162 Jag (jar— Yolcanologic Investigations at Kilaiiea. 



Introduction : Magmatic Gases. 



The immediate work of the Hawaiian Yolcaiio Observatory 

 since it was established in 1912 has been concerned with i^ecord- 

 ing rather than theorizing. Confirmation or refutation of 

 existing theories is greatly dependent on a knowledge of habits 

 and of the sequence of changes which happen in the course of 

 time and the comparison of charts showing these sequences, 

 with other charts that show such changes as those of rainfall 

 or numbers of earthquakes, or the tides or movements of the 

 sun and moon. It is by comparison of time changes that such 

 great sciences as astronomy and meteorology have been built 

 up. Volcano science has had no such records and our observa- 

 tory is trying to supply the defect. 



Fortunately, however, five colleagues who have worked at 

 Kilanea have written important articles suggesting theoretical 

 possibilities concerning the mechanism and chemistry of the 

 gases and the lava. Three of these papers deal with the 

 ancient problem of water vapor as a cause of volcanic activity. 

 Dr. Albert Brun* of Geneva believes that water is unessential, 

 Professor Dalyf of Harvard and Mr. F. A. PerretJ of Kaples 

 believe that gases rising from heated magma in the depths are 

 the main heating and liquefying agents in liquid lava, without 

 being prejudiced as to the amount or origin of the hydrogen 

 and oxygen which undoubtedly exist among these gases. Drs. 

 Day and Shepherd, § of the Carnegie Institution, after chemical 

 work at Kilauea for two seasons, published results showing 

 that steam certainly exists in the gases blown out from flaming 

 cones on the Halemaumau floor, but the proportion by volume 

 of water among the gases collected was only about four per 

 cent, while the dominant ingredients were sulphurous acid, 



*L'Exlialaisoii volcanique, Paris, 1911. 



f Proc. Amer. Acad. Arts and Sci., xlvii, No. 3, 1911. 



X This Journal, vols, xxxv-xxxvi, 1913. 



§BulL Geol. Soc. Amer., vol. xxiv, pp. 573-606, 1913. 



Explanation of Plate I (fig. 1) frontispiece. — General views, interior of 

 Halemaumau, the lava pit of Kilauea volcano, (a, upper view) Aug. 26. 1915, 9 

 A.M. Upper surface duplex lava column, Halemaumau pit, from S.W. rim. 

 Diameters 780 by 730 ft. (238 by 222 m.). Length liquid lake 700 ft. (213 m.), 

 maximum width of same 220 ft. (67 m.), and depression of lake 410 ft. 

 (125 m.). Bench clinging to wall left 18 ft. (5 m.) and general floor level 

 6 ft. (1"8 m.) above lake. The clinging bench marks lava level of 1914, 

 mossy appearance due to mat of Pele's hair. Western conduit pond on left, 

 sinkhole niches middle and right. Streaming left to right ; minimum incan- 

 descence, fountaining and fuming left ; maximum right. Eising activitj^, 

 crags of bench magma crust tilted and fissured on the right by weight of 

 overflows shown. Panchromatic jDhoto by Jaggsr, camera inclined forward. 



(6, lower view) Jan. 31, 1917, 5 p. m. Depression 45 ft. (13 m.). Diam- 

 eter 1200 ft. (366 m.). Halematjmau from S.E., showing islands and benches 

 on the left, overflow floors on the right. Swift current around South Island 

 in foreground. Strong overflow in progress, culmination of winter rise. 

 Compare map, fig. 2, p. 168. Photo, Morihiro. 



