NOVEMBEB 18, 1910] 



SCIENCE 



725 



It seems to be a very general feature of the 

 structure of the rim that the lowest material, that 

 lying upon the top of the original surface, is a 

 greater or less depth of this powdered rock, some- 

 times alone and sometimes mixed with rock frag- 

 ments, and that on this rests and is supported the 

 whole of the detrital cover which constitutes the 

 crest and outer slopes of the rim. 



This does not look like the result of a single 

 crushing blow from above or steam explosion 

 from beneath. From these the heavier pieces 

 would naturally fall first, and the powdered 

 rock settle on and around them. 



It rather suggests long-continued deposi- 

 tion of this powder, with occasional pieces of 

 rock, by geyser action, and a final explosion 

 or series of explosions that closed the drama. 

 But it has been said there is no evidence of 

 solfataric action here. Thin sections made by 

 the writer from what has been called " meta- 

 morphic " sandstone found in the crater, and 

 met with in borings to a depth of 400 feet 

 seemed to him to differ from geyserite of the 

 Yellowstone Park mainly in enclosing par- 

 ticles of the powdered rock, a thing to be ex- 

 pected of any geyserite formed here. 



In his view, however, all this mass of pul- 

 verized rock has been broken by hot water 

 action; not, of course, by solution which 

 would give amorphous silica, nor by a single 

 violent steam explosion, but in part by ex- 

 plosion of superheated water within the pores 

 of the rock fragments and within the grains 

 themselves, but mainly by attrition of grains 

 and fragments of rock churned by boiling 

 water in geyser tubes. 



Under the microscope the grains of the gray 

 sandstone are seen to contain many minute 

 cavities and inclusions. To test if it was pos- 

 sible to break up these grains by boiling water, 

 a piece of the rock, weighing about 25 grams, 

 was soaked for several days in distilled water 

 and boiled for about 40 hours. 



Disintegration of the cemented grains soon 

 began and was helped from time to time by 

 gentle pressure with the fingers. The water 

 grew turbid with floating particles, some of 

 them so fine that they had not settled on 

 standing 24 hours. 



The dried grains and particles were sifted 

 on an 100-mesh sieve and 28 per cent, passed 

 through. Of these 30 per cent, passed through 

 an 139-mesh bolting cloth. Those passing the 

 139-mesh were mostly angular, those held by 

 it were mostly rounded. 



The grains held by the 100-mesh in the 

 above test were freed from angular particles 

 and again boiled. Gradually the water grew 

 turbid as before. After 30 hours of boiling 

 they were dried and again sifted on the 100- 

 mesh. About 4 per cent, passed through, and 

 of these 11 per cent, passed the 139-mesh. 

 Those passing the 139-mesh were mostly angu- 

 lar, those held by it, for the most part, 

 rounded. 



To test if the grains could be blown apart 

 by steam generated within them, grains held 

 by the 100-mesh were freed from angular 

 fragments, boiled a few minutes to expel 

 air, sealed with water in a glass tube, and this 

 heated in a steel tube to explosion. 



The sifted debris gave many angular frag- 

 ments of grains that passed the 139-mesh 

 along with much powdered glass easily dis- 

 tinguished not only by its behavior between 

 crossed nicols, but by the greater sharpness of 

 its angles and its clearness, the quartz frag- 

 ments, as a rule, being clouded with inclusions 

 and cavities. 



To avoid risk of breaking the quartz grains 

 against the steel tube the experiment was 

 repeated with the glass tube loosely wrapped 

 in asbestos paper. The result was as before. 



These simple experiments seem to show that 

 no other agent than hot water and the ex- 

 plosive power of steam is needed to produce 

 all the phenomena of Coon Butte. 



Geyser tubes coming up through this loosely 

 coherent sandstone, loosening grains and 

 pieces, filling their cavities with superheated 

 water, carrying them up to where diminished 

 pressure let the water explode in steam, burst- 

 ing some, churning them in the tubes, would 

 in time carry up and deposit these millions of 

 tons of grains and fragments of grains, and 

 with stoppage of the vents, perhaps by sinking 

 of the overlying rocks, would come the ex- 



