VADOSE ORE DEPOSITION 
275 
CLIMATIC INFLUENCES IN VADOSE ORE 
DEPOSITION 
By Charles Keyks 
The desert, which according to Sir John Murray, occupies more 
than one-fifth of the land surface of the globe, and which, as we 
now know, profoundly affects another one-fifth, appears to be 
peculiarly the home of the metals. Iron alone is possibly an 
exception. Concerning changes with depth the ores of arid 
regions present many features which are altogether unknown in 
those lands with which most of us are most familiar. One aspect 
of the far-reaching influence which depth has on the character of 
ore deposits is of as great practical importance as it is of scientific 
interest; yet it is a feature which is quite generally overlooked. 
It is to this phase of the depth-factor that attention is here mainly 
directed. 
Since we no longer can regard all ore-bodies as having been 
formed directly from igneous emanations arising from the depths 
we have to recognize the fact that there are really two great 
primary classes of ore deposits economically equally important. 
- Those belonging to the class of deep-seated origin we shall have to 
pass over at this time with the mere mention of their existence. 
The other grand/ group, the one with which we shall have here 
particularly to deal, finds meager representation in humid coun¬ 
tries where modern mining began. Its wide expansion in arid 
lands is such as to make it often the only class of ores over large 
tracts which is encountered or mined. Once thoroughly under¬ 
stood in regions of excessively dry climate the special features 
become easily recognizable also in other lands. 
Certain of the broader aspects of the subject, as especially 
displayed in a humid climate, I have already considered in a paper 
