THE FARMER'S MAGAZINE. 



255 



stones is laid over tbe culvert, an inverted grassy turf 

 covers the stones, and the loose earth is levelled to the 

 top of the ground. In alluvial countries, where tiles are 

 used for the purpose of draining, the culvert is formed 

 by placing two longitudinal rows of large tiles made for 

 the purpose, which are covered by the usual fillings of 

 the drains. A largo tile is turned to receive each small 

 drain, and with stones an opening is left in the side wall 

 to receive the water from the small tributary drains, 

 which fall a few inches of declivity from their own bot- 

 tom to ..he large drain. This declivity ensures a free 

 discharge from the small drains, so that no stoppage can 

 happen. 



Few fields of drained land will discharge more water 

 than can be contained in a square culvert of one foot, 

 and when the large drain has a fall to keep the water 

 running, which is done by a very small declivity. The 

 covered drain will discharge the water into a brook or 

 rivulet, of which the depth must freely receive the water 

 that comes to be admitted, which must not rise above 

 the top of the culvert of stones or of large tiles. Each 

 trunk drain that receives water must be fitted for the 

 purpose of receiving the contents of the smaller provi- 

 sions of draining. The whole systematic value depends 

 upon this aptitude being adjusted and continuously up- 

 held. Any breach destroys the connection, and makes a 

 hurtful disruption. In every case a declining level must 

 be got and maintained throughout. The damage ceases 

 when water is delivered into a channel into which no 

 small drains are discharged ; the course may then be 

 more interrupted, and the waters move more slowly; 

 but where a general drainage occurs, every point must 

 be free and uninterrupted. 



In many cases the water from the small drains, after 

 escaping from the orifices, will traverse, before reaching 

 the river, all the intermediate trunks that have been 

 mentioned — brooks or rivulets, open cuts, and covered 

 drains. The last-mentioned conductor will convey the 

 water from the field where it is collected by the under- 

 drains, and discharge it into an open cut or brook, 

 which may immediately receive an adjacent small drain- 

 age into its current. The formation must be capable 

 not only of receiving a collected stream of water, and 

 conveying it along, but of reducing the top of the cur- 

 rent below the level of the adjacent small drainage, to 

 admit the contents fre|Jy and without impediment. It 

 is best that all small drainage of waters be collected by 

 a covered drain or open cut, and discharged by one mouth 

 into a brook or rivulet. The covered drain being firmly 

 erected no derangement can happen, and there is only 

 one orifice to be attended. This mouth of discharge 

 must have a very free outlet; and if it joins the receiving 

 current on a level, the direction must be turned to the 

 line of the main stream, and join it at a sharp angle. In 

 this way the currents are joined in the flowing of the 

 waters, and no pressure is exerted which can stop the 

 continuation of the moving fluid. When a brook re- 

 ceives the contents of small drains throughout the whole 

 course from the mouth of covered drains to the passage 

 into the main river, the importance is most evident that 

 the trunk afi'ords a ready acceptance and uninterrupted 

 conveyance to the collected burdens, which must not be 

 allowed to stagnate or lose the onward progress. When 

 the upper portion of a brook in its course is a receiving 

 trunk, and the lower part a conveyance of water, the 

 passage of the fluid will be less regarded in the latter 

 part ; the stream may be deeper, and the movement 

 slower and more sluggish. A depth of water will not 

 stop any discharge of small drains, and therefore the 

 course may be less regarded ; but in the upper part, 

 where the special purpose consists in the trunk receiving 

 and conveying ^-ater from the under-drainage of wet 

 lands, a most vigilant attention must be exercised to keep 



the current of water in constant motion, and the highest 

 level below the bottom of the drains, in order that a 

 free discharge be secured to every orifice of water. This 

 chief point is ever to be pushed forward for attention. 



The drainer who knows his business, on having deter- 

 mined the line of the small drains of any ground to be 

 perforated by cavities below the surface, will seek the 

 lowest point or points to which the collected waters will 

 fall, and look for the outlet by which the discharge must 

 issue. Having found this point, the examination will 

 proceed along the rivulet or brook, and ascertain the 

 efficiency of these trunks to receive and convey the 

 water ; if insufficient, the beds rau^t be improved as be- 

 fore directed ; and if the course be distant from the point 

 of the collected waters, an artificial open cut must be 

 made, to act as a connecting trunk. When a cut or 

 brook, or any secondary channel or water, reaches 

 another property of land, and finds insufficient out- 

 let, that property must provide a proper discharge for 

 the current, and transmit the water that comes for ad- 

 mittance. W^ater is a burden that must be received from 

 higher grounds by the lower situations, and conveyed 

 over the extent of the latter, not only without injury to 

 itself, but also to inflict no damage on the property from 

 which it descends. Every landed estate incurs this re- 

 sponsibility. 



Having reached the main outlet by which the collected 

 waters descend from the small drains to the river or 

 chief conveying trunk, the examination proceeds along 

 the rivulet or brook, observes every defect, and suggests 

 the remedy by marking every proper position. When 

 the river is reached, beyond which no inspection is re- 

 quired, the level of that receiving trunk is accurately 

 taken ; and if the backlying country is flat, the spirit 

 level is applied to denote the rise of every progress from 

 the river, in order to ascertain the descent that can be ob- 

 tained. In this way the descent is traced to the mouth of the 

 covered drain which discharges the collected waters ot the 

 under-drainage, and the cutting of each excavation accu- 

 rately determined along the whole course. The downward 

 progress from the highest-drained lands to the lowest 

 receiving trunk observes and inspects the courses of 

 water as they are presented to view, and satisfies the 

 inquiry of necessary outlets. The retracing of the steps 

 adjusts every connection of the streams, and puts the 

 whole arrangement into working order. 



It is advantageous that the trunk drainings that have 

 been mentioned are done for a time previous to the exe- 

 cution of the small drainage that must discharge the col- 

 lected waters into the channels of conveyance. In all 

 situations where the fall that can be got does not amount 

 to a descent of running water, but barely moving or 

 slightly removed from stagnation, the previous perform- 

 ance of the trunk drains will afford an inspection of the 

 sufficiency of the executions for the intended purposes. 

 If the regular descent is anywhere interrupted, and a 

 stoppage is perceived, the whole line of conveyance must 

 be again very accurately surveyed, and the levels ascer- 

 tained, by what means and in what places the remedy is 

 to be applied, in order to remove the deficiency that ex- 

 ists, and to promote the intended object. Deepening of 

 the beds of water-courses can only be done in summer, 

 when the quantity of water is small and the channel 

 nearly bare ; hence the intervention of one summer at 

 least is necessary in such cases, that an opportunity may 

 be given of deepening the bed of any brook, rivulet, or 

 open cut that has been seen to be too shallow during the 

 floods of winter. At least one year should elapse from 

 the execution of trunk drains to the performance of small 

 drainage ; and both purposes being done in summer, a 

 winter will intervene to show the capability of the con- 

 ducting channels, and the rectification can be performed 

 during the summer of the small draining. An elevated 



