3. Three instances are on record where the fire issued from rents comparatively low down ; preceded by vigorous earthquakes of short duration. These were in 1868, 1887, 1907. In 1851 the flow came from a high elevation and in other respects re sembled those from low down.
4. In one instance, 1887, only smoke and steam issued from the summit.
5. Four submarine discharges or disturbances attended the other phenomena, in 1868, 1872, 1877, 1903.
6. Eruptions are more abundant in the rainy months—Janu ary to May.
7. The intervals between eruptions are irregular—from three months to eleven years.
In the midst of accurate, possible and indeterminate figures for heights, I have selected those that seemed the best for the table, and assume that the molten lava rises gradually from the bottom of the pit after a collapse to the time of the next culmination. When there has been an uplift of the cindery blocks by flotation upon the liquid, mention is made of the top of the dome or cone resulting. For the depth of the pit after the first down-plunge, there is the original estimate of Mr. Ellis of eight hundred feet below the black ledge added to the trigonometrical measurement by Lieut. Malden the following year of nine hundred feet for the height of Uwekahuna above the black ledge. In 1834 Dr. D. Douglas figures the depth of the lowest pit at 5,077 feet. Assum ing the correctness of the annual average rise of the pit from 1832 to 1840 of seventy-one and one-half feet, one hundred and forty three feet must be added to 1,077=1,220 for the depth in 1832. His figure for the height of the western wall of seven hundred and fifteen feet above the black ledge would make the depth of the pit three hundred and sixty-two feet, to which must be added forty-three feet more to the molten lava.
For 5840 the figures are those of Captain Wilkes. After this date came the ascensive column of debris floated upon liquid lava three hundred feet high in 1848. As lavas were projected fifty to sixty feet higher in 1849 it is assumed that three hundred and fifty feet will represent the level attained by the liquid. For the depth of the pit there are no data ; and it is assumed that its level may have been the same as in 1840. For the 1855 eruption we have only the estimates of Dr. Coan of six hundred feet for dome above the bottom of the floor of 1840. Mr. Weld was satis fied that the depth of the pit was considerably less than 5,500 feet. If this be placed at 1,200 feet it will conform to the levels both earlier and later.
For 1868 the lower pit is estimated from various reports to have been six hundred feet deep. The black ledge is assumed to have been fifty feet higher than in 5840, or six hundred feet below Uwe kahuna, making this pit 1,200. In 188o the pit had become filled up and the middle portion was higher than its edges ; the whole floor might be styled the black ledge.
Beginning with 1886 the figures for altitudes in this table are supposed to be correct though not entirely satisfactory.
The growth of the black ledge has been continuous. It has been measured at two points; at the base of the western wall, Uwekahuna, and where the trail from the Volcano House strikes it. The following table will show the probable figures: The estimates for the altitude of the cone of Halemaumau have varied greatly, as may be seen by referring to the statements de tailed previously. The one given in i886 by the Government Survey appears to be the most accurate, making a cone sloping one hundred and sixty-three feet to the northeast wall, one hun dred and twenty-five feet to the north, one hundred and five to the western side below Uwekahuna, eighty feet to the southwest. Miss Bird had recognized in 1874 the fact that Halemaumau was a hill top. In 1874 a barometric measurement gave it a height of one hundred and sixty-two feet. C. J. Lyons made its altitude one hundred and seventy-five feet in 1878. Prof. Brigham esti mated it as three hundred and fifty feet in i868.
In 1900 M. M. O'Shaughnessy measured it two hundred and seventy feet. In 1905 W. H. Pickering gave it as two hundred and thirty feet. Our latest estimate is about twenty feet less.
The features of the eruptions from Kilauea may be classified like those from Mokuaweoweo.
1. The influx of lava at the beginning was universal. In one case there seemed to be fire seen from Puna without further erup tion as reported by Mrs. S. J. Lyman, Feb. 21, 1889.
2. Of eruptions from places high up may be cited the flows in Kilauea-iki in 1832 and i868, and from Keanakakoi May 21, 1877.
3. There were three discharges from vents comparatively low clown ; in 1823, from the altitude of 2,700 feet ; in 1840, from the altitude of 1,244, feet and in 1868 from the altitude of 1,700 feet. In the earlier history, the eruptions of 1175, 1340, 1740 and 1788 belong to that class.
4. Emanations of smoke and steam are almost continuous.
5. Only three submarine discharges are mentioned in the table, in 1884 and 1906 and 1907.
In addition to these Kilauea may add another conclusion, that in 1420 and 1790 there were explosive eruptions.
In many of the eruptions from our volcanoes the lava sinks into the earth and is lost sight of. There must be cavities in the in terior capable of holding whatever fluid has been accumulated in the ascensive column. Some of them may be compared with the tunnels beneath the surface flows, or to their mouths, as discerned at the sea level. The deeper down the cavern the smaller will be its dimensions. Even the porosity of the basalts will disappear at great depths.