ciiAf. 111 ACCOUTREMENT FOR THE HELD a* 



geological value, as they can easily be printed on an 

 enlarged scale. The minute details of a natural or 



sal section of rocks can be obtained by photography 

 in a way which no hand-sketch could equal, save with a 

 great expenditure of time and labour. The great defect 

 of a photograph for geological purposes arises from i he- 

 equal prominence assumed by essential and non-essential 



>, insomuch that the geologist himself may hardly 



Anguish them on his prints, especially a few 



days or weeks after he has been to the place. In such 



n stances, it is quite allowable for him to aid his 

 work by marking off the structures on the actual rocks 

 before he begins to photograph them. For example, he 

 will sometimes find that a bucket of water dashed over 

 the section will bring out the points of which he wishes 

 to obtain a faithful record. Suppose that two rocks which 

 he wants to distinguish are so like each other in tone that 

 they will be sure to be merged into one in the photograph. 

 He can sometimes make their boundary-line distinct by 

 here and there rubbing one of them with a stone, so as to 



\e its coating of lichen or weathered crust, or by 

 using a bit of white chalk either to mark a line or to put 

 letters or numbers on the several parts of the section. 



re will soon teach him how to combine clearness 

 and fidelity with due respect to the preservation intact of 

 the geological and artistic features of crag, ravine, sea-cliff, 

 or quarry. 



As every device which saves labour and time in the 



field, or which adds to the clearness of the work, is 



deserving of attention, I would refer here to the use of 



sly-coloured pencils for expressing at once, upon 



