80 



DRAINING. 



!ninu^. pit before the stratum cunt. lining wholesome water is 

 ^~""N""T' reached; and it it H!-O u-cd in mining lor pi,. teetion 



against a stratum, which emits hydrogen or ii 

 cruuiuU. ble air. A remarkable m-tancc of the former is rela- 

 ted in the Philosophical Transactions, vol. l\xi\. where 

 an account is given of sinking a well at Shecrneta. 

 When similar circumstances occur in boring for water, 

 the remedy is to introduce a pipe of wood or metal in- 

 to the Uire, which admits the water only at the lower 

 end. Nearly the same advantage is sometimes obtain- 

 ed, by excavating the hole a little wider in such I 

 turn, and pressing in clay, which the water in the bore 

 keeps from being displaced. I ft he water in the spring, 

 which is formed at (.'<, were confined by a surrounding 

 wall, it might be made to rise to the level of the origi- 

 nal outlet at E ; and a pipe might be laid from thence 

 to the top of the bank at m, so as to deliver water with- 

 out sinking a shaft diere, or boring for it; for in nei- 

 ther of these cases would it rise higher than the level 

 of C, if previously tapped there. Or the same water, 

 if abundant, may be applied to the working of machi- 

 nery, when a fall is in this way obtained for it. A ve- 

 ry pretty instance of dlis occurs at Cong, in the we-t 

 of Ireland, where the waters of the great Lough Mask, 

 issuing in a magnificent fountain, are dammed up by 

 a wall, and immediately applied to the turning of 



The effect of the bore at H, in this Figure, shows how- 

 wet grounds may sometimes be drained, by letting 

 down the water into an open stratum below them. The 

 most useful case of this kind, is that of a land-locked 

 bottom, into which the cutting of a main drain through 

 the bank would be attended with very great cxpcncc. 



Plate CCXXXI1I. Fig. 12. shows a case of this kind, 

 "' where the bog bottom, EGFg, is shut in by the high 

 '*' _ground L and M. These grounds, though composed 



of open rock or gravel, have a cover of clay at least on 

 die side next the hollow, through which the water can- 

 not descend, thereby forming a lake, or at least it de- 

 scends very slowly, so dial the bottom is frequently 

 under water, by which means it is converted into a 

 peat-bog or moss, and gradually fills up with dlis ve- 

 getable matter, until by dlis means, and the water 

 which it absorbs, die surface swells so fir, as to throw 

 the superfluous water oft' by means of the brook gh H ; 

 while die middle becomes a deep hobbling bog. inac- 

 cessible to man or beast, except when the sun and wind, 

 by evaporating part of die moisture, have formed a thin 

 crust on the surface. 



The obvious remedy is, to lower the outlet, or drive 

 a deep cut, or an underground tunnel, through the 

 ground M, into the lower part of the bason. But this 

 may be too expensive an operation. Examine whether 

 here is not an open stratum below the bason of clay, 

 or one which, if it should be glutted with water, may 

 yet be tapped somewhere, as at B ; then, in that case, 

 open a mam drain through die middle of die bog, with 

 cross and surface drains, to intercept and deliver the 

 water into die main. In this main there must be au- 

 ger holes sunk down into the open stratum ; these will 

 wallow up and carry off the water. Care must be ta- 

 ken to prevent die moss and clay from finding its way 

 into die swallow holes, which would soon choke them. 

 For dlis purpose, a filter of stones, or the like, must be 

 placed round them; or a pipe made of wood, slates. \ ( 

 to rise something above the bottom of the main drain, 

 which thus becomes a cess-pool. And that they may 



be a* little as possible lo.-uled with foreign v. .-!er-. f.mn ''" '"". 

 a catch-water round all the bottom in t 1 ~ ~"~ 



vcr. which may deliver the surf.i' , water of the neigh- 

 bouring grounds, by t!,,- original lowest outlet #/;. The K ', u ,. 

 surface of the bog will subside; but as all die drains 

 will subside with it. and the main drain most, they will 

 still continue effective. It is quite unnecessary to cut 

 such drains down to the 1 1. y bottom. 



One large pit or swallow -hole in the lowest part, 

 would answer equally well for u Ixig of limited extent, 

 if it could be carried down to the open str.itum ; ami 

 it would IK- less liable to choke. The main drain may 

 be led into it ; but the drainer nv.ist not expect the pcat- 

 be bled by such a pit alone, without the :issist- 

 iince of surface drain-. Swallow-holes are common 

 enough in the great bogs of Ireland, many of them of 

 great depth and magnitude, usually in limestone n>ck, 

 and they have obviously been formed after the bog had 

 accumulated ; yet they produce very little effect, even 

 very near them, though they may sometimes save ex- 

 pence in cutting drains. 



l)r Nugent, in his Travels in Cicrmany. 17<)<i, after 

 describing the mode of surface-draining the imxirs or 

 turf-ground >, mentions dlis " practice as of goo I effect, 

 and chiefly if the moors are not too wet and marshy. 



" It is the nature of moors in general, that beneath 

 the turf or moss there is a loam, which hinders the 

 moisture from penetrating ; and this, indeed, is what 

 makes the marsh, and causes the luxuriant growth of 

 die turf or moss; but this loam or clay is only a stra- 

 tum, and far from being of an immense depth. Under 

 it is generally a sand, or some other stony or loose 

 soil." 



Here reason informs us, that a middling morass may 

 be drained by perforating the clay, and thus make wny 

 for the moisture to penetrate. In order to effect this, a 

 pit is dug in the deepest part of the moor, till they come 

 below the obstructing clay, and meet with such a sjnrn- 

 gy stratum, as in all appearance will l>c sufficient to im- 

 bibe the moisture of the marsh above. Into this pit 

 the ebbing of the morass is com eyed through a trench, 

 and both the trench and pit are filled up alter the first 

 drain with large broad stones, setting them edgewise, 

 so as to leave interstices for the water ; then such stones 

 are laid over breadthwise, and these covered with loose 

 earth, like that on the surface. When no such stones 

 are to be had, strong piles are rammed down the sides 

 of the trench, and broad boards laid across, * and these 

 arc covered with eaith to a height fit for culture. 



" This is a matter of no great expence, the pit being 

 as near the morass as the water will admit, and the 

 trenches but short. Then they have a drain unpercei- 

 ved, which leaves the surface of the trenches for the 

 plough; and in middling marshes, especially m such 

 moors as are only wet and damp, this method, though 

 sometimes slow, never fails to take effect ; and many 

 tracts are thereby made serviceable to die farmer and 

 ie.r." 



The same practice is known in England. " If a pit 

 is sunk 'JO or 30 feet deep in the middle of a field, through 

 the Hertfordshire red flinty and impervious clay into 

 the chalk below, when the usual quantity of chalk is 

 taken out. die pit shaft is filled up with the flints ta- 

 ken out of the chalk and clay, and the top drainage of 

 dlis part of the fieldjnuch shortened for ever afterw .mis. 

 by making principal drains from the part of the field 

 above the !e\el of the top of die pit terminate therein, 



A wooden hollow drain. 



