146 Trans. Acad. Sci. of St. Louis. 
composed of fine mineral particles and that the particles 
are ‘‘mainly terrestrial’’ he gives no data upon which he 
bases his latter conclusions, and he leaves it to be inferred 
that he regards at least part of the material as meteoritic 
in character. The myriads of dust-wells which the same | 
observer describes** in the surface of the great Iglooda- 
homyn glacier in Greenland seem to have a like signifi- 
cance. 
Metallic Sands of Arid Soils. Important as may be 
such phenomena as are afforded by the larger Canyon 
Diablo falls it is also to the desert regions that it seems 
we must turn for information concerning the rain of . 
stellar dust. The prevalency of black sand-grains in the 
desert soils has generally escaped notice. On the vast 
high plains of the dry Mexican tableland fine metallic 
particles occur abundantly in the soils miles’ removed 
from the mountains, and from outcrops of igneous rocks. 
The plains are so level, the distances so great, and the 
rain-fall so scant, that it precludes the transportation of 
the heavy grains by means of water. The high specific 
gravity of the material must prevent their movement by 
means of the winds. Yet after severe rain showers which 
occur at rare intervals when little rills traverse the plains- 
surface with its relative high gradients quantities of the 
iron sands accumulate along their paths. A thorough 
chemical investigation of the composition of these sands 
would be highly instructive. The better known placer black 
sands which have recently attracted wide attention are to- 
tally distinct; and their origin may usually be directly 
traced to decomposing igneous masses. The metallic sand- 
particles of the desert rocks would long resist decay. 
Should these particles prove to be undoubtedly of meteo- 
ritic origin it would make such estimates of the average 
meteoritic augmentation as those of Chamberlain and Sal- 
isbury*® very inadequate. As it is these figures must be 
vastly too low. 
* Tbid. 215. 
* Geology, 1:381. 1905. 
