228 PHOTOGRAPHY IN GEOLOGICAL SURVEYS, 



may be mounted upon the same sheet with it, every photograph 

 being distinguished by a sign. The position from which each view 

 was taken should then be plotted accurately on the plan, and the 

 direction in which the camera was pointed indicated, as should also 

 be the focal length of the lens with which the view^ was taken, and 

 in the field should be included one or more graduated staffs, so as 

 to convey an impression of the scale of the objects photographed, 

 and the correct position of each of these should also be indicated 

 upon the plan. The value of these detail points will be greatly 

 enhanced if they are sent to the geological surveyor to be colored 

 while the objects are before his eyes. The classification of the 

 collections calls for no special mention, as they would be arranged 

 in such a manner as is most convenient for office work in each 

 colony. The whole of the negatives should be preserved as records, 

 and before any permanent prints are obtained a full size trans- 

 parency should be made from each, so that any negative may be 

 duplicated shoidd any accident befall it. "Retouching" or 

 " improving " of negatives should not be allowed under any 

 circumstances. 



