30 



KNOWLEDGE cS: SCIENTIFIC NEWS. 



[Fedruaky, 1907 



With these preliminary remarks we may introduce 

 some of Professor Pickering's photofjraphs of Hawaiian 

 volcanoes. Mud volcanoes and cinder volcanoes are repre- 

 sented in Hawaii. Tlie Diamond 1 lead crater isof volcanic 

 tufa, and bears an exterior resemblance to the craters of 

 the Moon ; but its floor is at a higher level than the 

 exterior plane and its outer slope steeper than its inner 

 one, so that this crater, toj;ether with all the cinder 

 cones, may be dismissed as having no known counter- 

 part on the Moon. 



The Hawaiian lava craters, however, on the other 

 hand, present a close resemblance in many respfctsto 

 lunar formations. The first subdivision (a), the lava cones, 

 are most strikingly represented by Mauna Loa, by far 

 the world's largest volcano. Us base lies 15,000 feet 

 below the level of the sea. Nevertheless, its summit 



Fig. 7.— Scblckard and Pbocylidcs. 



crater is so large compared to its depth that photography 

 could not very well show its characteristic features, and 

 accordingly Professor Pickering chose a smaller example, 

 a small lava cone in Haleakala as the typical example of 

 this form of crater. 



The terrestrial tall volcanic cone, with the compara- 

 tively minute crater at the top, was supposed to be 

 absent from the Moon. But a recent examination of a 

 lunar photograph taken at the Yerkes Observatory by 

 Professor Ritchey shows that there are some small 

 examples. One of these is probably visible in fig. 3, 

 which is a lunar photograph of Kies and Mercator. 

 Between them is to be seen a small cone with a minute 

 crater at its summit. It is not unlike Vesuvius in size 

 and shape. 



We next come to lava pits (b). In the lunar photo- 

 graph of Bullialdus is a pair of coneless lava pits, just 

 above the huge crater. A few other very minute pits 

 are shown on the photograph, but all the larger ones 

 have cones. 



In Fig. 4 we have" a small terrestr^il pit of this type- 



It is known as Kauhaku ; and has no exterior cone 

 whatever; it is simply a hole in the ground. 



Great attention was bestowed by Professor Pickering 

 on the method of formation of crater rings, the third sub- 

 division of lava craters ; and he experimented with iron 

 slag to obtain object lessons of the methods of formation 

 of craters. But the great central pit of Kihuiea, Hale- 

 maumau, supplies object lessons on a larger scale. When 

 Ilalemaumau is really active, the sight is said to be grand 

 beyond description. Lakes of liquid lava occur both 

 within and without it. Numerous lire fountains from 

 10 to 50 feet in height play over the surface of these lakes. 

 At times the surface solidifies, then suddenly a crack will 

 run across it, and in a few minutes the who'e solid 

 material will break up into separate cakes, which will 

 presently turn on edge and sink beneath the surface of 

 the lake. These lakes are specially interesting, since 

 about them are found crater rings which seem 1 1 be 

 analogous in appearance to the larger cratir formations 

 in the Moon. 



In itS, o the pit overflowed, the lava pouring down and 

 filling a neighbouring dejiression. At the time of an 

 eruption such as this the lava rises, overflows, and cools, 

 thus forming a raised rim or circular dam. Such a rim 

 is shown on a large scale in figs. 5 and 6, the cakes of 

 lava appearing like broken cakes of ice. In fig. 7 is 

 shown a portion of the Moon near the limb so as to present 

 the craters obliquely. It will be noted that the two large 

 craters there depicted, namely, Schickard and Phocylides, 

 both present a form similar to the craters of Halemau- 

 mau. The chief one, Schickard, measures 134 miles in 

 diameter. 



(To be continued.) 



The Bogoslofs and Earthquake 

 Distvirba.nce. 



Mr. V. A. Black writes in regard to the article in last 

 month's " Knowledge " on the Bogoslof Islands : — 

 Whether there is any direct connection between the 

 birth of this island and the recent severe earthquakes at 

 San Francisco and Valparaiso — not to mention the 

 activity of Vesuvius in our own continent — can only be 

 conjectured. The new- island would seem to be about 

 3,500 miles from Valparaiso, and about 1,500 miles 

 from .San Francisco. It certainly cannot be overlooked 

 that the emergence of this island synchronizes with the 

 occurrence of severe earthquakes on the eastern shores 

 of the Pacific, thoug"h at a g^reat distance from the posi- 

 tion of the island, just as the sudden appearance of 

 firevwingk synchronized with the occurrence of earth- 

 tremors and eruptions in Alaska, and with the terrible 

 eruption in Krakatoa. Krakatoa is situated in the 

 neighbourhood of the south-western shore of the Pacific, 

 and, like San Francisco and \'alparaiso, it is at a very 

 great distance from the position of the Bog-oslof Islands. 

 Whether the emergence of the first of the three islands 

 also synchronized with similar phenomena is uncertain. 

 The appearance of this new island emphasises what 

 we are often apt to overlook, notwithstanding our 

 knowledge of the volcanoes and geysers of Iceland, at 

 the Arctic Circle, and of the activity of Mount Erebus, 

 far within the Antarctic Circle. That is, that in high 

 latitudes, as in low latitdues, subterranean forces are 

 still actively at work, and that terrestrial disturbance, 

 in the form of earthquake or volcano, in one reg^ion 

 mny, not improbably, be accompanied by sympathetic 



