210 SHORT NOTES. 



Use of published maps by explorers. 



( IV.) — It is not uncommon for explorers to take a published 

 map and to fill in from their own observations portions of it that 

 have been left blank or that have been incorrectly shown. 



In such a case the explorer should state clearly what map 

 has been used, and what points on it have been assumed to be 

 correct. 



As it is the compiler's business to study the evolution of 

 maps, he may possibly know that some or all of these points are 

 not so well fixed as the explorer supposes, or he may afterwards 

 receive information of undoubted value, which alters the positions 

 assigned to some of them. 



In view of such a contingency, it is very necessary that the 

 explorer should state whether his work fitted correctly into the 

 points as shown in the map used or not. If it did not fit, and if 

 he has altered it to make it fit, he should state what alterations 

 he has made, and how the route would have worked out if it had 

 not been altered. Cases have been known where explorers have 

 distorted their really accurate work, under the impression that 

 they were improving- it. 



Where, on the other hand, the explorer finds reason to alter 

 hitherto accepted ideas as to the configuration of the ground, 

 he should state clearly that he considers his delineation more 

 nearly correct than the old version. 



Where he is at all doubtful as to the truth, but inclined to 

 prefer his own work, he should explain how he would adjust it 

 to the old, should adjustment prove necessary. 



Astronomical observations. 



(V.) — The places where astronomical observations are taken 

 should be carefully marked on the sketch, and a description 

 should be given sufficiently detailed to enable any subsequent 

 visitor to identify the spot within very narrow limits. 



It is not uncommon to see observations for latitude taken 

 over and over again with the greatest possible industry, so as to 

 obtain a value within very few hundred feet of the truth, while 

 the place of observation is described so loosely, with regard to 

 surrounding objects, that the door is opened to an error to be 

 measured in miles. These remarks apply particularly to cases 



