676 



SCIENCE 



[Vol. LV, No. 1434 



experience in such matters. He was sitting in 

 front of a house occupying a somewhat ele- 

 vated position with reference to the rest of 

 the town. Suddenly a meteorite appeared 

 descending from the sky, and fell, he was sure, 

 within a certain square on the lower level. He 

 at once proceeded to the spot, only to find that 

 he was mistaken but that it had fallen a "few 

 blocks away." At this second point the same 

 experience was repeated, and the stone finally 

 located some twenty miles beyond the point 

 where he was "certain" he had seen it strike. 



An equally good illustration was offered in 

 the flight of a meteorite over the city of Wash- 

 ington on Sunday, January 12, 1919. This 

 was first called to my attention by a man some 

 eighty miles south of Washington who saw it, 

 as he assured me, strike the ground within one 

 half a mile of where he was standing. Inas- 

 much as the meteorite had been observed pass- 

 ing over Washington in a northeasterly direc- 

 tion his statement was not accepted. Further 

 reports of the fall in the immediate vicinity of 

 the city and a few miles away were also re- 

 ceived. Taking the direction along which the 

 meteorite was traveling, I followed it up by 

 correspondence for a distance of over 300 miles 

 into northeast Pennsylvania where it became 

 lost. The last reports received indicate that it 

 was going in two directions at once ( ! ) and it 

 is very probable that it actually fell somewhere 

 in that vicinity, nearly 400 miles from where 

 first seen to fall. 



Experiences similar to the above are com- 

 mon. In many other instances stones which 

 were "seen to fall" have proved to be of strictly 

 terrestrial origin. There comes a sudden flash 

 and report, the obsei-ver goes quickly to the 

 spot and there finding an object which had not 

 previously attracted attention, assumes it to be 

 a meteorite and in perfectly good faith writes 

 some museum announcing his discovery and 

 willingness to dispose of the same. There is 

 probably not a museum of importance in the 

 world that does not annually receive from one 

 to many announcements of this kind. The re- 

 ceipt even of glacial boulders which were 

 "warm when picked up" or "which set &re to 

 the grass at the point where they feU" is not 

 unusual. 



This leads to the second point to which 

 attention need be directed — that relating to the 

 reported temperature of the fallen body, which 

 is often to the effect that "it was too hot to 

 touch," or has been the cause of fires. As in 

 a great majority of cases it is impossible to 

 investigate the actual temperature after the 

 first report has been made it may be well for 

 the moment to consider the probabilities. 



While the original source from which mete- 

 orites are derived is problematical it yet 

 seems certain that they have been wandering 

 for an indefinite period in space and at a tem- 

 perature of "absolute zero." At the time of 

 entering our atmosphere it is fair to assume 

 they are cold throughout to a degree of which 

 we can have no conception. During the few 

 seconds in which they are passing through our 

 atmosphere, they become intensely heated on 

 the immediate surface, but these portions are 

 immediately stripped off, and, as we have abso- 

 lute proof, the heat never extends to a distance 

 of more than two or three millimeters. Before 

 striking the ground the speed of the body is 

 so far checked that it ceases to glow and the 

 thin film of molten material quickly congeals. 

 Cooling of the surface, owing to the intense cold 

 of the interior, must follow rapidly and it is 

 questionable in the writer's mind if a large ma- 

 jority of the reports of the heated condition of 

 the meteorite when found are not based upon 

 expectation rather than fact. He even goes so 

 far as to suggest that when it shall become real- 

 ized by the public at large that the chances are 

 in favor of a meteoric stone being cold rather 

 than hot when found, it wUl be so reported. 



George P. Merrill 

 U. S. National Museum, 

 Washington, D. C. 



ORIGIN OF SOIL COLLOIDS 



Dr. Whitney^ has advanced an interesting 

 theory as regards the origin of , soil colloids. 

 He says, in part: 



My present view is that particles of matter 

 derived from silicate rocks and other soil-forming 

 minerals when they approach a diameter of .0001 

 mm. contain relatively so few molecules that the 



1 Science, 54: 656, 1S21. 



