J. D. Dana — History of the Changes in Kilauea. 17 



sustained, after explanation (xxxiii, 440), may need reduction on 

 the ground that the present width of the crater is greater than 

 in 1825, owing to falls of the walls ; but it is useless with 

 present knowledge to make any definite correction. Only 

 general results are possible. 



After the 1832 eruption, the lower pit in February of 1834, 

 was 362 feet deep, by the barometric measurement of Mr. 

 Douglas,* and in May of 1838, about 4^ years later it was 

 filled to within 40 feet of the top ; whence the mean annual 

 rate of 71|- feet. 



After the 1840 eruption, between January, 1841, and the 

 summer of 1846, 5^ years, the 342 feet of depth, found for the 

 lower pit by the Wilkes Expedition, was obliterated, and the 

 floor was raised on an average 40 or 50 feet beyond this ; a rise 

 of 400 feet m the 5|- years would give for the mean annual 

 rate, T2| feet. 



Subsequent to 1846 the rising of the floor was slower. 

 Between 1846 and 1868, 22 years, the rise over the central 

 plateau is estimated at 200 feet. It is not certain that subsi- 

 dences in the plateau of greater or less amount did not take 

 place at the eruptions of 1849 and 1855, or at other times. 



3. Levels of the floor after the eruptions of 1823, 1832, 1840, 1868 



and 1886. 



The measurements of depth already given and the mean 

 annual rate of progress deduced are approximate data for 

 determining the depth of the lower pit as it existed immediate- 

 ly after the great eruptions. 



The deyjth after the 1823 eruption is considered above. To 

 arrive at the depth after the 1832 eruption, the depth obtained 

 in 1834 by Douglas has to be increased by an allowance for 

 change during the previous year and a half, which, at the rate 

 arrived at above, would give 450 feet. This is so much less 

 than the estimate of Mr. Goodrich (xxxiii, 446) that it is 

 almost certainly below rather than above the actual fact. For 

 the depth in June 1840, the Wilkes Expedition measurement, 

 342 feet, should be increased for a preceding interval of seven 

 months, which at the rate deduced above for the next four 

 years, would make the amount about 385 feet. In 1868, 

 according to the two estimates for the lower pit (xxxiv, 92), 

 the depth was about 300 feet. Mr. Severance of Hilo, in- 

 formed me in August last that the pit in 1868 was as deep as in 

 1840. The lower estimate is adopted beyond. In 1880, the 

 lower pit of 1868 had wholly disappeared, and, according to 



* See the first part of this paper, vol. xxxiii; p. 446, June, 1887, where the facts 

 are definitely given, and also other evidence. 



Am. Jour. Sci.— Third Series, Vol. XXXV, No. 205.— Jan., 1888. 

 2 



