THE FARMER'S MAGAZINE. 



877 



forward direction of a watercourse is scarcely apprecia- 

 ble in practice. 



If a watercourse have the sides and bottom tangents 

 to the semi-circle, of which the radius is the depth, and 

 of which form, it should be remarked, all watercourses, 

 the section of which is bounded by straight line, ought 

 to be, the breadth of the top will invariably be double 

 the length of the side. 



Having ascertained the velocity of current of a water- 

 course by the rule previously given, the discharge in 

 cubic feet is found by multiplying the velocity in feet 

 per minute or second by the area of the section in square 

 feet; which result, multiplied by 623, gives imperial 

 gallons, or, divided by 35*84, gives tons weight of 

 water. The area of section of water-courses is easily 

 found by the rules given in books treating of mensura- 

 tion. The most concise mode of finding the area of 

 circular segments is to divide the versed sine of the 

 arc of the segment by its diameter, and the number 

 corresponding to the quotient in a table of the areas of 

 segments of circles, of which the diametfr is 1, and 

 which is to be found in every treatise on mensuration, 

 multiplied by the square of the diameter of the arch, 

 or twice the depth of the water-course, is the area of 

 the segment of which the bottom or channel of a water- 

 course is an inverted circular arch. Such segmental 

 area must be added to the area of the trapezoid bounded 

 by the breadth at top, the sides, and the chord of the 

 inverted arch of the bottom, for the area of the section 

 of the water-course. Tables of the natural sines of every 

 degree and minute of a degree of a quadrant of a 

 circle are to be found in every treatise on trigonometry. 



The number of stock bricks laid dry, according to 

 the kind of work specified, in each course of a chain in 

 length, in lining water- courses, will be as follows, viz. : 



Flat as headers, height of each course 2| inches ,. 187 

 „ as stretchers, height of each course 2§ inches... 91 

 „ as stretchers, with every sixth brick a header, 



height of each course 2^ inches 103 



On edge as stretchers, with every sixth brick a 



header, height of each course 4^ inches . . 103 



Hollow bricks for inverted arch bottom, length of 



each 1^ foot 44 



The weight of stock bricks of the usual size is about 

 45 cwt. per thousand. 



The system of draining next in order for considera- 

 tion is the DEEP, or more generally known as the 

 Elkin'gton system, from Joseph Elkington, a farmer 

 at Stretton-upon-Dunsmore, in Warwickshire, by whom 

 it was discovered in 17G4, and by whom, and also by a 

 person named Smith, who, for that period, possessed 

 great geological knowledge, it was afterwards practised 

 with great success. So important were the discovery 

 and practice of these men deemed to be towards the 

 close of the last century, that Elkington was rewarded 

 with a premium of j£l,000 of public money, voted by 

 parliament in 1795 ; and Smith was honoured by having 

 the degree of D.C.L. conferred upon him by the Uni- 

 versity of Oxford. 



The system of draining in question is mostly, if not 

 entirely, for the purpose of draining springs, which, 

 until comparatively of late years, was considered to be 

 the sole cause of injurious wetnesa to the land. Before 



proceeding to describe the way in which Elkington's 

 system of draining was, and is as yet in some cases, 

 carried out, it may be well to offer some remarks on the 

 nature of springs. 



The proximate source of all springs is the absorption 

 of rain water and condensed meteorological vapours by 

 the soil, from which these pass into pervious strata of 

 the earth, in which the water accumulates, and follows the 

 dip until such strata appear at or near the surface, over 

 which the water flows until it finds another stratum of a 

 pervious nature, or is received into some other channel 

 by which it can pass — in the latter-mentioned case fur- 

 nishing the supply, first of insignificant burns ; tlien by 

 several such combining their contributions, and forming 

 rivulets ; and again, these combining, furnish the sup- 

 plies of large streams and rivers, by which the water of 

 springs is at last discharged into the ocean, the evapo- 

 ration from which is the original source of all water in 

 the land. Springs are frequently supplied from a 

 widely extended district of surface ; and it is, therefore, 

 not a necessary condition of their waters appearing at 

 the surface, that the strata in which they are contained 

 should actually crop out to the day, as it is frequently 

 the case that large springs by their pressure break 

 through rocks, banks of clay of considerable thickness, 

 and other impediments which oppose their progresa 

 along the strata in which they are contained. 



There are two kinds of springs — permanent or true 

 springs, and temporary springs. The true springs 

 furnish a constant supply of water at all seasons, 

 whilst the temporary springs either exist only during 

 wet weather, and are, in such cases, always at a higher 

 level than true springs ; or thoy are occasioned by the 

 leakage of true springs, when they appear at a lower 

 level than the main springs from which they proceed. 

 This is the reason why in sloping ground a true spring 

 is never found either at the top or bottom of a slope ; 

 and that temporary springs generally appear near the 

 top or bottom of rising ground. It should be remarked, 

 that temporary springs may be found boih at the top 

 and bottom of slopes. A temporary spring at a lower 

 level than a true spring is occasioned by a slip of the 

 stratum containing the main spring ; whilst a temporary 

 spring above the level of a main spring is merely the 

 outburst of water prevented, by some local impediment, 

 from passing from the absorbing surface to a pervious 

 substratum. 



The interception of outbursts of temporary springs 

 is never successful in effecting the complete draining 

 of land by the deep Elkington system. It is only 

 by passing through the true springs that efficiency 

 can be secured. It is, therefore, necessary that 

 drainers of springs should have an intimate knowledge 

 of the strata of the district, to be able to distinguish 

 true from temporary springs, and carefully investigate 

 the nature of the strata of the locality to be operated 

 upon, so as to mark well the bearings of the true springs 

 before determining upon the lines of drains. Without 

 such knowledge and precaution on the part of the pro- 

 jectors of such drains, great expense will be incurred in 

 the operation, to little or no purpose. 



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