266 ANNUAL OF SCIENTIFIC DISCOVERT. 



It passed over a distance of about 3 miles in as many minutes, and 

 then ceased. 



An eruption broke out on Maun a Loa on March 27th, the lava 

 running down the sides of the mountain in four streams, in a south- 

 erly and easterl}^ direction. On the 28th the flow had gone about 

 10 miles due south from its source, and on the 29th had advanced 

 15 miles further. Near Kahuku a lava stream burst out from a 

 crater about 10 miles up the mountain, on the morning of April 

 7th, and in the afternoon of the same day from a new one several 

 miles lower down, the stream running 5 miles to the sea. This 

 river of fire was from 200 to 800 feet wide, and, as the descent was 

 2,000 feet in 5 miles, the statement that it ran 10 to 25 miles an 

 hour will not be doul)ted. The eruption lasted 5 days. On the 

 evening before the eruption the ground throughout the district 

 was covered by a shower of fine sand and light pumice-stone, of 

 a light yellowish color, probably coming from some vent-hole near 

 the summit-crater. The tidal wave here rolled in over the tops of 

 the cocoanut trees, probably 60 feet high, completely annihilating 

 several villages. 



The source of the disturbance was evidently directly beneath 

 Mauna Loa, and not far, if at all, below the level of the part of the 

 ocean's bottom lying within the Hawaiian seas, and the phenome- 

 non was therefore eminently a local one. The submarine rocks 

 of the island are every where cavernous, and must all have cavities 

 filled with water from the superincumbent ocean. Mauna Loa, 

 though nearl}" 14,000 feet high, and 3,000 square miles in area, has 

 only 1 or 2 surface streams over more than' three-fourths of this 

 area. The greater part of the moisture which falls annually on 

 these cavernous lavas becomes subterranean. The vertical chan- 

 nels of the mountains, filled by the rains, must have brought im- 

 mense hydrostatic pressure upon the deep water-chambers ; the 

 water may thus have been forced deeply into the hot rocks, and, 

 there, suddenly converted into steam, have caused new fissures, 

 with attendant earthquakes, and have opened passages to hotter 

 fires ; thence came vaster rendings of the mountain and severer 

 shocks, and, as a natural sequence, all that subsequent!}^ took 

 place. — American Journal of Science, July, 1868, and Jan., 1869. 



THEORY OF VOLCANOES. 



From the observations of Mr. W. T. Brigham, in *' Memoii*s of 

 the Boston Society of Natural History," vol. i., part 3, on the vol- 

 canoes of the Sandwich Islands, it appears that, although the cra- 

 ters of the group occur along a lijie supposed to be a line of fissure, 

 as in other regions, the major axes or directions of the craters 

 were parallel to one another at an angle of 26° from the trend of 

 the group; in other words, the supposed volcanic fissure trends 

 N. 04° W., the major axes being north and south. Following out 

 this idea he ascertained that the mtijor axes of craters are always 

 at riglit angles to the mountain chains in which they are situated. 

 He concludes that the theory of an unequally contracting crust, 



