supplement. AGRICULTURE AS PRACTISED IN BRITAIN. 1345 



water, will best attain their object when made straight up and down the slope. The reason is thus given 

 by Mr. Smith ofDeanston : " Drains drawn across a steep, cut the strata or layers of subsoil transversely, 

 and as the stratification generally lies in sheets at an angle to the surface, the water passing in or between 

 the strata, immediately below the bottom of one drain, nearly comes to the surface before reaching the 

 next lower drain. But as water seeks the lowest level in all directions, if the strata be cut longitudi- 

 nally by a drain directed down the steeps, the bottom of which cuts each stratum to the same distance 

 from the surface, the water will flow into the drain at the intersecting point of each sheet or layer, on 

 a level with the bottom of the drain, leaving one uniform depth of dry soil." (Remarks on Thorough 

 Draining, p. 9.) 



8314. Tile draining has the great advantage of suiting every soil, from the poorest to the richest, and 

 of being used at any depth, and where stones cannot be applied, as in morasses or flour-moss. It is less 

 expensive than stone draining, and equally, if not more, durable; for if a tile should give way, it can 

 easily be replaced, or a whole drain reopened and renewed at pleasure ; which is impracticable with stones. 

 Besides, being more portable, tiles can always be had of any size, shape, or strength desired, in those 

 clayey districts where stones are with difficulty procured, and may therefore safely be taken as the best 

 substitute for stones in ordinary draining. Shut up from the influence of the weather, and secured from 

 every injury, it is impossible to limit their duration, or conceive anything better calculated for the pur- 

 pose of draining. In all cases where the bottom of the drain has very little slope, tiles are decidedly 

 preferable to stone, and ought, therefore, to be used in such situations, even though they should prove 

 more expensive than stones. (Trans. H. S., vol. xii. p. 81.) 



831 5. Concrete drain tiles, have been made by Lord James Hay, and the mode of operation is most dis- 

 tinctly described and illustrated by figures in the Trans. H. S-, vol. xiv. p. 592. It can only be attempted 

 with any prospect of success where there is strong quick setting lime and sharp sand. Perhaps peat may 

 be advantageously compressed into draining tiles. 



8316. Peat cut like draining tiles by means of a peculiar spade, and dried in the sun during summer, 

 and stacked like peats ready for use, is found an excellent substitute for clay tiles. (Q. J. A., vol. vii. 

 p. 246.) 



8317. The substitution of larch.wood tubes for drain tiles has been adopted by W. Scott, Esq., Craigmoy. 

 Kirkcudbright. The tubes are 4 inches square externally, with a clear water way of 2 inches. They are 

 put together with wooden pins or nails, as may be found most economical. (Trans. H. S., vol. xiv. p 104.) 



8318. 4330. A tide sluice, invented by the Rev. George Cruden, is represented in figs. 1177. and 1178., 



, I 77 the first a vertical profile with the cover removed, and the second a 



' ' vertical section ; the same letters applying to both figures. 



d a, the spout of the apparatus laid in the embankment, con- 



structed of wood. 



b, the descending nozzle of the spout in which is placed the 

 float valve, also made of wood. 



c 



1178 



.- 



m 



< 



d c, the float valve, being a hollow wooden box capable of rising 



and falling in the nozzle b, from its buoyancy in the tidal water, 

 i so as to shut or open the passage a. 



d, openings for the escape of the collected water which is dis- 

 charged during the recess of the tide. 



The mode of the float's operation is thus : " During the recess 

 of the tide, the float, by its own gravity descends until its upper 

 surface is on a level with the sole of the spout, thus giving free 

 egress to the fresh water collected in the reservoir, until the 

 — ' flood-tide has risen so high as to envelope the float in its water. 

 The float is then raised by its buoyancy in the tidal water, and so closes the passage through the 

 spout a, preventing either the ingress of the tidal water or the egrses of the drained water until the 

 tide has again fallen below the level of the float. Perhaps a more uniform and more permanent action 

 would he obtained by constructing the float, and the chamber in which it operates, of thin sheet copper, 

 or of sheet iron, and giving it a cylindrical, instead of a cubical form. [Trans. High, hoc, vol. xii. 



P '8319.-4406. Sluices, trunks, and valves for embankments are now made of cast iron, on an improved 

 principle : and, when properly fixed in by a mass of masonry and cement, they are found to retain the 

 water of a pond, and admit it at pleasure, with as much accuracy and ease as a brass cock does the contents 

 of a beer barrel. , . ., . . , c . 



S320.—4485. Artesian wells, or those produced by boring, are so named from their having been first 

 used in the neighbourhood of Artes in France. Upon a review of the appearances observed m these 

 wells, it is quite evident that they must always succeed where an inclined stratum of a fissured or 

 porous limestone, or other porous stone, is included between two waterproof beds of clay ; one of w Inch 

 sets a 

 The i 



be penetrated, before reaching the spring v._, 



is never wanting. Although, for the most part, some thinner strata of limestone supply its place, jet 

 the strata, which conduct the water, always contain it in crevices, which are much more numerous on 

 the surface than in the centre of the beds. Thus, there is a demonstration, as in a boring work at 

 Blengel that, even in the limestone itself, beds of clay occur, rrom these circumstances it is easily ex- 

 plained how we can never hope to sink Artesian wells in granite, gneiss, porphyry, serpentina &C. 

 Even in schistose mountains, it would not be advisable to sink these wells because, if water were found 

 there it would be very easily impregnated with sulphuretted hydrogen, from the abundance of pyrites 

 occurring in these strata, and thus be unfitted for many uses. Limestone, on the contrary, which is very 

 insoluble, experience teaches us, yields a very pure water. These observations especially relate to the 

 Pms rf p CrIiis 



8321 Other districts, where water has been bored for, show a similar geognostic constitution to the 

 Pas de Calais. M. Gamier, in his Manuel du Fontamersondeur, $c., notices this, with regard to Boston 

 in America, and Sheerness in England. London (where many sugar-works distilleries and breweries 

 have for a long time, been principally supplied with water from Artesian wells) lies in the middle of a 

 basin-shaped hollow, the fundamental rock of which is a limestone belonging to the chalk formation ; 

 which also forms the heights in the vicinity, and which is covered with clay, though at times not imme- 

 diately. The wells, which are not sunk to this London clay, give abundance of clear, but mostly very 

 hard/water; while those which penetrate through the London clay, into the subjacent plastic clay, a 



ous limestone, or other porous stone, is included between two waterprooi Deus oi ciay ; one oi »mui 

 ; a limit to the sinking of the water downwards, and the other prevents it from rising above the surface, 

 e existence of such a cover is evinced by all boring works. A waterproof stratum ol clay must always 

 Denetrated, before reaching the spring water j and it may easily be conceived that the undermost laser 



narci, water ; w 1111*3 uiu>c wun.11 ucmruan. n.i^i. t ,.. v..-^ — — j , -■ — - - - - 



formation immediately covering the chalk, and consisting of alternating beds ^.^'^ & J'^°°^^' 

 yield a very soft and pure water, which, on piercing th.s clay, often ascends wit ^"^ J^f™ ?™H,™ 

 workmen have scarcely time to escape. Here the plastic clay seems to be otter the wnductin^ ^edium, 

 or the reservoir of the water yielded by the chalk. Paris .6 known to be situated in a distr whose 

 ™„,£L,«„ ™i.«„«« ,,-,> m „c t i-Wiral with those of London; and therefore we cannot wondei that 



geognostic relations are most identical with those of London ; and therefore »<mfOUerUM 

 there, as well as in many other parts of the north and east of I ranee, Artesian wells ma eve, . « here be 

 sunk ; nor can we doubt of the extension of this very usetul discovery. (Jameson s Phil. Joa,n. for 



'^Hln^wlmust not, however, expect to be able to sink Artesian wells in every description of countr,,™ 

 has been thoughtlessly asserted. On the one hand, the nature of the ground sometimes absouteh pre- 

 vents it, as in granite districts ; and on the other hand, it !s poss.ble that a perforation, if mad.: too ncai 



4 U 



