oir 





I'KMXAOE. 



may also the coramunioatioas to parliament, by the Commissioners 

 appointed to Report upon the nature and extent of the Irish bogs.' 



A system of drainage ndnsively by open cut* ia, at the present day, 

 so ran in our own country, and in fact in all countries, where there is 

 the ordinary variety of hill and dale, that the meaning of the generic 

 term, Asany, IMS almast beta perverted to that of a subterranean 

 Cher* are. however, very essential differences between the 

 hiefa ara adapted to these respective mode* of operation, 

 therefore to admit any confusion in the names 



and it is 



by which thy~ar characterised. One of the most important of these 

 illnViamss arum (root the tact that in open drainage little reference 

 nead be made to the daily rain fall, provided the outfall be established 

 under such conditions as to prevent any serious accumulation of water, 

 whilst the rain-fall of the particular d'utriot will regulate the 

 Bora to be given to a series of subterranean drains, in connection 

 with the usual connderations with respect to the permeability of the 

 strata. It usually happens alao that little reference need be made 

 to the permeability of the low lands, to which alone the open out 

 drainage can be economically applied ; because the level of the water 

 in the cuts is usually maintained at a permanent line, and it is only 

 the excess of water which is removed. In fact, in the district* 

 wherein drainage is effected by open cut*, the class of cultivation is 

 usually such aa to require the presence of a definite quantity of water 

 in the lubsoil, and, in the polders of Holland especially, very serious 

 evil results from an abnormal lowering of the wau-r line. In district* 

 wherein subterranean drains are used, however, it is essential to remove 

 M rapidly as possible any water* which might have a tendency to 

 stagnate around the roots of the plants, or to prevent the surface of 

 the ground from being cooled by the rising of spring*. The practical 

 detail* of the two systems of drainage are naturally much affected by 

 these peculiar local conditions, and in the case of the subterranean 

 drainage the physical outline* of the country will further affect the 

 question, by reason of the greater or less facilities they offer for the 

 throwing off, or retaining surface water*. 



In properly drained land, situated at such levels as to allow the water 

 collected in the outfall drains to flow freely, the surface of the ground 

 is always dressed into such tables, or ridges, as to ensure the discharge 

 of the water falling from the atmosphere which does not permeate the 

 surface itself ; and the drains have only to carry off the water which 

 oaks through the ground. Evidently, under such circumstance*, the 

 drains must be placed at distances varying according to the degree of 

 permeability of the ground, and also of the nature of the subsoil, 

 though the latter condition would rather affect the depth of the drains 

 than their lateral distances. Some discussion has taken place amongst 

 the leading professors of the art with respect to these details ; but they 

 seem to have simply fallen into the error of all absolute theoreticians, 

 for it must evidently be absurd to apply indiscriminately any system 

 of either deep or shallow drain* ; and it must as evidently be the proper 

 course to modify both the depth and the distance apart of the drains, 

 according to local circumstances. 



The only invariable condition affecting the depth of drains i, that 

 they must be beyond the reach of any agricultural operations. In 

 light lands the plough often does not descend more than 8 inches, and 

 even in the most fertile districts of the North of Spain not more than 

 4 inches ; whilst in heavy stiff clays, as in the island of Jet 

 depth of the plough is not less than from 18 to 20 inches. It is there- 

 fore customary t > place the drains, even in what is called shallow 

 drainage, at a minimum depth of from 20 to 24 inches, measuring 

 from the top of the material constituting the channel to the surface of 

 the ground. The maximum depth at which drains are laid does not 

 exceed under any circumstance* from 6 to 8 feet, and it is only occa- 

 sionally that the depth is made more than 4 feet 8 inches from the sur- 

 face. In shallow drainage the number of the drains is increased, and 

 they are brought closely together ; whilst in deeper drainage the distance 

 is augmented. Smith of Deanstonc, who was an advocate for shallow 

 drains, usually made them from 6 to 8 yards apart, and about 8 feet 

 deep. Parkes recommend*, on the contrary, that the distances asunder 

 should be made from 1 3 to 20 yards, and that the depth should be 

 nude from 4 feet 6 inches to 8 feet. The choice of the respective 

 systems must, however, be regulated by the nature of the subsoil a* 

 much as by that of the soil itself, and very careful observations should 

 be made before either of them is adopted. 



The width of the trenches will be regulated by the depth of the 

 drain rather than by any other condition, for it must be made wide 

 enough to allow the workmen to perform easily any of the op. 

 required for levelling the bottom of the excavation, or for ; 

 the pipes or other material*. In practice it is found that, for a depth 

 of 8 feet, it ia sufficient to give a width of 1 foot at the surface and 

 > feet at the bottom ; for a depth of about 4 feet, these widths become 

 respectively 1 foot 4 inches and 8 inches ; whilst for a depth of 8 feet 

 they become respectively 2 feet 6 inches and 1 foot 2 it. 

 hard resisting grounds, which are not likely to cave in, a* the workmen 

 say. The width of the tx,' ),, it i* to be observed, ia 



regulated rather by the necessity for it* being sufficiently 

 enable the workmen to lay the pipes than by any other condition ; and 

 it I* also found, practically, that it is not possible to secure the regu- 

 larity of the inclination of the bottom, unless the men can stand 

 diredlv nprm it. The success of a system of drainage depends greatly 



upon the last-named condition, namely, the regularity of the incli- 

 nation, as also upon its being made such as to ensure the constant flow 

 of the water. Generally speaking, a fall of 1 in 200, in the minor 

 drains, will suffice, especially when the drain-tiles have been well and 

 carefully laid. 



It is not desirable to make the sub-drain* of any great length if th. ir 

 "ii should be considerable ; because, under such circumstances, 

 it is possible that the head of water in the pipes or channels might 

 burst them, and there ia always danger of an accumulation of silt. 

 Generally speaking, the smaller drains do not exceed 100 yard* in 

 length before discharging into snbmains of larger dimensions ; and the 

 latter are limited to a length of about 800 yards before discharging 

 into open ditches, or into the main outfall of the district. If it were 

 possible, it would even be preferable to make the small pips* or chan- 

 nels themselves discharge into the open ditches, without using any 

 sub-mains. An important remark to be made with regard to every 

 description of subterranean channel ia, that they must be carried aa far 

 as possible from trees or hedges ; because the roota of the latter have a 

 remarkable avidity for water, and they are sure to find their way into 

 any channel in tlieir immediate neighbourhood. The sub-mains should 

 be laid a little below the ordinary line of the smaller channels, in onli-r 

 to communicate to the water a greater velocity when it approaches the 

 point of junction ; and the junctions should be made with a curve 

 r,p !. the plan, so as to avoid any direct interference with the lines of 

 flow of the respective streams. 



There are several modes employed for the purpose of filling in the 

 trenches of drains, the choice of which must be regulated by local con- 

 iliti >ns of economy; though, as a general rule, it would unquestionably 

 be better to resort to the use of pipes of stone or of earthenware. The 

 cheapest, but also the least permanent, mode nf forming the channel 

 consists in cutting a species of shoulder near the bottom of the i 

 upon which a thick sod of the grass from the surface is laid, with the 

 grass downward*, and then filling in the remainder of the trench with 

 light permeable earth. In countries where stones are easily obtained, 

 it is customary to use them for the purpose of forming the channel ; 

 and this is effected by placing two slabs in an inclined po- 

 another, and covering them to a certain height with the smaller broken 

 stones. Both the stone and the turf channels are, howv 

 become silted up, or even to be choked, by the precipitation of the 

 salts which the water* may hold in solution; and it is on these accounts 

 that agricultural engineers have, of late, given very decided pri : 

 to the use of tile or pipe drains. Formerly the tile and shoe drains 

 were the most generally used ; and, in filling them in, it was customary 

 to lay flat tiles or shoes at the bottom of the trench, which 

 made about 14 inches long and about 5 inches wide, and upon them to 

 place the tiles, of the same length, and from 8 to 4 in.-h-.- wide and 

 4 or 5 inches high. Of late years cylindrical tubes have been almost 

 exclusively used, not only on account of the economy of their manu- 

 facture, but also of the greater ease and regularity with win. 

 can be laid. These pipes are made of almost any diameter, from 

 1 foot to 1 inch, and of lengths varying from 14 inches in the M 

 dimensions to 2 feet in the larger one* ; the 2 inch pipes being gene- 

 rally used for the small drains, and the 4 or 6 inch pipes for sub-mains 

 under normal conditions. When cylindrical pipe* are used in peaty or 

 very moveable soils, it is necessary to protect the abutting joints by 

 means of collars ; but in ordinary soils no such precautions arw required 

 to be observed. Drain-pipes of ordinary brick or tile earth are made in 

 almost every county in England by a very simple species of mat! 

 and they are burnt iu close kilns, the prices in the maker's yard being 

 usually about as follows : For pipes, 



1 in. diam., the price is ti. Oil. per 1000, and a cart with 4 honescan carry 8006 

 U ,. 80 ,, ;ooo 



If 80 ., JOOO 



24 10 ,, 3500 



2} U 3000 



In the most economically constructed tile factories, indeed, it appears 

 that the outlay upon plant is so small, that almost any large ! 

 proprietor would have a direct interest in making tile* on his own 

 it. The total expense of a Scragg's pipe-making machine, a 

 pug-mill, drying-shed, and kiln to hold 40,000 tiles, would, according to 

 Captain Johnston, not exceed 220/. 



It may be here added, that the ordinary cost of pipe-drainage in 

 clay land will vary, according to its more or less permeable nature, 

 between 21. \Qt. to 5i per acre : in rocky ground, of course the coat 

 would be increased, but fortunately drainage i* rarely required in such 

 positions. 



In town drainage it is important to observe that the system to be 

 I n]ion the consideration as to whether or not the 

 surface or rain waters ore to be carried off simultan !. those 



furnished by the houses to which all modem improvement* ore applied. 

 Drainage in itself is indeed distinct from sewerage ; and the u, 

 which are adapted for the one operation may be vei 

 the other a f.i<:t which unfortunatily has I ^.J by the 



ollicial authority a who ' assumed to teach local boards how 



they ought to execute sanitary works. For many reason* it will Ill- 

 prefer.. . r the consideration of this subject to the article 

 SEWERAGE ; but it may be necessary here to observe that, especially in 

 case* where a town may be situated upon the outcrop of a permeable 



