I 



58 



Kilanea and Manna Loa. 



the viscid mass, but in quantities too small to run off far. Consequently it solidified on the margin, 

 and thus formed the high rim which confined the lavas. Twice or at two points while we were there, 

 the liquid flood broke through the rim, and flowed off in a broad, deep channel which continued its 

 flow until we left the volcano. The view was a new one, and thrilling beyond description. 



lu Jtily, 1844, Mr. Coan saw the large lake overflow on every side, spreading 

 over the whole southern end of the crater to the base of the black ledge and concealing 

 the outlines of the raised rim. Two deep fissures extended under the ledge nearly 

 encircling that part of the crater, and one of these was one hundred feet deep. The 



diagram given in Mr. Coan's letter 

 1844 (which has not been published in 



full) is here reproduced as ren- 

 dering clearer the geography at the time. 

 Dana considers the canals as mysteries, but 

 the explanation he gives (Charaderistics 

 of Volcanoes, p. 77) only substitutes one 

 mystery for another. We will continue the 

 record and overtake his explanation. 



In June, 1846, Mr. Coan writes^'' 

 1846 that "the repeated overflowings 



had elevated the central parts of 

 the crater four or five hundred feet since 

 1840, so that some points are now more 

 elevated than the black ledge." We may 

 note that the rise in the floor level was due, 

 according to this practised observer, to the 



overflow of the lake which filled up the lower levels, including the canals. A month later 

 Rev. Chester S. Lyman was at the crater and found it much as the last observer had 

 reported. The canal was nearly filled by overflows, and in places nearly obliterated." 

 A rude sketch which Mr. Lyman left on the islands is here reproduced, and 

 with this chart we may understand the explanation of the rapid rise of the bottom of 

 Kilauea given by Mr. Lyman and adopted by Prof. Dana.'** A crescent shaped ridge 

 of rocks is shown on this sketch, and Lyman states that it was a continuous ridge more 

 than a mile long, consisting of angular blocks of compact lava resembling the debris at 

 the foot of a range of trap or basalt. From this he infers that the ridge once constituted 

 a talus or accumulation of debris on the floor of the walls of the lower pit of 1840: 



FIG. 46. DIAGR.\M IN THE COAN LETTER. 



■"'Amer. Journ. Science, 1850, x, 361. 

 "Amer. Journ. Science, 1851, xii, 75. 



^'Prof. Lj'inan's plan, as given by Dana (Characteristics of Volcanoes, p. 79), is quite different from the plan 

 he left on the spot and which is copied above. It must have been elaborated at New Haven from notes. 



[436] 



