LEVELLING.

Grey River Argus, Issue 73, 30 June 1866, Page 3

LEVELLING.

'•;iifcsv. : The following remarks, . frqp a lecture delivered before the Royal Ife^ricultural College (England) by Mr Wallace Fyfe, may be useful to our miners in making ditches and flumes* for the conveyance of water, as well as to our farmers in draining land: — . Fortunately water will flow on the very Blieptest incline, and there are very few sigStions in which a suitable outfall is lwpFound, if only of 2 inches in 100 yards -^HS ** ia * * v au^* °* better will suffice. J or declination is so small that I infjSKagriculturists, although possessed f of ffilMaent outfall, are often found harboring^gb mistake that drainage is^pr them a uugg impt sable, when it is nothing of tH^rt. The eye, too, is often deceptive in regard to the ground level; and the use of iiSitruments alone can der,. termine the true s^te of the case. „ V Levelling is the easiest and most elei| * mentary task in surveying ; yet it is onfe '& requiring the utmost nicety and attention. Hi Various kinds of levels are constantly ||l. ~ employed 'in setting-off or finding the |||H levels for drains. JBut' in order to test the-fall, cut the drain accurately ahd unij^plforihlv before laying in the tiles aj&pther w- ; materials ; three stave 3, two -^Hqual jM||:length, about two feet, and oi^Ksuit : 'W" itself in the drain to the height y^ : - laying at one end cross piecd^^Hrood ;%l' nine inches in length, are coi^^^V em- :--,."' ployed-Avhore the gi'ound^^^Hrably uf^^ha^&nd. answer well whe|^^^Kunis though not wh^^^^Rurved. - W : . The drain being first cu^HK proper as far as the eye^Vjudge, one staff is held perpena§mlarly on the %£*? ground at the upper end, ahd another at 3£|| the lower end of the drain, whilst the p^| other staff, adjusted to stand at thecorW& rect height of the other two above the I drain bottom, is moved along from one Cad to the other j the surveyor at one end of the drain bringing his eye down into the line with the upper edge of the cross-heads on the staves, notices whether or. not that of the long staff keeps the high line. According as in moving it along he perceives it r?pe above or sink below this line, the bottom of the drain must be altered so as^to make the three cross-heads coincide. " Care must, how-' ever, be taken to ascertain that the bottom does slope in the right direction, as these staves only test its regularity, not its inW g ; clination. Staves painted in strong con;%!s?l> traat of colors, .are the most readily dis;*||jL. tinguishable. " ; I ;^he mason's plumb-level forms a very 'I'M iM»venient instrument for the use of ?^ l^iiners. By "making a mark as far off M he plumb Une as will subtend an angle M to the intended fall of the drain, 'M ffl 10 l e y e^ er can always keep to the angle fim i the Inclination of the fall, Thomson's iffl Vorkmari's Level is an instrument cal- « v^^lated to enable drains to be carried out. "^pa a uniform slope. It differs only from. '■J^jstifor mason's plumb-level in having the; • : ;;. ; v-|^mghts capable *of being lengthened or ; ]3i|M|itened by shifting the hypothenuse, so yKYjfl&i it will forai any required angle with r^p " : .:tlie base. There is an index head, on :# K^tiich the rate of slope is indicated on a f "graduated scale, and the instrument is * '''""* kept at any given point by tightening a nut at the index head. The instrument ;i^i»nd all tile workman lias to do is to see .V^^jfhat the plumb line strikes the centre. •i ! ■ patent inclinometer carries out !tne same principle by it from a triangle to a full parallelogram. In fact, when I first saw them applying it in levelling the drains on the estate of Torbarie jPiJI, I really thought the machine^ was icpmposed of the four spars of a common feeld gate, with a diagonal moving, ■upon |iiiis; which made the bottom spar down in the drain parallel wreh the top spar Been above it, when^set to the required inclination. I thought the instrument very effective, but ridiculously simple. But by the time it passed through the hands of Patent Office, and I was called upon by the inventor to write the accompanying descriptive pamphlet which is - ; : : jssued ,with it by the makers, I found.it :> r^r: had become quite complicated since I first : SS«aw if in its field-gate form; the top ;^^parallel necessarily represented to the eye fraptihe amount and direction of the slope, 'but now jan a^Htional limb or parallel ■i was hinged at Oiie end to the top bar, and * from th» other end depended a plummet. v\ In. action the moveable limb had to be raised from its parallel position to one Mfivperfectly- horizontal, as indicated by the and thus marked the rate of an index spirit level,- which is in a japanned frame with brass. .^Wtfiated arch, and mounted on a tripod ; ■;■:» : 'v^^-with levelling screws to bring it p' To this is adapted an i; yme carrying two sights with cross f&f Vy/y*^ 6 turning round on a Ife f /A 0 * cm 8 raised or lowered at w$ x : ■ \l/ Therate of rise or fall is ascer|p. {inspection. By levelling and \the instrument in the plane of <^Hk mit will also indicate the moßt J^a^^^eJfall. The cost, with tripod : £i ißs. ■■•*■,■■• ■■■■■.-.■ "Dumpy" level is more popu- '■!:■ Jila^amongst surveyors, but it is princi- ' -ll^lly employed where the levels, require .si|if^h:be continued for miles, and the height ■-'.'ipiSf one point above another determined to Vji'^n inch, as in the case of railways. ':■■ This I *$\ level would*be found useful where it became "necessary to conduct water from j » spring head to a considerable distance. All that the surveyor would have to do ! would be to detenniae^^^esJjb^lM^lJ ofthe^^p^ad was above that of the i jpS^fr^^hich the water had to be aban- - **^loiied, for if higher the water would assuredly find its way in pipes, however rugged the intervening surface, care being always taken to guard at any point against too abrupt a t fall, since the water might ptherwise^jlgh in too rapid a current ; and jdrfH^H^etter^fchat the pipes should beJfl^BßParly to the level or even ,iffl|BH[^HHp' as- to produce the same - <^^^^HHH|Kbeing sometimes directed '"^|fe]^ffl[^H^Pp warclß before approaching '^^B^^' discharge to restrain the p^^y^?^M?ff^ — —^"^— — — ■■■■■^ ■