GEOPHYSICAL LABORATORY. 165 



best opportunity now existing for the study of this particular form of 

 subordinate volcanic disturbance. 



Through the courtesy of the National Geographic Society, the Geo- 

 physical Laboratory was permitted to send three members of its 

 own staff to make studies of the chemistry and physics of the fumarole 

 region and of the general geologic relations in so much of the region 

 surrounding the volcano as might be covered in one short Arctic 

 summer. This amounted altogether to a Uttle more than two months. 

 Every courtesy was shown by the Society and every facility given 

 which the rather strenuous conditions of life in so remote and so deso- 

 late a region permitted. 



Many of the fumarole temperatures were measured. It proved 

 possible to collect samples of the gas from some, as well as quantities 

 of incrusted salts. On account of the rather overwhelming amount of 

 rain in this region in the summer season, favorable conditions for the 

 accumulation of water-soluble salts seldom occur, but in general the 

 efforts to obtain characteristic material were fairly successful. It 

 also proved practicable to visit Katmai crater, to make a study of the 

 characteristics of the eruption as revealed in the deposits of ejected 

 material, and to obtain extensive collections of the sohd ejecta for 

 laboratory study. 



It may be said that by far the largest portion of the gaseous matter 

 emanating from the fumaroles at the time of this visit was water- vapor. 

 Little evidence was found of the presence of explosive gases such as 

 commonly characterize the violent stage of an explosive volcano, 

 though chemically active gases (H2S, HCl, HF) are still present in the 

 fumaroles in small quantity. One must not be overhasty, however, 

 in adopting the simple assumption that the great field of fumaroles is 

 merely the result of a heavy deposit of hot ash or other ejectamenta, 

 accumulated in an extensive drainage basin and gradually cooHng 

 there. To the experienced eye of the geologist the location of the 

 fumaroles, remote a,nd apparently quite separated from the center of 

 activity, together with the character of the deposit through which the 

 gases have emerged, plainly indicates that this is not a simple case of 

 cooling of a great mass of debris kept more or less continuously sat- 

 urated by atmospheric precipitation. Moreover, a number of the 

 fumaroles are found on the hillsides above the valley and have no 

 present relation with the deposit of debris. That such a mass, amount- 

 ing in all to something like a cubic mile, should find its way from the 

 main vent to a single distant valley without invading neighboring 

 or intervening territory is in fact quite unthinkable. 



From observation nothing is directly known either of the time 

 (save only that it is overlaid by the ash) or the manner in which 

 this deposit was laid down, but it is certainly true that new mat- 

 ter, to the depth of 100 feet or more in places, has appeared in 



