EDITORIAL 277 



The total expenditure of the survey for this great series has been 

 less than $150,000. Considering the magnitude of the iron- mining 

 industry, and the intricacy and importance of the geological forma- 

 tions involved, the expenditure is very conservative. Larger sums 

 than this, wq are reliably informed, are spent by single mining com- 

 panies in the Lake Superior region in the exploration of very limited 

 areas ; indeed, it is in a large measure due to the co-operation of such 

 companies that this series of monographs has been prepared within 

 the amount named. 



The work of the survey is highly appreciated in the Lake Superior 

 region, where a good geological and structural map has come to be 

 regarded as an absolute prerequisite to intelligent underground ex- 

 ploration and mining development. The working maxim has been 

 firmly established that before expensive underground exploration is 

 attempted it is economy to spend whatever is necessary — which is 

 usually a comparatively small amount — to ascertain all that can be 

 learned at the surface. A proper geological map of the ore-bearing 

 district saves many thousands of dollars in sub-surface exploration by 

 limiting the areas which it is worth while so to explore. Professor 

 Irving and his colleagues mapped in detail the iron-bearing formation 

 of the Penokee- Gogebic district in the later seventies and early 

 eighties, and up to the present time no ore-bearing areas have been 

 found outside the narrow limits they laid down. While elsewhere, 

 from time to time, exploration has enlarged the boundaries of the ore- 

 bearing formations mapped by the earlier surveys, it is within limits 

 to say that a vast amount of subsurface exploration which might 

 otherwise have been done in barren areas has been localized in 

 more promising fields by means of the geological maps. 



This series of monographs constitutes a valuable contribution 

 to the theory of ore deposition and to the intricate geology of the best 

 known pre- Cambrian formations. Not only have they an intensive 

 value to local mining men and to pre- Cambrian geologists, but they 

 subserve a broader and scarcely a less important function in the dis- 

 semination, through the industrial and scientific world, of information 

 relative to the sources, the extent, and the modes of origin of products 

 which are the dominating factor in the most important metalhc indus- 

 try of America, if not of the world. 



T. C. C. 



