January 3, 1896.] 



SCIENCE. 



was so attractive that I desired to visit the 

 crater, but as that was not immediately 

 practicable I arranged to have it visited by 

 one of my colleagues. A few months later 

 Mr. Willard D. Johnson spent several days 

 at the locality, making a sketch map and 

 describing the various features. When he 

 reached the rim of the crater he found it to 

 consist chiefly of limestone strata inclined 

 outward, and his first thought was that the 

 rim might be the remnant of the dome of 

 strata over a laccolite. The laccolite is a 

 peculiar volcanic product. The molten 

 lavas which make volcanoes rise from deep 

 sources through cracks or passages among 

 the rocks and flow out over the surface of 

 the land ; but sometimes rising lavas fail to 

 reach the surface, and accumulate at lower 

 levels, opening for themselves bubble-shaped 

 chainbers over which the strata are arched. 

 In the dome-like structures thus produced 

 the rocks dip outward in all directions from 

 a central region, and this outward dip was 

 the feature which, through analogy, sug- 

 gested to Mr. Johnson a laccolitic origin. 

 His first idea, however, was not long 

 retained, for examining the walls and bot- 

 tom of the ci'ater he found no trace of 

 the igneous rocks of which laccolites are 

 composed, and the theory afforded no 

 aid in accounting for the hollow. He there- 

 fore dismissed it and sought another. He 

 may have considered several others, but 

 the only one placed on record is an explosion 

 theorj\ In some way, probably by vol- 

 canic heat, a bodj^ of steam was produced 

 at a depth of some hundreds or thous- 

 ands of feet, and the explosion of this 

 steam produced the crater. The fall of 

 iron was independent, and the associa- 

 tion of the two occurrences in the same 

 locality is accidental.* As Mr. Johnson is 

 at once a civil engineer and a student of 

 geology and geography, he had at command 



"•■ Mr. Johnson's discussion of the problem was 

 communicated to me in a personal letter. G. K. G. 



as basis for analogic reasoning the explo- 

 sive phenomena associated with the arts and 

 also those which belong to the history of 

 volcanoes, and we may assume that these 

 suggested his theory. 



Mr. Johnson's account of the crater 

 was much fuller than Dr. Foote's, but in- 

 stead of satisfj'ing my curiosity tended 

 rather to whet it, and I availed myself of 

 the first opportunity to make a personal 

 visit. Four hypotheses had now been 

 made, but only two survived. The theory 

 of the shepherds, deriving the iron from the 

 cavity of the crater, was disproved by Dr. 

 Foote's determination of the meteoric 

 character of the iron. The laccolitic theory 

 had been promptly set aside by Mr. John- 

 son. There remained the theory of a star's 

 collision and the theory of a steam ex- 

 plosion. If my visit was to aid in the de- 

 termination of the problem of cause it 

 must gather the data which would discrimi- 

 nate between these two theories, and an 

 attempt was accordingly made to devise 

 crucial tests. If the crater was produced 

 by the collision and penetration of a stellar 

 body that body now lay beneath the bowl, 

 but not so if the crater resulted from ex- 

 plosion. Any observation which would 

 determine the presence or absence of a 

 buried star might therefore serve as a cru- 

 cial test. Direct exploration by means of a 

 shaft or drill hole could not be undertaken 

 on account of the expense, but two indirect 

 methods seemed feasible. 



If the crater were produced by explosion 

 the material contained in the rim, being 

 identical with that removed from the hol- 

 low, is of equal amount; but if a star 

 entered the hole the hole was partly filled 

 thereby, and the remaining hollow must be 

 less in volume than the rim. The presence 

 or absence of the star might therefore be 

 tested by measuring the cubic contents of 

 the hollow and of the rim and comparing 

 the two. Of the intellectual origin of this 



