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 44 in the surface of the great Igiooda- 

 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 45 very inadequate. As it is these figures must be 

 vastly too low. 



"IMd. 215. 



"Geology, 1:381. 1905. 



