Method of conducting the Canal Surveys* 23 



spaces included by the parallel lines as there were chains in the align- 

 ments, or, if the smallness and number of the objects to be noted ren- 

 dered it necessary to enlarge the scale, double the said number of 

 spaces were taken for the purpose mentioned. 



11. The offsets as Ko, Kn, Dr, and DS, he. for the breadth of 

 the survey, were in every case represented upon the larger or doub- 

 le scale, that is, two spaces or one half of an inch was assumed as 

 equal to one chain. The offsets at the several stations or angles 

 K. D. H. he. in the base line, were represented by continued red 

 lines. The intervening offsets as L w were indicated by the red dot- 

 ted lines. 



* 



12. The distances between the several stations, or the lengths of 

 each separate alignment, were inserted at the ends of the same, with- 

 in the space occupied by the Canal. The same was likewise done 

 with respect to the intervening offsets and all other measurements up- 

 on the base line, the distances being in each case reckoned from the 

 last preceding station. The lengths of the offsets were inserted on the 

 right and left of the Canal, according as they were made on one side or 

 upon the other. 



13. In the field-book thus arranged all lines appertaining to the 

 survey were described as nearly as possible in their true positions ; 

 likewise all such objects of interest of every description, including 

 roads, streams, buildings, -changes in the inclination of the ground, 

 geological characteristics, localities of minerals, he. he. as came 

 within the limits of the field-book, were carefully sketched. The 

 sketches being executed with greater accuracy through the aid of 

 the parallel lines as above described. 



14. The results of the measurements for the several bearings and 



distances were distinctly put down upon the lines to which they res- 

 pectively belonged, and the whole accompanied by such remarks as 

 were necessary completely to elucidate every thing of importance re- 

 lating to the survey.* 



* It is perhaps proper to remark that occasional observations for determining the 

 variation of the magnetic needle were contemplated, but for the want of the neces- 

 sary instruments, were omitted. The importance of such observations was howev- 



• • 



precision 



the magnetic bearings of distant and permanent objects, so that, should suitable ob- 

 servations be hereafter instituted, the exact variation of the magnetic meridran-as it 

 existed at the time of making the survey can be easily ascertained. 



