J. D. Dana — History of the Changes in Kilauea. 363 



tend along planes through the large masses, like those of the 

 exterior. But in these as in other parts, it is evident that the 

 agency was tearing and up-ploughing, and cavity-making in 

 its action, and not vesiculating. At one place great slab-like 

 masses of very compact rock, 20 feet or more long, stood verti- 

 cally together, each about 8 feet high and 3 to 10 inches thick, 

 with a curving over at top, somewhat like gigantic shavings. 

 Ellis, in the "Journal" of the Hawaiian tour of the Mission 

 deputation in 1825, appears to describe similar occurrences 

 over the aa fields in the following words: 



" Slabs of lava from 9 to 12 inches thick and from 4 to 20 

 or 30 feet in diameter, were frequently piled up edgewise or 

 stood leaning against several others in a similar manner. Some 

 of them were 6, 10, or 12 feet above the general surface." 



These piles of jagged rocks have usually a height of 25 to 

 40 feet above the level of the adjoining smooth-surfaced stream, 

 owing this height evidently to the large spaces among the 

 blocks. 



The above figure represents the features of such a stream. 

 The title of such piles of blocks to the name of a stream would 

 not be admitted were it not proved that they are formed during 

 the progress of a lava-flow ; that a lava-stream may change 

 from the smooth-flowing or (pahoehoe) condition to the aa, 

 and back again to the smooth-flowing ; and that the same vent 

 may give out at one and the same time, a smooth-flowing stream 

 in one direction, and an aa stream in another. The Mt. Loa 

 stream of 1880-81, is mostly a smooth-surfaced stream ; but 

 over part of it, within six miles of Hilo (where I went under 

 the guidance of Kev. E. P. Baker, a close student of the Ha- 

 waiian volcanoes), the pahoehoe stream changed for a few hun- 

 dred yards to aa, with evidences of transition between them. 

 Further, Mr. Furneaux, an artist, informed me, in his studio 

 at Honolulu, that he was at the head of the flow of 1880, on 

 Mauna Loa, when it was in progress ; that one of the three 

 streams which was then flowing from the vent — that going 

 southeastward — was of the aa kind, while the other two were 

 smooth-flowing or pahoehoe; that he saw the aa stream very 

 gradually advancing, the sides apparently motionless, but about 

 the front, now and then a block tumbling down from above; 

 and the blocks toward the foot at intervals making a shove 

 onward, and rather gaining on the bottom portion where there 

 was impeding friction ; and he noticed a red heat between some 

 of the blocks in the front portion. He had in his studio a paint- 

 ing of the scene. 



In some aa streams, however — probably the thinner streams — 

 the"masses are much smaller and more scoria-like than above 



