Recent Eruption of Manna Loa. 115 



the positions where these opened fissures reached the sea. 

 Any internal force sufficient to break through the sides of a 

 mountain like Mauna Loa, must necessarily produce a linear 

 fissure, or a series of fissures, and not a single tunnel-like 

 opening. 



7. We have yet received no definite facts as to the angle 

 of slope down which the lavas descended. Yet we do know 

 that in this and in a former eruption the stream continued 

 over the declivities for thirty miles, and these declivities 

 have an average angle of six or seven degrees, though made 

 up of subordinate slopes varying probably between one and 

 twenty degrees, as Mr Coan mentions, when describing the 

 descent of the lavas in the summit eruptions of 1843. The 

 slopes of Mauna Loa, although the mountain is over 14,000 

 feet high, are therefore not too steep to receive accessions 

 from top to bottom, from eruptions of vast extent over its 

 sides. With such facts, in connection with others brought 

 forward by the writer, we are assuredly sustained in not ad- 

 mitting the universal application of the so-called elevation 

 theory. But in rejecting this theory, we do not go to the 

 opposite extreme, and adopt in its full extent the overflow 

 theory. The truth, as usual, lies between the two extremes, 

 as the writer has elsewhere urged. Both causes have acted 

 in the history of all volcanoes ; both act from the very com- 

 mencement of the germ-cone. There is elevation from the 

 central action, from the opening and filling of fissures about 

 the centre, and also from the outflow of lavas. The first of 

 these operations may be most effective in the earlier periods 

 of the rising mountain ; but each continues to act till the fires 

 die out; and in the later periods, especially, there is often a 

 flattening process, arising from the spread of lavas ejected 

 from fissures about the base of the mountain, which extend 

 the shores, and diminish the angle of slope. 



8. The interval of time between the last three erup- 

 tions of the central crater of Mauna Loa is from nine to ten 

 and a half years. The first of these three took place in June 

 1832; the second in January 1843; the third in February 

 1852. The recorded eruptions of Kilauea have occurred 

 as follows, leaving out that of 1789 : the first in 1823, the 



n 2 



