ATMOSPHERIC PHENOMENA.
A column of smoke constantly arose from the points of ejec tion, visible on all sides. It expanded as it arose, and closely re sembled the so-called "pine tree" shown on photographs of erup tions from Vesuvius. The northeast trade-wind does not reach the altitude of the outbursts ; hence the vapors may arise vertically and be spread out on all sides like an enormous umbrella. While the south wind blew, the smoke cloud reached Honolulu, two hun dred miles distant. Some people observed a distinctly sulphurous odor, while one gentleman asserts that he had been clearly struck in the face by particles of the volcanic dust. July 17 the steamer "Mariposa" observed this smoke, some six hundred miles to the northeast. Similarly the officers of the "Morning Star" found themselves unable to take the customary observations for latitude at an equally great distance to the southwest. The dia meter of the area obscured must have considerably exceeded 1,200 miles, as the observations reported were much to the north of the major axis.
It was also interesting to observe the presence of an enormous cumulus cloud directly over the crater of Mokuaweoweo. This was developed by the rising of heated vapors from the summit crater coming in contact with a cooler atmosphere ; and was ob served by myself July 14 and 15 from Kau.
Of other notices of similar clouds is that by a member of the Challenger expedition in 1875, which see, ante; and by W. L. Green in 1881, over a flat to the west of Hilo where the lava had got dammed up in its course. In the daytime a waterspout is seen descending from the cloud, while the lower end is being driven off in steam by contact with the hot rocks. By night the cloud has a blood-red color. Mr. Green ascribed the phenomena to the indraught of moisture-laden air towards the heated area— the vapors being condensed when they arrive over a cooler stratum.
Analogous appearances have been seen in connection with fires, as in the case of the Chelsea, Mass., conflagration of April 12, 1908. A. L. Rotch says the air was rather dry that day so that the formation of the cumulus clouds some few miles high was not so easy. B. M. Varney says these cumuli were imperfectly formed, and they did not appear directly over the fire, but a considerable distance to the leeward. In December, 1896, clouds were more perfectly formed over the burning of a coal pocket belonging to the Boston and Maine Railroad Company.—Seience, May 15, 1908.
Concerning the appearances in Mokuaweoweo July 13, Pro fessor Ingalls writes : "The floor of the crater was of black lava, to all appearance precisely like that of Kilauea, with a few rough patches here and there which I believe was `a.a.' Extending in a direction roughly parallel with the west wall, from the talus at the base of the lower terrace at the north pretty nearly to the gap in the south, there stretched a crack in the crater floor, all points of which lay slightly west of the medial north-and-south axis. From various places along this fissure rose up nearly all the signs of the exist ence of the volcanic fires beneath, these evidences being sickly jets of steam, rising in such a manner as to suggest no urgency from below ; also at the bottom of the southwest wall the talus ap pears to be undergoing a transformation into sulphur banks. There was nothing in the appearance of this summit crater to warrant an assumption that at this very time, at the depth of 3,00o to 3,50o feet below the level of this flood, there was a genu ine volcano in terrific eruption." 28