464 



New Mode of forming curved Lines, 



Fig. 76. differs from the above only in this, that the angles 

 are taken outside. Set up three pegs, say 50 links apart, as be- 

 fore, and fix the cross staff in ;•, with one sight on the line r b a. 



and the other point- 

 ing to c. Then 

 measure r b and r c, 

 and remove to the 

 line e c b; draw e d 

 equal to r c, and e c 

 equal to r b, and so 

 on. 



The same end may 

 be obtained by a theo- 

 dolite, or by any other 

 instrument for taking 

 angles ; or even with 

 three needles stuck 

 in a board forming 

 the requisite oblique 

 angle ; setting the in- 

 strument in b, 50 

 links from «, with 

 one leg of the angle 

 on the line b «, and by the other leg directing an assistant to 

 place the peg c at the distance of 50 links. Then remove to c, 

 and soon. 



Having been employed by an architect, some years ago, to 

 carry the pins used in laying out an approach road, I was very 

 much surprised at the unsystematic manner in which it was 

 done ; and the architect being one of great learning and expe- 

 rience, I concluded that there was something wrong in his system. 

 He began at the portico of the house, sticking in a pin at the 

 point which was to be the middle of the walk, and, proceeding in 

 the destined direction onwards by guess, he stuck in another 

 pin at a short distance, and so on to the end of the line. Then 

 returning to the portico, he set up his theodolite, and commenced 

 taking the level, by making an observation at every 100 ft., for 

 the purpose of ascertaining the depth of cutting or banking ne- 



