February 26, 1886.] 



SCIENCE. 



181 



the island of Sumbawa, and the date of its 

 formation was 1815. The incidents of this last 

 eruption were investigated by Dr. Jmighuhn, 

 whose work on the volcanoes of the East Indies 

 is now a classic one in the annals of volcanism. 

 Judging from his account, this must have been 

 the most energetic and destructive explosion 

 of which any authentic account has been pre- 

 served, surpassing greatly that of Krakatoa. 

 Prior to the outbreak, Tomboro was a shapely 

 cone, rising a few miles from the shore to an alti- 

 tude of more than 9,000 feet. In a single night 

 the upper 5,000 feet was blown into fragments, 

 which were scattered over thousands of square 

 miles of sea and land ; while the volcanic dust 

 darkened the air over a million square miles of 

 island and ocean. Many months afterward, 

 when the scene could be visited, Tomboro was a 

 mere stump of a mountain, with a large crater in 

 the place of the cone which had been blown 

 away. Other instances of a similar nature might 

 be mentioned, but the foregoing may suffice. 



We have, then, examples of depressions similar 

 to that of Crater Lake produced by two very dif- 

 ferent modes of action. To which of them may 

 we refer the origin of the magnificent crater of 

 the Cascades ? Just at present a confident answer 

 cannot be given ; for the ground has not been 

 sufficiently studied. The facts brought to light by 

 the first hasty reconnaissance seemed to indicate 

 the explosive action, rather than the quiet method 

 of subterranean fusion. But it is best to await 

 the results of a more critical examination before 

 committing ourselves to any opinion. It may be 

 well, however, to state such facts as have already 

 come to light, as well as some general considera- 

 tions pertinent to the subject, and let them pass 

 for what they are worth. 



1°. In the Hawaiian calderas the evidences of 

 sinkage are conspicuous. They are not confined 

 to the deeper floors of the pits, but are also seen 

 in the partial subsidence of great blocks or slices 



j of the walls immediately enclosing them, and in 

 irregular sunken spots in their vicinity, also in 



i the marks of powerful shearing or faulting action 

 in the walls themselves. They appear to be cor- 

 related to the remarkably quiet habits of the 

 Hawaiian volcanoes, to their habitual modes of 

 eruption, and to the special structure of the vol- 

 canic piles, which do not rise in steep conical 

 peaks, but are very broad and flat. At Crater 

 Lake, neither in the walls themselves, nor in the 

 immediate neighborhood back of the crest-line, 

 have any traces of sinkage been observed as yet. 

 Nothing can at present be pointed out which sug- 

 gests the Hawaiian mode of origin, beyond the 

 fact that a vast crater is before us. The general 



structure and habits of the Cascade volcanoes are 

 indicative of a more vigorous style of volcanic 

 action than the Hawaiian. 



2°. Crater Lake is the centre, and, without much 

 doubt, the source, of an extraordinary quantity of 

 andesitic pumice and tuff, which is scattered far 

 and wide over a circle of country ranging from 

 40 to 60 miles in diameter. It often lies in beds 

 several hundred feet deep, and covering hundreds 

 of square miles. This pumice is not such as is 

 often seen in some lava streams, but consists of 

 rounded masses and pellets which seldom exceed 

 a cubic foot in volume, and grade down to fine, 

 light sand. It is the kind which is blown violently 

 from a volcano during eruption, and projected high 

 in air, to fall in showers over the surrounding- 

 country. It is found on the loftiest peaks and 

 mountains anywhere within 20 miles of the lake, 

 and assuredly did not emanate from the peaks on 

 which it now lies. Vast quantities of it have been 

 gathered up by the rains and streams (for it is 

 lighter than cork), and swept eastward into the 

 broad basins of Klamath Marsh and Klamath 

 Lake, or carried westward through the Rogue 

 River into the Pacific. The finer lapilli and sand 

 have been consolidated into beds, which flank the 

 eastern slope of the Cascades, and are also found 

 west of its divide in the flatter spaces beyond the 

 base of the truncated pile which holds the crater. 

 These are well exposed in the walls of little box- 

 canons two or three hundred feet deep, and the 

 tuff weathers out into pleasing columnar forms. 

 The tuff is older than the pumice, for, wherever 

 the two were seen together, the tuff was under- 

 most. This light fragmental material, its wide 

 distribution in every direction, with the lake as 

 the centre of dispersion, the very light and 

 highly vesicular character of the pumice, — all 

 indicate that at some time Crater Lake has been 

 the scene of some sort of very energetic volcanic 

 action. 



3°. But there is a weak point in the argument. 

 If a large cone, composed of solid lavas such as are 

 now seen in the w^alls of the lake basin, has been 

 blown into rubble, and the fragments hurled far 

 and wide over the surrounding country, ought we 

 not to be able to recognize them in vast abundance 

 in the vicinity? Most certainly we ought to. 

 And yet in close proximity to the lake no frag- 

 ments were noted, except such as we always ex- 

 pect to find at the foot of steep spurs and ridges 

 of volcanic rock, and which have broken down 

 from them in the ordinary course of weathering. 

 This absence of the corpus delicti is a serious dif- 

 ficulty in the way of a speedy conclusion that the 

 mountain was blown up by any such summary 

 proceeding as Tomboro or Krakatoa, and indicates 



