Januaey 3, 1896.] 



SCIENCE. 



11 



Yet other verification was afterwards 

 found through the published accounts of 

 certain small craters in Germany, France 

 and India. In the valley of the Rhine are a 

 number of circular basins, for the most part 

 containing lakes and hence called maars. 

 They are depressed below the level of the 

 surrounding plain, and some of them are 

 surrounded by raised rims. The descrip- 

 tions are somewhat conflicting, but it is 

 clear that some of the basins are hollowed 

 chiefly from non-volcanic rocks, limestone, 

 sandstone and slate, and that their rims are 

 composed in part of fragments of similar 

 rocks.* The Indian crater (Plate 1 , Fig. 1 ) , 

 which also contains a lake, is hoUowed from 

 a volcanic rock, the Deccan trap, and shows 

 no other material ; but in other features it 

 parallels so closely the Arizona crater that 

 I quote from Doctor Blanford's description: 



" The surrounding country for hundreds 

 of miles consists entirely of Deccan trap ; 

 in this rock, at Lonar, there is a nearly cir- 

 cular hollow about 300 to 400 feet deep, and 

 rather more than a mile in diameter, con- 

 taining at the bottom a shallow lake of 

 salt water without any outlet. * * * * 

 The sides of the hollow to the north and 

 northeast are absolutely level with the sur- 

 rounding country, whilst in all other di- 

 rections there is a raised rim, never ex- 

 ceeding 100 feet in height, and frequently 

 only 40 or 50, composed of blocks of basalt, 

 irregularly piled, and precisely similar to 

 the rock exposed on the sides of the hollow. 

 The dip of the surrounding traps is away 

 from the hollow, but very low. 



" It is impossible to ascribe this hollow to 

 any other cause than volcanic explosion, "f 



* Volcanos. By G. Poulett Sorope. London, 1872. 

 Pp. 369-384. Die Vulkane der Eifel, in ihrer Bild- 

 ungsweise eriautert. By Dr. Herman Vogelsang. 

 Naturkundige Yerhandelingen von der hollandisclie 

 Maalsohappij der Wetenschappen te Haarlem. Vol. 

 21, Part 1. Pp. 41-76. 



fA Manual of the Geology of India, by H. B, 

 Medlicott and W. T. Blanford. Part I., pp. 379-380 

 Svo. Calcutta, 1879. 



For the sake of completeness, mention 

 should be made of two other hypotheses, 

 which resemble the laccolitic suggestion in 

 that each was based on a single feature 

 of the crater but failed to find verification 

 in any other feature. The fact that the pit 

 occurs in limestone suggested that it might 

 be what is called a limestone sink, a cavern 

 having been made by the solution of the rock 

 and the roof having afterwards fallen in.* 

 The fact that the loose debris of the rim lies 

 in hummocks with intervening hollows, and 

 thus resembles in its topographic character 

 the terminal moraine of a glacier, suggested 

 that ice was concerned in its distribution. 



Yet another hypothesis, and the last that 

 need be mentioned, was made by welding 

 together two which had preceded. It is a 

 general fact that causes are complex, and 

 as the explanations which first suggest 

 themselves are apt to be simple, it often oc- 

 curs that the theory finally adopted com- 

 bines elements of two or more of the 

 theories tentatively proposed. The expert 

 constructor of theories is therefore prone to 

 suspect that rival explanations embody half 

 truths, and to seek for methods of combina- 

 tion. The combination proposed in this 

 case utilizes the theory of meteoric impact 

 and the theory of volcanic explosion, and 

 its author is Mr. Warren Upham . His sug- 

 gestion is that, by some volcanic process, 

 heat had been engendered among the rocks 

 of the locality, so that the conditions were 

 ripe for an explosion, and that the mine 

 was actually fired by a falling star, whose 

 collision ruptured a barrier between water 

 and hot rock, or in some other way 

 touched the volcanic button. f It will be 

 noted that this explanation demands a 

 coincidence of what maj^ be called the sec- 

 ond order, for the colliding star is supposed 

 not only to have chanced upon the prepared 



* This suggestion was made by a correspondent, 

 t American Geologist, "Vol. 13, (1894), p. 116; also 

 a personal letter. . 



