SHORT NOTES. 209 



or delineated on the sketch in such a manner, with reference to 

 the surrounding objects, that there may be no difficulty in 

 recognizing- it on the published map or on the ground. 



It is essential that the route should be continuous, and that 

 it should close either on itself, or on some point that has been 

 well and independently fixed. 



In closing, the same accuracy of description is required as 

 at starting. 



Information as to the method employed and circum- 

 stances under which the work has been 

 executed to be always furnished. 



(III). — As the compiler has to fit together routes executed 

 by different men under different circumstances, but all alike in 

 the one respect that they have been mapped under conditions 

 precluding absolute accuracy, it is of the greatest importance to 

 him to have the fullest information as to how the work has been 

 done, in order that he may weigh the evidence properly. 



The explorer should, therefore, attach to his map a clear 

 statement as to the following points : — 



1. How he has measured his distances; if he has used a 

 base line, he should indicate the position, and state the 

 length and how it was measured. 



2. How he took his directions ; if a compass was used, what 

 sort of compass it was. 



It would also be an advantage if the traveller would occa- 

 sionally take observations for the variation of the compass. By 

 doing this, he will discover if his bearings are being affected by 

 any local magnetic attraction. 



Should he take such observations, he should state where 

 and how they were taken, and with what result 



3. If he has reason to think that the compass needle may 

 have been deflected by local magnetic attraction during 

 any portion of his route, he should state the limits of 

 such possibly disturbed areas. 



4. He should also give information as to any portions of 



his route that differ from the rest in having been mapped 

 with more or with less care or under more favourable 

 or less favourable circumstances. 



