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



where it approached the Great Lake." Another remarkable 

 feature of related import, was the existence generally of a 

 trough, or "canal" as it had been called, between the ridge 

 and the margin of the ledge, " several rods in width and in 

 some places 40 or 50 feet in depth." The ridge looked highest 

 from the black ledge side, the ledge being lower than the inte- 

 rior plain. Following it southward, the slope on the interior 

 side diminished in height, and finally run out, while on the 

 black ledge side, the elevation increased until the slope 

 became a precipice over 100 feet high, which was so steep at 

 "its southeastern limit that stones hurled from the hand 

 cleared the foot of the bluff." The stones were " nearly three 

 seconds in falling, which would give for the perpendicular 

 elevation the amount just stated," [or between 140 and 150 feet.] 



The "canal," as was learned from Mr. Coan, had been filling 

 up, from a previous depth of 200 feet, by flows of lava from 

 the Great South Lake. On one occasion the lake, " filled to 

 the brim," poured out two streams, from "nearly opposite 

 points of the lake," which followed the broad canal of either 

 side, fifty or more feet deep and wide, " until they came within 

 half a mile of meeting under the northern wall of the crater, 

 thus nearly enclosing an area of about two miles in length 

 and a mile and a half in breadth."* In 1846, it was nearly 

 filled, and in some parts entirely obliterated. 



After a survey of the facts as to the position and nature of 

 the long ridge of lava blocks and comparing with the condi- 

 tion in 1840, Mr. Lyman concluded that the ridge "once con- 

 stituted a talus, or accumulation of debris," on the floor at the 

 foot of the walls of the lower pit of 1840 ; that the floor with 

 its margin of blocks had " been elevated, partly by upheaving 

 forces from beneath, and partly by overflows from the Great 

 Lake and other active vents," until the talus overtopped "the 

 precipice at the foot of which it was accumulated." He adds : 

 " The phenomenon seems inexplicable on any other hypothesis 

 than that of the bodily upheaving of the inner floor of the crater." 

 " When visited by the Exploring Expedition in 1840, the sur- 

 face of the Great Lake was between three and (our hundred 

 feet below the black ledge and measured only 1000 by 1500 

 feet in diameter. Consequently in six years the lake had not 



* Coan, Life in Hawaii, 1882, p. 263. Mr. Coan does not give the date of the 

 event here mentioned ; but no such "canal " is in the record except that of 1846. 

 The time of the first recognition of the canal is not stated. It is certain that 

 the "two deep fissures" of July, 1844 (Coan, this Journal, II, ix, 361, and my 

 Exped. Rep., p. 193), were not the two sides of the canal ; for they were opened 

 " under the black ledge" and encircled "the whole southern area," while the 

 Lyman canal encircled the whole interior of Kilauea. Further, as Mr. Coan says, 

 these fissures around the southern area soon became filled with lava that was 

 pouring over from the lake; while the "canal " was to a large extent unfilled in 

 1846. 



