottom, as some of them are large, and struggle much. ”

“ Hard water will become thick and foul sooner than soft water.
139. To purify Water for drinking.—Filter river water through a sponge, more or less compressed, instead of stone or sand, by which the water is not only rendered more clear, but wholesome; for sand is insensibly dissolved by the water, so that in four or five years it will have lost a fifth part of its weight. Powder of charcoal should be added to the sponge when the water is foul, or fetid. Those who examine the large quantity of terrene matter on the inside of tea-kettles will be convinced all water should be boiled before drunk. ”

“ The great beds of salt, deep in the earth, are usually accumulations left there by water that is drawn from brine lakes, from which the liberated water often escaped as pure spring water at the surface of the earth. It does not escape by evaporation, at least not until it reaches the earth's surface. ”

“ Its fresh air, and the air which follows the descent of the water-table, carries oxygen to the organic and [pg 025] mineral parts of the soil, and hastens the rust and decay by which these are prepared for the uses of vegetation. The water itself supplies, by means of their power of absorption, the moisture which is needed by the particles of the soil; and, having performed its work, it goes down to the level of the water below, and, swelling the tide above the brink of the dam, sets the drains running, until it is all removed. ”

“ In many lakes, and in the ocean, the quantity of saline matter is so great as to render it unfit for diluent purposes; but, when sea-water freezes, the saline impregnations are deposited; and the ice affords fresh water. In the state in which water is generally employed as a diluent, its impregnations are in small quantity, and not usually sufficient either to dim its transparency, or to give it color, smell, or taste, and consequently to render it unfit for the ordinary purposes of life. ”