28 S. F. EMMONS — THEORIES OF ORE DEPOSITION 



in the formation of ore deposits of waters of meteoric or of igneous 

 origin has more recently received a further impulse in the discussions 

 provoked by the presentation of proposed genetic classifications of ore 

 deposits by W. H. Weed and J. E. Spurr. These geologists took an even 

 more advanced position than Vogt in regard to the direct influence of 

 igneous agencies in the formation of ore deposits, adding siliceous segre- 

 gations to his class of magmatic differentiation products and very greatly 

 enlarging the scope of his pneumatolytic class. ' The influence of these 

 new views is already seen in the current literature on ore deposits, espe- 

 cially in articles where the author, though not in possession of full data, 

 still feels it incumbent upon him to present some tentative hypothesis of 

 origin for the deposits which he is describing. 



Results achieved 



The wide divergence of views shown by these discussions to be held 

 by recognized authorities on the subject might lead one to conclude that 

 we are as far as ever from a universal agreement on accepted theories. 

 A more deliberate consideration of the progress of investigation and 

 verification during this last period, which has been but too briefly and 

 imperfectly set forth in the preceding pages, will show, however, that 

 the advance in this direction has been real and permanent as far as re- 

 gards the later stages of ore formation, which are more susceptible of 

 actual proof, and that the disagreement lies rather with the ultimate or 

 more theoretical sources of derivation, which must always remain to 

 some extent matters of opinion. 



Bibliography 



It being considered unadvisable to print a full list of works consulted 

 during the preparation of the preceding paper, titles of those only that 

 contain important bibliographies on ore deposition are appended. 



A. G. Werner: " Neue Theorie von der Entstehungder Gange." Freiberg, 1791. 

 J. Waldauf v. Waldenstein: " Die besonderen Lagerstatten der nutzbaren Min- 



eralien." Wien, 1824. 

 K. A. Kuhn: " Handbuch der Geognosie," IT e band. Freiberg, 1836. 



B. v. Cotta u. H. Muller: " Gangstudien," I te band. Freiberg, 1850. 

 Johann Grimm: "Die Lagerstatten der nutzbaren Mineralien." Prag, 1869. 

 Gonzalo y Tarin : " Memorias de la Com te del Mapa Geol. de Espana." Madrid, 



1888. Tom. II, pp. 73-181. 

 E. Fuchs et L. DeLaunay : " Traite desgites mineraux et metalliferes." I. Paris, 



1893. 

 K. A. v. Zittbll: " History of geology and paleontology." Translation by Mrs. 



Ogilvie-Gordon. London, 1901. 

 Richard Beck: " Lehre von den Erzlagerstatten." Berlin, 1901. 2d ed., 1903. 



