140 Trans. Acad. Sci. of St. Louis. 



true. The dry climate, and the constant removal of the 

 lighter soils by the winds, 27 tend to keep all pebbles and 

 larger rock-fragments continually exposed on the surface 

 of the ground. The pebble-mosaics, such as are described 

 by Blake, 2S Tolman, 29 and others, 30 covering large tracts 

 of arid plain amply attest the extent of this remarkable 

 phenomenon. 



These are some of the reasons for observing that the 

 great abundance of meteoric falls in the Canyon Diablo 

 district does not appear to be unique but is really a gen- 

 eral desert phenomenon. 



Bearing of the Planetesimal Hypothesis. 



It follows from a consideration of the plantesimal the- 

 ory of the earth's origin, as recently and specifically set 

 forth by Professor Chamberlain, 31 that there should be 

 falling upon the surface of our planet a constant rain of 

 rock-forming materials derived directly from extra-ter- 

 restrial sources. That such a shower actually takes 

 place seems now fully demonstrated by a number of facts. 

 That it is an important general source of ore materials 

 appears also sufficiently substantiated. 



The meteoritic theory is not a new one. So long ago 

 as 1848, Meyer 32 presented a well supported hypothesis 

 of an origin of the planetary and stellar bodies, through 

 meteoric agglomeration. Since the first appearance of 

 the astute German author's work the theory has had the 

 hearty support of many able thinkers. 



That portion of the stellar dust which falls into the 

 sea goes to form the characteristic bottom-muds of the 

 ocean. Another part which falls upon the moister land 

 areas mingles immediately and almost unnoticed with 



= 7 Bull. Geol. Soc. Amer. 19:73. 1908. 



28 Trans. Amer. Inst. Mining Eng. 34:161. 1904. 



29 Journ. Geol. 17:149. 1909. 



30 Bull. Geol. Soc. Amer. 19:74. 1908. 



"Carnegie Inst. Yearbook, 3:208. 1905. 



M Beitrage zur Mechanik des Himmels, 157. 1848. 



