CAUSES OF VOLCANIC ACTIVITY DAY 269 



That the gases from these different sources differ in composition 

 is abundantly shown by their continual reaction wlien they meet in 

 the lava lake, as has been explained in the earlier part of this paper. 



That the fluid material in these individual pockets is under dif- 

 ferent pressures as well as different temperatures is also shown by 

 many observations of small streams of lava which emerge from the 

 talus pile, often 100 feet or more above the level of the lava lake, 

 and flow down into it (pi. 3, fig. 2). Such a flow, observed in June, 

 1912, lasted for several days and released a very considerable body 

 of lava. 



If the lava lake represented the outlet of a single subterranean 

 magma chamber with which it is supposed to be connected through 

 a single neck or funnel, then the establishment of a second conduit 

 from one to the other Avill not be competent to deliver lava at a 

 higher level than the first, or gases of different composition. A 

 separate chamber and an additional source of energy are necessary 

 for that. Thus it has happened that the heterogeneous character of 

 the gases collected, the temperature conditions within the lava basin, 

 the appearance of the crater when free of all its liquid lava and 

 the dynamic relations within the lava body when present in the 

 crater, all point to many sources rather than to a single source both 

 of gases and of magma. 



An interesting sidelight of quite another kind has lately been 

 thrown on this problem from an entirely unexpected source. In 

 the month of July, 1919, Professor Jaggar took advantage of a favor- 

 able opportunity to make a continuous series of observations, extend- 

 ing through the entire month, of the level of lava in the basin of 

 Kilauea. The observations were made by vertical triangulation from 

 datum points on the rim oi the pit at intervals of 20 minutes day 

 and night with the purpose of ascertaining whether or not a lunar 

 or solar influence upon the lava mass could be established. The 

 examination of the data was made by E. W. Brown," than whom 

 there is no one with wider experience in the discussion of tidal 

 phenomena, and although the curves at first sight appeared to be of 

 periodic character and were so regarded by Jaggar, no more than 

 an inch or two in apparent changes of several feet could be attrib- 

 uted by Brown to luni-solar influence. Had the magma chamber 

 been very large, an unmistakable tidal effect would certainly have 

 been found. 



And so we return from this investigation also to the conclusion 

 that volcanoes are local and superficial developments representing 

 (geologically) the last stages of crystallization in a mass of magma 

 below, of which little remains fluid and this in small (as geologic 



'"Kiiiest W. Brown, "Tidal Oscillalious In naleniauman, the Ijiva I'll of Kllani-a," Am. 

 Journ. Scl. (5), 9, 95, 1925. 



