PLOTTING QUADRANT, LEVEL, AND CALCULATOR. ^£5 



the angles with a protractor; but I have introduced it here, than tlie com- 



1 I - • ' \ ' i_i r 1 • ^i-- n nion method, 



to show that my instrument is capable ot solvmgthis, as well 



as all other cases of obtuse-angled triangles, and might, by 

 extending the arc to a semicircle, as shown by the dotted 

 lines on the figure, solve any triangle. In the practical pro- 

 blems in surveying, which follow, the triangles can always be 

 taken right or obtuse angled, and the instrument as at pre- 

 sent constructed is fully competent. I might here add, that j^jne divided 

 a given line can readily by my instrument be divided into by it into any 

 any number of equal parts; ,drq,wings might be enlarged or parts. 

 diminished, as readily as with the proportional compasses, and 

 many other equally useful purposes may be effected thereby. 



First, — To meamre an inaccessible distance, hy a perpeadicu^ 

 1 27' line set off towards the right hand, /torn the line or base 

 between the obser per a,ria objector. 

 Set the base line of the instrument in a Vine pointing to Method of 



the object, at the same time place a staff at any distance at measunug aa 



, ,.■,,.• , f .1 1 V inaccessible 



pleasure, as a perpepdicplar (being 90 degrees irom the base), distance. 



On this perpendicular measure, any distance (say 50 yards 

 or other measuresj as a second station ; move the instruWent 

 to this distance, and place it with \ts perpend iciilar in the 

 same line as before; the instrument being so pkced, set the 

 lower-limb pointing to the object, and with the screw make 

 the same fast; this done, the distance of the object will be 

 thus readily known. Raise the moving perpendicular of the 

 instrument to the division 50 (as before suggested), then with 

 this height move the same by means of the nul, till the extre^ 

 mity intersects the lower li?nb befove set, at which intersection, 

 the distance from the second station will be shown ; and on 

 the base line will also at the same time be seen the distance 

 from the first station : this is a case of right-angled triangles. 

 ]^ot€, — As the divisions on the perpendicular are denomi- 

 nated (either feet, yards, poles, or other measures), so will 

 the distances be indicated on the oXhex limbs, and on the base 

 of the instruiflient. 



Secondly.--— To determine the distances of any two inaccessible 

 objects, both objects lying in a right line from the observer. 



As before directed, place the instrument with its base in 'j.^ moagtire 



the the distance ctf 



