SOUDAN FORMATION. 245 



of thousands, of dollars have been spent in exploring these narrow bauds 

 without any retiu'ns. 



A close study of the map shows some places which seem favorable for 

 prospecting. In a general survey it is impossible to study a district in such 

 detail as to warrant an expression of opinion as to individual localities. In 

 fact, such very detailed study with a view of determining the exact location 

 of ore deposits can hardly be considered a part of the functions of a 

 national survey. 



The exploration of the iron-bearing formation as an economic problem 

 should be handled by the mining companies. They would unquestionably 

 find it greatly to their advantage to have competent geologists make exceed- 

 ingly detailed surveys of properties in which there are large belts of the 

 iron formation. If such surveys show that certain areas have conditions 

 favorable for ore deposits it would be advisable to burn over such areas 

 so as to increase the number of exposures, and thereby make the areas more 

 accessible. ^ Finally the favorable locations should be narrowed down still 

 more by careful dip and horizontal magnetic-needle observations. Only 

 when ail this preliminary work is done should a decision be made in refer- 

 ence to underground work. 



The cost of such preliminary surveys as are advocated is insignificant 

 when compared with the money required for diamond di'illing and other 

 underground work. Many such expenditm-es in the past would not liave 

 been made had the results of the surveys advocated been available. Apropos 

 of the cost of the •diamond-drill work, it may be stated that, from informa- 

 tion derived from various sources, the estimate has been made that one of 

 the old companies operating in the Vermilion district expended at least 

 Si, 000, 000 in exploratory work without having uncovered thereby any 

 body of ore of size sufiicient to wan-ant its exploitation. The preliminary 

 expenditure of a very small fraction of this amount of money for good sur- 

 veys in advance of underground work would have made unnecessary the 

 expenditure of much of it, and perhaps would have rendered the expenditure 

 of a part fruitful. 



In conclusion, it may be recalled that the only productive inines are at 

 two localities, one on the belt of iron formation near Tower and Soudan, and 

 the other on the belt of iron formation rumaing east from Ely. Notwith- 

 standing extensive but more or less haphazard exploration of other large 



