90 J. D. Dana — Eruptions of Kilauea and Mt Loa. 



orifice of the crater, too low down for the air-current to have 

 got into action ; and in such cases there is an obvious source for 

 the condensed moisture, and that is, the liquid lavas of the 

 crater. Mr. Green expresses the fact well in the words (p. 169) 

 " There is very often a large quantity of smoke seen to arise 

 from the orifices of eruption, and this often spreads out in the 

 higher regions of the atmosphere. There was a column, per- 

 haps 500 feet wide and 10,000 high, arising from the orifice of 

 1859 when we pitched our tent along side it," at a point on 

 the mountain 10,500 feet above the sea-level. 



Further (5), the feeble amount of vapor observed by him in 

 1873 oyer the fountain in the summit-crater, so unlike what 

 had existed a few days before, may have its explanation in the 

 dryness of the atmosphere at the time. The air is generally 

 dry at the summit, but must have its phases of unusual dry- 

 ness, during which an unusual amount of escaping moisture 

 would, for this reason, become invisible. 



(7) The summit fountain is a combination of jets, each of 

 which must have had its initiating projectile act ; and it con- 

 tinues for weeks and months ; and this is at variance with the 

 evidence from Kilauea, which makes the ascensive action very 

 gradually and quietly Jifting, instead of projectile. 



Finally (8) the cold atmospheric air carried down into a lava- 

 lake by the jets could generate very little projectile power. 

 The air, on entering the lavas, would encounter a temperature 

 near 2000° F. if not beyond it, and hence the expansion would 

 cause expulsion, or a speedy escape, in spite of any currents or 

 intestine movements that might exist in the boiling cauldron. 



For these reasons we may conclude that the old and gener- 

 ally accepted explanation which attributes the projectile action 

 chiefly to water- vapor is not seriously invalidated by the in- 

 genious suggestions brought forward by Mr. Green. 



Part III.— ERUPTIONS OF KILAUEA AND MT. LOA. 



In the following pages the subjects considered are : I. The 

 characteristics and causes of eruptions ; II. Metamorphism 

 under volcanic action ; III. The form of Mt. Loa as a result 

 of its eruptions ; I V. The relations of Kilauea to Mt. Loa ; 

 Y. General volcanic phenomena. 



Under the head of Eruptions, the principal topics are : the 

 kinds ; the places of outbreak ; the causes of eruptions ; the 

 characters of the lava streams ; the positions and origin of the 

 subordinate lateral cones. 



