Januaey 3, 1896.] 



SCIENCE. 



of direction, or the inclination of the dip 

 needle ; and the intensity of the magnetic 

 force. Two lines of stations, at right angles 

 to each other, were carried across the crater, 

 and one of these lines was extended to a 

 distance of three and a half miles on the 

 plain. When the results were tabulated and 

 compared, the magnetism was found to be 

 constant in direction and intensity at all the 

 stations, the deviations from uniformity be- 

 ing not greater than the unavoidable errors 

 of observation. So if the crater contains a 

 mass of iron its attraction is too feeble to 

 be detected by the instruments employed. 

 That we might learn the precise meaning of 

 this result, the delicacy of the instruments 

 was afterward tested at the Washington 

 Navy Yard, by observing- their behavior 

 when placed in certain definite relations to 

 a group of iron cannon whose weight was 

 known, and the following conclusions were 

 reached : If a mass of iron ecxuivalent to a 

 sphere 1500 feet in diameter is buried be- 

 neath the crater it must lie at least 50 

 miles below the surface ; if a mass 500 feet 

 in diameter lies there its depth is not less 

 than 10 miles. So the theory of a great 

 iron meteor is negatived by the magnetic 

 results, unless we may suppose either that 

 the meteor was quite small as compared to 

 the diameter of the crater, or that it pene- 

 trated to a very great depth. 



The topographic survey was executed 

 with such detail as to warrant the drawing 

 of contour lines for each ten feet of height. 

 (Plate 1, Fig. 3.) During its progress the 

 configuration of the surrounding country 

 was carefully studied, and its general plan 

 was found to be so simple and regular that 

 the original contours before the creation of 

 the crater could be restored without great 

 liability of error. (Plate 1, Fig. 4.) Such 

 restoration was made, and with its aid two 

 quantities were afterwards computed: first, 

 the cubic contents of the rim so far as it 

 projects above the ancient surface ; second, 



the cubic contents of the hollow so far as it 

 lies below the ancient surface. The two 

 volumes were compared with each other 

 and also with the volume of a spherical pro- 

 jectile estimated as competent to produce 

 the crater. From experiments with balls 

 of clajr fired against a target of the same 

 material it seems probable that a crater 

 4,000 feet in diameter might be produced 

 by a swift-moving meteor with a diameter 

 of 1,500 feet. (Plate 1, Fig. 6.) It seems 

 possible, though not probable, that it could 

 be made by a mass 750 feet in diameter. 

 The volume of the greater assumed pro- 

 jectile is 60 million cubic yards ; the vol- 

 ume of the lesser, 7^ million yards. The 

 magnitude of the hollow was found to be 

 82 million yards, and the magnitude of the 

 rim was also found to be 82 million yards. 

 It, therefore, appears that if the rim were 

 to be dug away down to the level of the an- 

 cient plain, and the material tightly packed 

 within the hollow of the crater, it would 

 suflice to precisely fill that hollow and re- 

 store the ancient plain. The excess of mat- 

 ter required by the theory of a buried star 

 was not found. 



Thus each of the two experiments whose 

 testimony had been invoked declared against 

 the theory of a colliding meteor ; and the 

 expectation founded on the high improba- 

 bility of fortuitous coincidence nevertheless 

 failed of realization. 



Attention being now directed to the only 

 surviving theorj^, that of steam explosion, 

 all the various features discovered in the 

 local study were considered with reference to 

 it. To describe and discuss them on this oc- 

 casion would lead too far from our subject, 

 and they may be passed by with the remark 

 that, while not all are as yet fully under- 

 stood, they seem not to oppose the theory. 



For the sake of applying another quanti- 

 tative test, an attempt was made to ascer- 

 tain whether the energy which could be de- 

 veloped by heating the water contained in 



