academy 0F sciences] SCIENTIFIC ACTIVITIES 183 



No. 0] 



THE ORIGIN OF COON BUTTE 



In point of time the field study of Coon Butte, a curious circular rim around a basinlike 

 cavity in Arizona, preceded and may have suggested the telescopic study of the moon, the 

 beginning of which was alluded to in the preceding section, and the completion of which is told 

 in the next section; but the theoretical discussion of Coon Butte was not published for three 

 years after the appearance of the final essay on the "Moon's face." A possible origin of Coon 

 Butte is indicated by the question-begging name, Meteor crater, by which the cavity within the 

 butte rim had come to be known; and the idea that the cavity marked the place where a huge 

 meteor has embedded itself in the earth's crust presumably had to do with the hypothesis of 

 moonlets embedding themselves in the face of the moon, as the next section will explain. In 

 any case, Gilbert took leave of absence from survey duties in November, 1891, and, with Marcus 

 Baker as aid in the preparation of a topographic and magnetic survey, went to Arizona to ex- 

 amine the crateriform cavity. Several weeks were spent there, and a following fortnight was 

 given to the study of unquestionable volcanic cones and craters in the neighborhood of the 

 great dissected volcano of San Francisco Mountain. Gilbert took along on this excursion 

 the manuscript of a bulky survey memoir on a subject not at all Gilbertian with the intention 

 of giving bad-weather days to its revision; but fortunately the weather was persistently clear 

 and his leave of absence was little interrupted by this office duty. 



Before setting out from Washington, the object of the journey was told in a personal letter: 



The errand is a peculiar one; I am going to hunt a star. . . . Numerous fragments of meteoric iron have 

 been found in a tract adjacent to a "crater," and the crater differs from others in that it is composed of sandstone 

 and limestone and has no volcanic rock. Suspecting that it is the scar produced by the collision of the earth 

 with a small star, Tasked Mr. [W. D.] Johnson to take a look at it, and report. He has done so and his report 

 confirms my suspicions. The scar is % of a mile across and the indications are that the missile is somewhere 

 under the scar. 



But in spite of the provisional acceptance of this meteoric theory, it was given up after the 

 ground was examined. Another letter to the same correspondent tells the story: 



I didn't find the star of course, because she is not there — but like the peasant who subsoiled for gold I reaped 

 a crop that is worth having. Thirty days in camp gave a fine foundation for winter work, and then even though 

 the hole is starless it is probably unique. The theory at present in favor is that hot lava was injected 1200 or 

 1500 feet below the surface of the plain, superheating some water it found there and causing a big blast of steam 

 power. If that theory is good, the shower of meteoric iron was subsequent, and its coincidence in place was 

 fortuitous. . . . Our wagon carried three barrels of water and only one camp was made near a spring. We 

 were free to stop where we pleased, and we always stopped where there was plenty of fueL So we didn't mind if 

 we had to comb ice from our hair after morning ablutions. 



The same subterranean cause of the cavity was given preference two months later, after 

 all other hypotheses had been eliminated; the opinion then expressed was that all the features 

 of the cavity confirmed the view that it was "not produced by the penetration of a large meteor. 

 It is probably due to the explosion of steam caused by the [subterranean] injection of volcanic 

 rocks." As such it was regarded as a first phase in the formation of a volcano; a phase that is 

 ordinarily concealed by the eruptions of the later phases, but which is here visible because no 

 later phases occurred. 



The problem of Coon Butte, as Gilbert called it, was repeatedly the subject of communica- 

 tions at scientific meetings or of lectures before more popular gatherings for several years. It 

 was presented to the National Geographic Society of Washington in March, to the National 

 Academy of Sciences also in Washington in April, and to the American Association at Rochester 

 in August, all in 1892; and in 1S95 at Kansas, Chicago, and Cornell Universities; but in the 

 present connection the problem is chiefly interesting as the subject of a presidential address 

 before the Geological Society of Washington in December, 1895, entitled " The origin of hypoth- 

 eses," ' in which philosophical impartiality in the presentation of alternative hypotheses is 

 illustrated to perfection. A reader of this notable deliverance might indeed contend with good 

 reason that its author seemed more interested in the abstract discussion of his problem than in 



i The origin of hypotheses, illustrated by the study of a topographic problem. Published by the Geological Society of Washington, 1896; also 

 in Science, 111, 1896, 1-13. 



