E. MINERALOGY AND GEOLOGY. 229 



fessor George H. Cook, and others, to whom is to be intrust- 

 ed by the Board of Centennial Commissioners the duty of 

 collecting whatever will best answer the purpose in ques- 

 tion. They have established an office at No. 265 South 

 Fourth Street, Philadelphia, where they propose to bring to- 

 gether the collections, and to make a suitable selection for 

 transfer to the Centennial establishment. Producers and 

 consumers of iron ore and other minerals are invited to call 

 and ascertain the plans and progress of the association. 



DISTRIBUTION OF VOLCANOES. 



Henry Howorth some time ago contributed to Nature an 

 interesting: letter in reference to the distribution of volcanoes 

 on the earth. He adduces abundant evidence namely, the 

 testimony of many Russian and other travelers to show that 

 Humboldt was quite in error in supposing that a region of 

 volcanoes and volcanic action existed in the interior of Asia. 

 Fires, indeed, are found there, produced by the ignition of 

 seams of coal and of streams of carbureted hydrogen gas, but 

 of volcanoes proper there is not a trace, either in the interior 

 of China or in the region of the Himalaya Mountains. With 

 the establishment of this fact disappears the only exception 

 known to the rule that volcanoes, instead of being found 

 chiefly on areas of elevation, are invariably found in areas 

 of depression, or close to the boundary-lines which separate 

 them from the areas of elevation. This general rule seems 

 to be first distinctly established by Howorth's inquiry, the 

 result of which is that all the large land surfaces of the earth 

 the laro-e continental and insular surfaces are more or less 

 in process of gradual or rapid elevation. There are a few 

 small areas of depression on the outskirts and borders of the 

 great land masses, but these are very local and unimportant, 

 and with this slight exception the continents of America, 

 Asia, Europe, Africa, and Australia are all more or less ris- 

 ing. This necessitates a corresponding sinking of the sur- 

 faces covered with water. Evidences of this latter fact are not 

 easy to find, although they exist. Having shown this gen- 

 eralization, the fact becomes still more striking that we shall 

 search in vain among the large areas of upheaval, except 

 along their boundaries and fringes, for any active volcanoes. 

 12 A, 1874, IX., 142. 



