181 



Proceed as before. Divide 190,000 by 

 the length of A B which we will suppose is 

 5 chains (500 links). 190,000 -=- 500 = S'SO 

 chains (3 chains 80 links). Measure off 

 along A D and B C a distance of 3.80 

 chains and put in pegs as before in the 

 field. 



The point to be borne in mind in this 

 kind of work is that the area must be 

 worked out on the plan before any pegging 

 out of measurements in the field. 



Before closing this short article it may 

 be worth while considering the measure- 

 ment of an area which it is impossible to 

 see across on account of fruit trees or 

 other obstruction to sight. Take as an 

 example the orchard, Fig. 6 



N 



N N 



N 



exact point in line by aid of the cross staff 

 and put in a pole at this point. Now pro- 

 ceed to chain from A to this intermediate 

 point and then on to B and lay out the 

 figure in triangles as before explained. 



Should this method fail nothing is left 

 but to measure round the area as follows. 

 Measure from A to D, and take the bear- 

 ing of the line with a compass, then from 

 D to B, B to C, C to A, taking the bearing 

 in each case. (See Fig. 5.) 



Now draw on paper a line N S to indi- 

 cate the direction of North. Draw A D to 

 scale from a point midway in this line 

 bearing the number of degrees ascertained 

 for it by the compass (say 120 deg.). Draw 

 parallel to N S i another line N S 2 and 

 from the point D draw DB to scale bearing 

 the number of degrees ascertained for it 

 by the compass (say 80 deg.). 



It is impossible to see from pole A to 

 pole B on account of the trees. Try first, 

 if it is possible to see both poles from an 

 intermediate point between them in the 

 middle of the orchard. It is of ten the case, 

 when one cannot see from one point to the 

 other, that both poles are visible from a 

 middle point. If this is so then find the 



Proceed with the remaining lines as 

 described, and the proof of correct read- 

 ing of the angles lies in the fact that C A 

 will close on the point A. This rarely 

 occurs exactly, an adjustment is then 

 made. 



Full explanations and various cases are 

 given in the writer's book on " Land Sur- 

 veying and Building Construction," by 

 A. H. Haines and A. F. Hood Daniel, 

 published by Messrs. Longmans. 



