140 Trans. Acad. Sci. of St. Louis. 
true. The dry climate, and the constant removal of the 
lighter soils by the winds,?’ 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,?* Tolman,”® and others,®° 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,*' 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®? 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 
*% Bull. Geol. Soc. Amer. 19:73. 1908. 
Trans. Amer. Inst. Mining Eng. 34:161. 1904. 
*? Journ. Geol. 17:149. 1909. 
* Bull. Geol. Soc. Amer. 19:74. 1908. 
%1 Carnegie Inst. Yearbook, 3:208. 1905. 
2 Beitrage zur Mechanik des Himmels, 157. 1848. 
