„————

75 file lifferent Altitudes: 163

Thus if che Thred P R ſhould cut off Q in the equal limb, 58) de-grecs, che ſame counted the other way fröm 8 to T in che equal limb,and the Thred laid therete would give 667 in che meaſuring Scale.Then FG being 88 3 feet and GH( ſuppoſe) five feet, F H muſt befeet for the Diſtance H K. i

IV. To fad part of 4 Diſtaube.

E che Diſtance of K trom Z were required. Firſt, find H K, then

HZ, by che third precedent: their Difference is K Z. If K Z were

2 Trench, you might from the Tower F, find the bredth of it without

any approach unto it.

V. 7 254 4 Height at tuo Olſervations.

F F H were to be mealured, and che way from E to H were unpaſſable,1 ſo that the Diſtance of E from H could not be meaſured. Voumuſt in chis cafe make two Obſervations. For which purpoſe, take

your firſt ſtation at E, and direct the lights D, A, to the point P: no-

ting what parts the Thred cuts upon the equal limb from Cto B. Thengo backwards in a right line, to a competent Diſtance, as to M; andthere making a ſecond ſtation, obſerve(as before) what degrees the Thredcuts upon the equal limb from N to O:(the two fights L. Is being juſt-1

1 5 the contrary ſide of the Quadrant, famely from D to V, andfrom L to* and applying the Ihred thereto, look What parts it cutsfrom the meaſuring Scale at V and V. Take the leſſer number of parts

out of che greater, noting the Difference. Meaſure alſo the Diſtance of

your two ſtations, namely, from E to M, and add three ciphers to thatmeaſure; This laſt number muſt(in this kind of work) be divided al-ways by the fore · noted Difference: and the Quotient will give the Alti-tude of F aboye G.. i

.„ nne, 25Let the firſt Obſervation cut c 38 5 ger. in che equal Iinb. The

ſecond 56 5 Cr. Count che firſt Ark from D to Y: che Thred chere

laid gives 1 250 in the meaſuring Scale. The fecond ſo counted from

L to V, gives 667: The Difference of cheſe two is 583. Let the Di-f N 2 n 5

*

932 feer. This multiplied into 667, makes 62364 flom whencecutting away the chree right hand figures, chere remains 62.364 or 62

directed to the point F.) Then count theſe two Arks in the equal limb

ſtance