Meafuremint of a Bafe on Hounflow-Heath. 41- k 



level) were brought to the proper height, the platform was 

 laid upon them ; and on that the ftand itfelf being placed, its 

 pofition was ultimately correded by the fpirit level laid on 

 the top of the table. Each of the beech pickets had a hole 

 bored through its top, fit to receive a piece of flrong tent- 

 line, by which, and the help of one of the camp mallets, the 

 pickets were eafily pulled up again, when the platform w^s to. 

 be removed to a new fituation. 



Boning Tetejhope and Rods, Tab. XVIIL 



In order to trace the line of 200 yards or 6co feet through 

 the air, fmm one fixed ftand to the other, it was ufual, in the 

 iirft place, to flretch a cord extremely tight along the ground, 

 and to divide the fpace into rod lengths, by fmall wooden pii>s 

 placed clofe by the cord, which remained there, and accordingly 

 marked, very nearly, the points over which the centers of the 

 intermediate flands were to come. A piece of wood, abouf 

 fourteen inches in length, and one and a half in breadth,, 

 painted white, with a narrow black line along the middle of 

 it, being prepared for the purpofe, was laid on the furface of 

 ^e farther ftand. The boning telefcope, fourteen. inches long, 

 and one and a half in diameter, with, a fmall magnifying, 

 ■power, and moveable obje6l-glafs,' fo as to fit it for very fhort 

 diftances, was th6n laid on the furface of the nearefl: ftand ;. 

 which, by means of wedges placed under the legs, had that 

 ■'fide towards the farther ftand fo elevated or deprefiedy. as to ■ 

 bring the crofs v/ires to- coincide- with the black line on the 

 painted board. Twenty- four boning rods had been originally 

 provided ; but it rarely happened, that more than eight or tern 



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