CiiAi’. VIIT.

GEOMETRY.

837

mr /)

Fig. 1067.

H

when the intersection of the several lines drawn from the second centre, with those drawnfrom the first, marks on the paper the position of A and 13.

To measure the Bends of Hirers, as that ofABC: plant at pleasure the two piquets H andI, and measure the distance between them, as200 feet: draw on the plane table the stationline KL, which divide into 200 equal parts, toserve as a scale and to answer to the 200 feetfrom II to I : place the plane table mounted on

its stand at the piquet I, and its point L above w ^ i i

the piquet I in such a manner that it shall betowards the river, and its line LK on the lineIII between the stations: then place the ruleagainst the pin L, and bone the point A by therule, and draw on the plane table along the sideof the rule the line L M> which as well as theothers must have its name written against it ;keep the rule against the pin and turn it towardsthe point B, and draw along the rule on theplane table L N, and continue in succession toturn the rule towards the point C, and drawon the plane table a line L G, and this incontinuation for the sinuosities D, E, F, &c.where piquets must be previously planted, ifthere were not some objects fixed which wouldanswer the purpose : then taking the plane tablefrom the station I, place it at the piquet II,disposing it in such a manner that when boning

by the two pins K, L, the piquet I can be discovered, and place the rule against the pin K,and bone the point A, drawing along the rule on the plane table a line K P, and do thesame with the line K Q, K R, and so on for the other sinuosities, D E F, where piquets alsomust be planted : in this manner all the windings of a sea coast can be traced, by takingup two stations in a boat securely moored or anchored.

To take the Plan of anyPlace where entrance can heobtained , as that of the citadelABCDEFGHI: the anglesbeing distinguishable, plantabout the middle of the plot twopiquets K and L, at any distanceapart, but in such a manner thatall the angles from both piquetscan be discovered : then drawabout the middle of the planetable a station line M N, about athird of its length, which musthave two pins at its two ex-tremities : move the planetable on its stand at the piquetK, so that the station point Mon the plane table comes ex-actly above the piquet K, andbone along the two pins, M, N,till the piquet L is seen in thesame visual ray : place the ruleagainst the pin M, and bonefrom it the angles at A, B, C, D,

&c„ and draw from the pin Fig. 1058.

M, along the rule, the lines

M O, M P, M Q, M R, M S, M T, M V, M X, and M Y : then remove the plane table to thestation L, and place it in such a manner that the point N on the station line shall be abovethe piquet L, and that when boning along the station line, M N, the piquet K can be dis-covered in the same visual ray : then place the rule against the pin X, to bone from this pinall the angles at A, B, C,D, &c. to be taken, and draw on the table the lines 1, 2, 3, 4, &c.,remarking where these last lines cut the former, in order to draw lines through these pointsof intersection, which shall form a figure similar to ABCDEFGHI. A scale may

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