224 PLOTtlNG QUADRANT, LEVEL, AND CALCULATOR. 



t#o inaccessi- the line of the objects; th^n by means of the upper Hmh, set 



"Lie objects in a ^_„, , -. « ii . ,. 



fitlu ikie, ^'^ S^ degrees, place a staft as a perpendicular at any distanct 



at pleasure (say 50 as before)^ This done, remove the in- 

 strument to this second station, and place it so that the 

 upjy4>r limb fstill at 90^) may be in the siime line as when at 

 tbe first station ; this done, iriove the upper limb into the di- 

 rection of the nearest, and the Imver Ihhh into the direction, 

 of the most distant object; which /i/n^.? being so set, and 

 inade fast, the distance of both objects from the second sta-* 

 tion will be seen on the two limbs, and the distance from the 

 first station a:t th^ same time seen on the base line, by setting;, 

 and moving the perpendicular as directed in the last case. 

 This is also a case of right-angled triangles. " 



Thirdly. — To measure an inaccessible distance in an oblique^ 

 angle, where a right angle cannot be obtained, by reason of 

 some impediment on the ground. 



To measure an At tlie first station, from which the distance is required, 



inaccessible p]ace the instrument; then set up a staff in any attainable 



ifHtance in an ^ . i , , ,. 



•Mi^ue angle, direction, to any distance at pleasure (the more distant the 



better). The instrument being set with its base in direction 

 to the staff, with one of the moving limbs take the angle of 

 the object, and with the screw fix it thereto. This done, 

 move the instrument in the direction of its base (being be- 

 tween the first station and staff set up] to any certain distance, 

 (say 50 yards or measures) as a second station. From this 

 secoftd station again take the angle of the object, and theieto 

 fix the other moving limb ; this done, the distance both from 

 first and second station, as also the bases and perpendiculars 

 thereto will thus readily be seen. Set the perpendicular 2cX 

 random to any height, move the same till the upper point 

 intersect the upper limb, or that most distant fiom the base, 

 then read off on the parallel, the divisions parallel to the base 

 subtended between the two hjpothenuscs or limbs; if this 

 distance or division be equal to the distance measured on 

 the base line, {i. e. 50) then the distance of the object from 

 both stations will be shown on the two limbs, as will also tl»e 

 base and perpendicular on the resf>ective lines. If the divi- 

 sions on the parallel (\o not agree with the distance measured, 

 the perpendicular mu^t he altered till that division is shown, 



when 



