THE RICHARDTON METEORITE 447 



Although after explosion it seems that the meteorite was not 

 incandescent, it certainly was fused additionally; for all the 

 surfaces freshly exposed by the main disruption were completely 

 fused over by the time the fragments reached the earth. To such 

 an extent was that accomplished that it is not quite certain to 

 the writer that all the material discovered entered the atmosphere 

 as parts of a single mass. Many of the smaller pieces, particularly, 

 appear as if they may be units of a shower. Among the smallest 

 pieces certain specimens show clearly three degrees of fusion. 

 All the specimens from the northern part of the locality are covered 

 with a thick, well-fused crust. Only the small pieces from the 

 southern part of the area have slightly fused surfaces. These 

 small pieces went through at least 5 miles less of the atmos- 

 phere than the thoroughly fused pieces, and some of them, at least, 

 are fragments of a second disruption which must have occurred 

 very near the earth. Presumably the small pieces fell first because 

 they offer more areal resistance to the atmosphere per unit mass 

 than the larger pieces. 



Unquestionably atmospheric obstruction is responsible for the 

 fusion and disruption of the meteorite. Disruption is commonly 

 ascribed to shock of impact with the air, and to the disruptive 

 effect of heat. The heat, however, probably penetrates a very 

 little distance beyond the crust of actual fusion and combustion, 

 and the character of meteorite ruptures certainly is not like that 

 due to the spalling of heated surficial masses. In most cases 

 meteorites are broken through the main mass, rather than shelled 

 off in the familiar manner of insolation spalling of massive rocks. 

 In the case of the Richardton meteorite, rupture was facilitated 

 in places by the presence of metallic and troilite veins, which are 

 planes of weakness. Several specimens are bounded partly by 

 more or less fused metallic vein matter. 



The question arises as to why the light of the meteorite ceased 

 with its disruption. The disruption of the meteorite is described 

 as an explosion, but this is probably a poor choice of words. There 

 is apparently nothing in the meteorite capable of causing an 

 explosion; but if it had exploded, part of the mass would have 

 continued at a higher velocity relative to the air and part at a 

 speed less than that previous to its explosion. The fact is that 



