3101. High-pressure turbines for every 10-horse power. We have seen, S.-E. of Dedham, in Essex, England, a small stream collected for a few days, in a reservoir, thence passed on an over-shot wheel, and again on an undershot wheel. If possible, let the reservoirs. be surrounded by shade trees, to prevent evaporation. 310K. Artesian Wells may be sunk and the water raised into tanks to be used for household purposes, irrigating lands, driving small machinery, and extinguishing fires. 310L. Reservoirs are collected from springs, rivers, wells, and rain-falls, impounded on the highest available ground, from whence it may be forced to a higher reservoir, from which, by gravitation, to supply inhabitants with water. 310P. Land and City Drainage. In draining a hilly district.—A main drain, not less than 5 ft. deep, is made along the base of the hill to receive the water coming from it and the adjacent land; secondary drains are made to enter obliquely into the main, these ought to be 4 to 5 ft. deep, filled with broken stones to a certain height; tiles and soles, or pipes. The first form is termed French draining; the last two mentioned are now generally used. 1838 to 1842 we have seen, near Ipswich, England, drains made by digging 4 feet deep, the bottom scooped 2 to 3 inches and filled with straw made in a rope form, over this was laid some brushwood, then the sod, and then carefully filled. In The French drains were sometimes 15 inches deep, 5 inches at bottom and 8 inches at top, all filled with stone, then covered with straw and filled to the top with earth. In tile draining the sole is about 7 inches wide, always 34 in. on each side of the tile, and is about 12 to 15 inches long, its height is to be one-fourth its diameter. The egg shape is preferable. Never omit to use the tile, let the ground be ever so hard. Pipe Drains.-Pipes of the egg shape are the best; pipes 2 to 4 in. diameter have a 4 in, collar. In retentive land put 4 feet deep and 27 feet apart; when 31⁄2 feet deep, put 33 feet apart. From the best English sources we find the comparative cost. 21⁄2 ft. deep cost 31⁄2 pence, add 11⁄2 pence for every additional 6 inches in depth. Profit by thorough drainage is 15 to 20 per cent. See Parliamentary Report. 310Q. In draining Cities and Towns our first care is to find an outlet where the sewage can be used for manure, and to avoid discharging it into sluggish streams. The result of draining into the river Thames, and the Chicago river with its far-famed Healy slough ought to be suf ficient warning to Engineers to beware of like results. (See Sec. 310J.) Where the city or town authorities are not prepared to use the sewage as a fertilizer, and that there is a river near, or through it, let there be intercepting sewers, egg-shaped, with sufficient fall to insure 21⁄2 feet per second, which in London is found sufficient to prevent deposit; should not exceed 41⁄2 feet per second. When these main sewers get to a considerable depth, the sewage is lifted from these into small, covered res ervoirs, thence to be conveyed to another deep level, and so on until brought far enough to be discharged into the river, or some outlet from which it cannot return. But we hope it will not be wasted; the supply of Guano will fail in a few years, then the people will have to depend on the home supply. Sewers under 15 inches diameter are made of earthenware pipes, with collars, laid in cement; 2 foot diameter are 4 inches, or half a brick, thick; 3 to 5 feet, 8 inches thick; 6 to 8 feet, 12 inches thick, according to the nature of the earth. Where the soil is quick-sand, the bottom ought to be sheeted, to prevent the sinking of the sewer. As the sewers are made, connecting pipes are laid for house drainage at about every 20 feet, and man-holes at proper intervals to allow cleansing, flushing, and repairing. A plat is on record, showing the location of each sewer, with its connections, man-holes, and grade of bottom, to guide house and yard drains or pipes, whose fall is one-quarter inch per foot, in Chicago. 3100. Irrigation of Land. In wet distrets the land is cut up in about 10-acre tracts; the ditches deep; ponds made at some points to collect some of the water, these ponds to be surrounded by a fence and shade trees, such as willow and poplar, a place on the North side of it may be sloped, and its entrance well guarded with rails, so that cattle may drink from, but not wade in, the pond, which may be of value in raising fish. v = 55 2 af and Q va. Here >= vel. in feet, it == area, and f fall in feet per mile. In irrigating, the land is laid off and levelled so that the water may pass from one field to another, and may be overflowed from sluices in canals fed from a reservoir or river. The water from a higher level, as reservoir, may be brought in pipes to a hydrant, where the pressure will be great enough to discharge, through a hose and pipe, the required quantity in a given time. Water or sewage can be thus applied to 10 acres in 12 hours by one man and two boys. The profit by irrigation is very great,-witness the barren lands near Edinburgh, in Scotland, and elsewhere. In England, on irrigated land, they grow 50 to 70 tons of Italian rye grass per acre. Allowing 25 gallons of water to each individual will not leave the sewage too much diluted, and 60 to 70 persons will be sufficient for one acre, applied 8 times a year. At the meeting of the Social Science Association in England, in 1870, it was decided that the sewage must be taken from the fountain head, as they found it too much diluted, and that alum and lime had been used to precipitate the fertilizing matter, but had failed. They estimated They estimated the value due to each person at 8 shillings, but in practice realized but 4 to 5 shillings. Mr. Rawlinson recommended its application diluted; others advocated the dry earth closet system, which in small towns is very applicable, owing to the facility of getting the dry earth and a market for the soil. 310R. The supply of guano will, in a few years, be exhausted, then necessity will oblige nations to collect the valuable matter that now is wasted. See Sec. 3101. H Р D horse-power capable of raising 33000 pounds 1 ft. high in 1 minute. pressure in pounds per square inch. diameter of cylinder piston in inches. A = area of cylinder or its piston. length of stroke, and 2 S total length travelled. mean vel. of piston in feet per minute. total gallons (Imperial) raised in 24 hours. quantity raised by each stroke of the piston. pounds of coal required by each indicated horse-power. indicated horse-power. The American Engineers add one-third for friction and leakage. Example. The required gallons in 12 hours 3,000,000; Stroke, 10 feet; number of strokes per minute 12; time in minutes = 1440. From the above, we find q 173.6 Imperial gallons; d 22.6 inches-the diameter of the pump, as taken by the American engineers; d 22, as taken by the English. For much valuable information on the steam engine, see Appleton's (Byrne's) Dictionary of Mechanics, and Haswells' tables. Average duty of a Cornish engine is 70 million lbs., raised one foot high, with 112 lbs. of bituminous coal. Example. From Pole on the Cornish Engine, as quoted by Hann on the Steam Engine. Cylinder, 70 inches diameter; stroke, 10 feet; pressure per square inch, 45 lbs. during one-sixth the stroke, and during the remainder the steam is allowed to expand. This is the work performed before the steam is cut off. To find the work done by expansion.—Find from a table of Hyperbolic Logarithms for C 1.7916, which, multiplied by the work done before the steam is cut off, will give the work required, that is, 1,7916 × 288600 Work done after the steam is cut off, 517102 310. 310T. Pressure of Fluids and Retaining Walls. (DEF.-Retaining Wall is that which sustains a fluid, or that which is liable to slide.) The Centre of Pressure is that point in the surface pressed by any fiuid, to which, if the whole pressure could be applied, the pressure would be the same as if diffused over the whole surface. If to this centre a force equal to the whole pressure be applied, it will keep it in equilibrium. Against a rectangular wall the centre of pressure is at two-thirds of the height from the top, and the. In a cylindrical vessel or reservoir the same formula will hold good, by substituting the circumference for the length, 7, of the plane. P Example.-For a lock-gate 10 ft. long, 8 ft. deep, the pressure 64 2 × 10 × 62.5 20,000 pounds. Example. For a circular reservoir, diameter 20 ft., depth 10 ft., filled with water, we have 2 10 × 10 × 20 × 3.1416 × 62.5 P 196,350 lbs., the pressure on the 20 x 20 x .7854 × 62.5 19,635 lbs. sides of the reservoir. The pressure on the bottom Total pressure, 215,985 lbs. Dams are built at right angles to the stream entering the reservoir. All places of a porous nature are made impervious to water by clay or masonry laid in cement; top to be 4 ft. above the water; width, in ordinary cases, equal to one-third the height; the inner slope, next the water, to be 3 to 1; the outer slope 2 to 1. In low Dams, width at top equal to the height. Dams, in Masonry, by the French Engineers, Morin and Rondelet, ot bottom 0.7 h, at middle, 0.5 h, and top, 0.3 h. 3107. Thickness of rectangular walls is found from H total height, and h height from top of dam to water. Foundations of Basins and Dams are to rest on solid clay, sometimes on concrete, laid with puddled clay. The side next the water is laid with stones 12 inches deep, laid edgewise; sometimes they are laid with brick in cement, the outer face covered with sod. A puddled wall is brought up the middle whose base one-third the height, and top one-sixth the height; the top is made to curve, to carry off the rain water. Waste-weir is regulated with a waste-gate, and made so as to carry off the surplus water; the sluice or gate may be made self-acting. Bywash receives the surface water from the waste-weir, and from the supply streams when not required to enter the reservoir in times of heavy rains and when the water becomes muddy. 310M. Cascade. Let f fall from crest of weir, h, as usual, the height of still water above the crest of the weir, v 5.35 and a 4 3 N kj = distance to which the water will leap; this distance is to be covered with large stones, to break the fall of the water. 310t. Retaining Walls are sometimes built along the base of the dam. St. Ferrel Reservoir, destined to feed the Languidoc Canal, in France, contains 1541 million gallons of water; the dam at its highest part is 106,2 feet. One reservoir in Ancient Egypt contains 35,200 million cubic feet of water. Some are in Spain holding 35 to 40 million cubic feet-similar ones are found in France. The Chinese collect water into large reservoirs for the supply of towns and cities, and the irrigation of their lands. The Hindoos have built immense reservoirs to meet the periodical scarcity of rain, which happens once in about five years. One of their reservoirs, the Veranum, contains an area of 35 square miles, made by a dam 12 miles long. The evaporation in India for 8 months is 1⁄2 inch in depth per day. One-fourth of an inch may be a safe calculation in milder or colder climates. In Dams of Masonry, buttresses are made at every 18 to 20 feet. Depth the thickness of the wall, and length double the thickness. Mahan and Barlow, in their Treatise on Engineering, say, "It is better to put the material uniformly into the wall." 310U. To find the thickness of a rectangular wall, A B, to resist its being turned over on the point D. (See Fig. 70.) Let the perpendicular, E F, pass through the centre of the rectangle; by Sec. 313 it passes through the centre of gravity G, makes C P pressure weight of the wall, the pressing fluid or mass. one-third of B C. We have the vertical and the lateral pressure equal to that of Let w specific gravity of the water, and W that of the wall. We have the pressure of the fluid represented by HD = C P, and that of the wall by D F, and TDH is a bent lever of the first order. We have the value of P × 2 B C per lineal foot, and find the value of 3 W for height, BC, and one foot thick, which, divided into P × 2 BC, will give the value of A B or DC when on the point of turning over. Let w weight of material, and S weight of water; h that of the water, and b breadth of wall required, then we have wall = height of |