168 Jaggar, Jr. — Outbreak of Mauna Loa, Hawaii, 19 H. 



maxima, extending over several minutes. No shocks were 

 registered after the mid-afternoon. These shocks attracted no 

 attention except instru mentally, showing that the statements 

 that the outbreaks of Mauna Loa are frequently unheralded by 

 shocks of earthquake are loose assertions, and refer only to 

 earthquakes of perceptible magnitude. The action of the 

 instruments about noon on ~Nov. 25 was so peculiar that Mr. 

 Wood called my attention to it and mentioned the probability 

 that an outbreak of Mauna Loa was the cause. 



Kilauea cannot be said to have shown the slightest instan- 

 taneous sympathy with the Mauna Loa revival. Throughout 

 1914 Kilauea has gradually increased in the activity of a rising 

 lava column, following upon marked dormancy in 1913. As a 

 whole the lava column of Kilauea rose gradually from 1906 to 

 1910, its revival taking place just before the culminating out- 

 flow of Mauna Loa in 1907. In the winters of 1910 and 1912 

 the Kilauea lava column rose to within sixty feet of the rim of 

 the Halemaumau cone, but did not overflow. Since 1912 the 

 lava has gradually receded, and even now, while brilliant, is 

 very low, 460 feet below the rim. There were thus three 

 years of rise, two years of high level, and three years of subsi- 

 dence in Kilauea, with minor semi-annual and monthly fluctua- 

 tions. And this term of eight years checks closely with the 

 repose period of Mauna Loa. If the lava of Kilauea disappears 

 in 1915, and during the term of the active epoch of Mauna 

 Loa remains dormant, we may well suspect a sympathy of 

 alternation between the two volcanoes. 



During the week of Nov. 15, 1914, Mr. Conant of Kona, 

 with Charles Ka as guide, went to the summit crater of Mauna 

 Loa, Mokuaweoweo, and found conditions as usual, the 1907 

 cone on the floor of the crater just as it has been in the last 

 eight years, with a few sulphurous cracks vaporing on the 

 floor near the cone. Therefore, in the week before the out- 

 break there was no significant visible change. At the observa- 

 tory, notes have been kept for months past on the appearance 

 of Mauna Loa, not a trace of vapor being seen above Mokua- 

 weoweo. From time to time since 1912 high thin vapor col- 

 umns have been recorded rising several hundred feet above 

 three old conelets on the northeast rift line of the mountain, 

 the highest of many such cones which appear in profile from 

 the observatory, and about in the position where the next flow 

 might be expected. This locality has not been vaporing of 

 late, nor has it been especially active this year. 



On the afternoon of Nov. 25", 1914, Wednesday, shortly 

 before four o'clock, the observatory was enveloped in a driz- 

 zling mist, but at Pahala on the southern flank of Mauna Loa 

 the summit was clearly seen and a column of white vapor sud- 

 denly rose from the north side of the summit ; then four other 



