374 



THE FARMER'S MAGAZINE. 



ON DRAINING. 



BY JOHN EWAET, 



LAND SURVEYOR A\D ACRICULTCT.AL ARCHITECT AND EXOINEER, NEWCASTLE-UroN-TVXE. 



The object of the present paper is to point out 

 hydraulic principles necessary to be understood, and to 

 give rules for calculating results required to be arrived 

 at in the efficient draining of land. Such principles and 

 calculations are frequently neglected to be carried into 

 practice by those who undertake so important an 

 element of agricultural improvement, and which neglect 

 has almost invariably resulted either in inefficiency or in 

 needless expense being incurred. 



To demonstrate the rules to be met with in the pre- 

 sent article would obviously trespass too much on the 

 pages of a periodical publication on which there must 

 always be considerable demand on its space for matter 

 of varied topics, therefore such demonstrations are 

 omitted ; besides which, the rules in question are mostly 

 of so simple a nature as to be easily investigated by 

 those readers who may have any knowledge of 

 mathematics ; and to those who may be wholly ignorant 

 of the science, demonstrations would not only be un- 

 interesting, but wholly useless. 



For the first of the above-mentioned reasons tables 

 of the results of the calculations have been omitted, 

 and also because the rules themselves are, for the most 

 part, 80 concise that the labour in making calculations 

 in any case that may arise will be found to be inconsi- 

 derable. The tables referred to in the rules being 

 found in most books treating of elementary mathe- 

 matics, it will be unnecessary to reprint them, even if 

 such matter were suitable for these pages. 



Having in the foregoing preface explained the reasons 

 for omission of matter, which to many readers may ap- 

 pear to be important, the subject of the present article 

 may be proceeded with. 



Land draining may be classed under three distinct 

 systems. 



The first is that called Trunk Draining, and consists 

 in the improvement of estuaries and tidal rivers in the 

 discharge of their waters into the sea ; the increased 

 discharge of the waters of streams and rivers beyond 

 the action of the tide ; and the formation of open cuts 

 to receive the water collected by covered drains, and to 

 discharge it into natural watercourses and streams. 



The second system consists of the removal of under- 

 ground water by the tapping of land springs. 



The third system is that known in difi'erent localities 

 as frequent draining ^ from the frequent occurrence of 

 the drains in the soil ; thorough draining, from its in- 

 tended effect ; furrow draining, from the trenches being 

 in many cases made in the furrows of the lands ; and 

 parallel draining, from the drains collecting the water 

 in the soil being laid out parallel to each other. 



Before entering on the consideration of the different 

 systems of draining enumerated abovcj it may, perhaps, 



render subsequent remarks more perspicuous to glance 

 at the physical properties of water so far as they afFect 

 the subject under discussion. 



Were it not for its fluidity, water would, as regards 

 its motion, be subject to the same laws as solid bodies ; 

 but, on account of this property, the laws by which the 

 motion of solids are regulated require great modifica- 

 tion when applied to water. 



Fluidity is that property of a body, whose parts are 

 very minute, by which the yield to any force impressed 

 upon it, however small, and by so doing are easily 

 moved among themselves ; and therefore the body is 

 incapable of assuming any definite form. 



A property of water is, that it is nearly wholly in- 

 compressible, so much so, that for all practical purposes 

 it may be considered perfectly incompressible. 



All fluids have not the same degree of fluidity, ac- 

 cording to the facility with which their particles may be 

 moved amongst each other. Water and mercury may 

 be classed amongst the perfect fluids. Many others, 

 such as oil, mucilage, and such like, have a consider- 

 able degree of tenacity, are therefore imperfect fluids, 

 and that property known by the term viscous. 



A cubic foot of distilled water weighs at ordinary 

 temperature of the atmosphere of Great Britain 1,000 

 ounces or 62^ lbs. avoirdupois ; and rain or spring 

 water in its usual state of purity may be taken at the 

 same weight ; consequently there are 35.84 cubic feet 

 to weigh one ton. 



A column of water 1 inch square of horizontal section 

 weighs 0.434 pound avoirdupois for every foot of its 

 height. 



A cubic foot contains 6.23 imperial gallons, and a 

 cylindrical foot 4.9 imperial gallons. 



When the atmosphere presses on the surface of the 

 earth with a force of 15 pounds to the square inch, it 

 balances a column of mercury of nearly 30 inches, or a 

 column of water 34.56 feet in height. 



The quantity of water in one inch in depth of rain 

 fall on an imperial acre of surlace is 3630 cubic feet, 

 which is 22B22. 523 imperial gallons, or 101.28 tons. 

 Water solidified in the state of snow in the climate of 

 Great Britain is increased to six times its bulk, or six 

 inches depth of snow fall is equivalent to only one inch 

 depth of rain fall. 



Water, when contained in a vessel, presses against the 

 sides of the same equally with a pressure of one-half 

 that with which it presses the bottom, such pressure 

 being distributed over the whole surface of the sides ; 

 while the lateral pressure on the bottom of the sides of 

 the vessel is equal to the perpendicular pressure on the 

 bottom. 



The point of pressure, or that point in which the 



