J. D. Dana — Summit Crater of Mt. Loa. 

 1. Times and Time-inter vaU of Eruptions. 



83 



1. Question of Periodicity. — Commencing with the eruption 

 of 1832, there have been nine registered eruptions of Mt. Loa. 

 Their times and heights of outflow, directions and lengths of 

 stream, and relations to earthquakes, are stated in the following 

 table : 





Reported 

 Earthquakes. 



Height of chief 



Direction and 





out-flow. 



length of flow. 



1. 1832: June 20, 2-3 weeks 



none. 



Summit. 



No outflow. 



2. 1843 : Jan. 9 to end "Feb., 1% mos. 



none. 



11,000. 



N.N.W., 15 m. 



8. 1851 : Aug. 8, for 3 or 4 days,.. 



none. 



12,900. 



W., 10 m. 



4. 1852 : Feb. 1*7 into March, 20 d'ys 



none. 



little over 10,000 



E., 20 m. 



5. 1855: Aug. 11 to Nov., '56, 15 ms 



none. 



12,000. 



E., 26 m. 



6. 1859: Jan. 23 to Nov. 25, 10 mos. 



none. 



10,500. 



N.W., 33 m. 



7. 1868: March 27, 16 days, 



earthquakes 



3,000. 



S.. 10-1 lm. 



8. 1880 : Nov. 5 to Aug., '81, 9 mos. 



none. 



11,100. 



E., 30 m. 



9. 1887: Jan. 18, 10 days,... • 



earthquakes 



5,600. 



S. 14 m. 



The intervals between these eruptions, reckoning (A) be- 

 tween their beginnings, and (B) between the end of each and 

 the beginning of the following one, are : 







A. 







B. 





Between eruptions — 1 and 2 



10 



years 



8 mos. 



10 



yean 



7 mos 



2 and 3 



8 



a 



7 " 



8 



a 



54 " 



3 and 4 







61 « 







6 " 



4 and 5 



3 



a 



6 " 



3 



u 



5 " 



5 and 6 



3 



a 



5 " 



2 



u 



2 " 



6 and 7 



9 



a 



2 " 



8 



a 



4 " 



7 and 8 



12 



a 



7 (i 



12 



a 



7 " 



8 and 9 



6 



a 



n " 



5 



a 



6 " 



The eruptions above enumerated, that of 1832 perhaps ex- 

 cepted, were great eruptions ; that is they had outside or subaerial 

 outflows. But the history shows that at other times in the 

 sixty-five years the summit of the mountain has been often 

 brilliantly lighted, and surmounted with a column of clouds of 

 great height, made apparently from the escaping vapors, which 

 became a lofty column of light at night. These summit illumin- 

 ations have been shown to be evidence (p. 27) not merely of ac- 

 tion in or about the crater, but decisively of a boiling or foun- 

 tain-like activity in the liquid lavas, if not also of out-flowing 

 streams. The drifting of Pele's hair on such occasions 35 miles 

 to Hilo is as good testimony to the playing of jets or fountains 

 as a note from an observer at the summit. 



Moreover, we have learned from Kilauea that these times of 

 brilliant action within the crater may be followed by subter- 

 ranean or submarine discharges when not by subaerial ; and 

 therefore that they are not always merely the flaring up and 



