GEOPHYSICAL LABORATORY. 137 



extensive, as was to be expected. In fact, through the experience 

 gained in this work it proved practicable to carry out a second 

 three-mineral system (lime, alumina, magnesia) similar .to the first 

 within a period of a few months. 



THE SECONDARY SULPHIDE ENRICHMENT OF COPPER ORES. 



Since about the year 1900 the problem of the secondary enrichment 

 of ores has been growing in interest, and certain phases of it have 

 been studied as opportunity offered, both in the laboratory and in the 

 field. In 1911, Professor L. C. Graton, of Harvard University, planned 

 a much more comprehensive study than has been undertaken hitherto, 

 of one particular phase of this problem, namely, the secondary sulphide 

 enrichment of copper ores. He was fortunately able to enlist the inter- 

 est and the cooperation of the copper-mining industries, which secured 

 for him special privileges to examine all the principal copper-sulphide 

 mining districts of North America. 



This fact of itself is of more than passing interest, for although 

 cooperation between science and industry has been much cultivated in 

 other countries, notably in Germany, and without recorded exception 

 has resulted in great advantages to both participants, but little open 

 cooperation of this character has been attempted in the United States. 

 There would seem to be no reason why American science and industry 

 might not enjoy similar benefits where their common interests are 

 involved. 



Recognizing the necessity for laboratory studies on the conditions 

 of formation of the copper-sulphide minerals, the means for identifying 

 them, and the alterations to which they are subject. Professor Graton 

 proposed to this laboratory that such investigations be undertaken 

 here in direct collaboration with those who might be chosen to under- 

 take the systematic field investigation which he proposed to inaugurate. 

 After some consideration of the scope of the plan proposed, which was 

 rather too large for the resources at our disposal for such a purpose, but 

 in full appreciation of the advantages which such cooperation might 

 offer, the invitation was accepted. In fact, at the moment when the 

 invitation was received, laboratory work on the stability of the sul- 

 phides of copper and the relations between them was already in pro- 

 gress, following upon similar work upon the sulphides of iron, of cad- 

 mium, and of mercury, the successful results of which enabled us to 

 proceed with full confidence in the outcome of the larger plan now 

 proposed. 



The difficulty in the matter of resources was happily removed by 

 an allotment from the funds at the disposal of Professor Graton. 



Thus the systematic study of one of the larger problems of geology, 

 a problem of interest equally from the scientific and the economic view- 

 points, was inaugurated early in 1912 under the most favorable condi- 

 tions and has been prosecuted with vigor and success since that time. 



