Page:Cyclopaedia, Chambers - Volume 2.djvu/445

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The Method of Plotting, where the Angles are taken by the Theodolite, i. e. by Back-fight and Fare-fight, (as 'tis call'd, fee Backsioht, &c.) is fomewhat different.— To prepare the Angles for plotting, the Quantity of each muff firft be found ', by fubtrafling the Degrees of the Forefight and Back- fight from each other : The Remainder is the Angle to be protrafted. See Theodolite.

The Ufe of parallel Lines is here excluded, and inftead of laying the Protraflor conftantly on, or parallel to, Meridi- ans; its Direction is varied at every Angle. The Praftice

is thus : Suppofe the former Indofure to have been furvey'd with the Theodolite, after the manner of Backlight and Forefight ; and fuppofe the Quantity of each Angle to be found by Subtraction. An indefinite Line is drawn at ran- dom as A K Fig. 21 ', and on this the meafured Diftance, e.gr. 8 Chains, 22 Links, fetoff, as in the former Example If now the Quantity of the Angle A have been found 140° ; the Diameter of the Protraflor is to belaid on the Line A K, with the Center over A, and againft the Number of Degrees, viz.. 140, a Mark made, an indeterminate dry Line drawn thro' it, and the Diftance of the Line A B laid down from the Scale thereupon.

Thus we gain the Point B; upon which laying the Cen- ter of the Protraflor, the Diameter, along the Line A B ; the Angle B is protrafted, by making a Mark againft its Number of Degrees, drawing a dry Line and fetting off the Diftance BC as before.

Then proceed to C ; laying the Diameter of the Protra- flor on B C, the Center on C protracts the Angle C, and draw the Line C D : Thus proceeding, orderly, to all the Angles and Sides, you'll have the Plot of the whole Indo- fure ABC, &c. as before.

Plotting Scale, a Mathematical Inftrument ufually of Wood, fometimes of Brafs, or other Matter ; and either a Foot, or half a Foot long. See Scale.

It is denominated from its Ufe in plotting of Grounds, &c. See Plotting.

On one fide of the Inftrument (reprefented Tab. Survey- ing, Fig. 32.) are feven feveral Scales, or Lines, divided

into equal Parts. The firft Divifion of the firft Scale is

fubdivided into ten equal Parts, to which is prefix'd the Num- ber to, fignifying that 10 of thofe Subdivifions make an Inch ; or that the Divifions of that Scale are Decimals of Inches.

The firft Divifion of the fecond Scale is likewife fubdivi- ded into ro, to which is prefix'd the Number 16, denoting that 16 of thofe Subdivifions make an Inch.— The firft Divi- fion of the third Scale is fubdivided in like manner into 10,

to which are prefix'd the Number 20- To that of

the fourth Scale is prefix'd the Number 24; to that of the fifth 32; that of the fixth 40; that of the feventh 48; denoting the Number of Subdivifions equal to an Inch, in each, refpeflively.

The two laft Scales are broke off before the end, to give room for two Lines of Chords mark'd by the Letters cc. See Chord.

On the back fide of the Inftrument is a Diagonal Scale, the firft of whofe Divifions, which is an Inch long if the Scale be a Foot, and half an Inch, if half a Foot, is fubdi- vided, diagonally, into 100 equal Parts At the other

end of the Scale is another Diagonal Subdivifion, of half the length of the former, into the fame Number of Parts, viz.. 100. See Diagonal.

Next the Scales, is a Line divided into hundredth Parts of a Foot, number'd 10, 20, 30, &c. and a Line of Inches fub- divided into tenth Parts mark'd 1, 2, 3, &c.

Vfe «/ttePiomNG Scale.

I. Any Diftance being meafured with the Chain, to lay it

down on Paper. Suppofe the Diftance to be 6 Chains 50

Links. Draw an indefinite Line; fet one foot of the Com- paffes at Figure 6 on the Scale, e.g. the Scale of 20 in an Inch, and extend the other to 5 of the Subdivifions, for the 50 Links: This Diftance being transferr'd to the Line, will exhibit the 6 Chains, 50 Links, required.

If 'tis defired to have 6 Chains 50 Links take up more or lefs Space, take 'em off from a greater or leffer Scale, i. e. from a Scale that has more or fewer Divifions in an Inch.

To find the Chains and Links contain d in a right Line, e. gr. that juft drawn, according to any Scale, e. gr. that of 20 in an Inch.— Take the Length of the Line in the Compaffes; und applying it to the given Scale, you'll find it extend from the Number 6 of the great Divifions, to 5 of the fmall ones : hence the given Line contains 6 Chains 50 Links.

PLOUGH, or Plow, in Agriculture, a popular Ma- chine for the breaking up of Ground ; confuting of a Train or Carriage, with two large Irons; the one pointed the o- theredg'd; ferving to cut and open the Ground, and draw Furrows therein. See Agriculture, Ploughing. &c. . *

The Parts of the Plough are, the Plough-Beam, th.5

Handle, Tail, Stilts, Hales or Staves, Neck or Share-Beam Earth-board, Mould-board, Breafi- board, Furrow-board, Shield- board, &c. The Sheath, Share-Iron, Coulter, Plough-Pin and Collar-Links, Plough-Pillow and Bolfter, and fometimes Wheels.

The Structure and Contrivance of the Plough is various in various Kinds of Grounds : A particular Delcriprion of all would be endlefs.— The moft ufual are

1° The double wheel' d Plough ufed throughout Hertford^

Jliire, &c. This is apparently one of the bed, ftrongeft,

and of eafieft Draught, of any ; and fuits all kinds of Lands except miry Clays in Winter ; which are apt to clog the Wheels, which are about 18 or 20 Inches high, and the Furrow-Wheel fometimes larger than the other.

2° The Lincolnfiiirc Plough is lingular in its Shape, and very good for Marfh or Fenny Lands, fubjeft to Weeds and Sedges, but free from Stones; by reafon of its Coulter and the Largenefs of its Share, which is often a Foot broad and very fharp.

3° The Suffix fingle Wheel Plough is of a clumfy Make, very wide in the Breach ; fo that the Draught of it ruuft be very hard It is chiefly remarkable for its Shape.

4 Q The Caxton or Trenching Plough, invented to cut Drains about Caxton in Cambridgelljire, in ftiff miry Clay-Grounds.

It is larger than ordinary, and has two Coulters one

before the other ; which bending inwards cut each Side of the Trench — The Mould-board is three times the ufual Length, to caft the Turf a great way off from the Trench.

It cuts a Trench a Foot wide at bottom, a Foot and half at top, and a Foot deep ; and is drawn with twenty Horfes.

5° The Dray-Plough is the moft common. It is made

without either Wheel or Foot; of an eafy Draught; belt in Winter, for miry Clays, where the Land is foft.

6° The Spanijh Plough varies much in its make from our common Ploughs. 'Tis a kind of Semicircle, pitch'd on one End, with the convex Side turn'd to the Plowman, and the concave Side (a little inclined) to the Horfe. Its Tail is in a right Line with the Share.

With this Plough and one Horfe the Spaniards plough two or three Acres of their light Ground in a Day.

7° The Colchefler Plough is a fine light Wheel Plough, with which two Horfes will cut up two Acres of their light Land

in a Day. It is peculiar for its Iron Earth-board made

rounding, which turns the Turf better than any other Plough yet invented.

8° One Wheel Plough may be ufed in almoft any kind of Ground ', being lighter and nimbler than other Wheel- Ploughs.

9° The Double Plough. In this, there is one Plough fix'd to the fide of another ; fo that by means of four Horfes and two Men a double Furrow is plough'd, the one by the fide of the other.

10° Add to thefe another kind of Double Plough, where- by two Furrows are plough'd at once, one under another, by which the Earth is ftirr'd up 12 or 14 Inches Depth, which is of great Benefit.

Plough, among Bookbinders, is a Tool wherewith they cut the Leaves of Books fmooth. See i?«('-BiNDiNG. ■ Piooo n-Monday, the next Monday after Twelfth-day, when the Plough-men in the North Country draw a Plough from Door to Door, and beg Plough-Money to drink.

P l o u o h 1 N g, one of the principal Operations in Agri- culture, perform'd with the Plough. See Plough.

Ploughing is principally either that of Layes, or of Fal- lows. Ploughing of Layes is the firft cutting up of Grafs- Ground for Corn ; which is ufually done in January, when the Earth is wet and the Turf tough, fo as to hold turning without breaking ; in which the Perfection of this kind of ploughing confifts.

Ploughing of Fallows, call'd alfo fallowing, is a Preparing of Land by ploughing, long before it be plough d for Seed. — This is a confiderable Benefit to Lands, few of which will bear above two Crops fucceffively without fuch Refpite. Hence Landlords ufe to bind their Tenants to it once in J Years.

When this is done twice, 'tis call'd twifalloaing, when thrice trifallowing, &c.

The firft is as foon as the Husbandman has done fowing his Corn ; and this is to be very fhallow, well turn'd, and clapp'd clofe together. — The fecond is in June ; when they go the full Depth. — The third, about the beginning of Au- gull — If it rife full of Clods they harrow it down ; but foon ftrick Siz.e, or plough it up again into Ridges.

In StaffordfiAre, befide the three Summer Fallowings, the/ iifually give their Land a Winter fallowing. Pliny com- mends the ploughing of Lands four times ; and fo does fir; gil:

Ilia demum feges votis refpottdet avari Agricolt bis fua foltm, bis frigora fenfit.

Georg. lib. ll

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