structures in Stony Meteorites. 63 



element has for a like substance, requires time in which to act. 

 As its period of action is of necessity confined to the molten 

 condition of the mass, larger nodules would result during a 

 protracted cooling than where solidification occurs more 

 rapidly. The principle applies to meteorites. The degree of 

 crystallization bears the same relation to time. When rocks 

 become solidified beneath the surface, where the temperature is 

 much higher than that of the atmosphere, the crystalline struc- 

 ture is well defined and marked, due to the slowness of solidi- 

 fication ; whereas if solidification takes place after eruption, 

 the crystalline structure is not perceptible, due to rapid solidi- 

 fication. 



It is probably true that when iron meteorites enter our 

 atmosphere, they are frequently associated with the stony 

 magma in which they were formed, and the atmospheric resist- 

 ance causing the mass to explode, would tend to separate this 

 magma along planes of the nodular masses of iron, which, 

 owing to their greater specific gravity, would reach the sur- 

 face of the earth at a different time and place from their 

 accompanying matrix. 



The Estherville meteorite, which fell May 10th, 1879, is a 

 case in point. A number of months after the fall and some 

 four miles distant, were found over five thousand nodules of 

 iron, ranging in size from a pea to a pound in weight. Now 

 these are known positively to be portions of the Estherville 

 meteorite, not only by their resemblance to similar masses 

 found in the meteorite, but from the fact that a number of 

 boys herding cattle near a pond, at the time the meteorite 

 passed over them, saw a great shower of what appeared to be 

 hailstones fall. They state that the surface of the water was 

 alive with the falling bodies. 



Therefore, if the larger masses of iron could occur only 

 when the process of solidification was most abnormally slow, 

 we would expect that the majority of meteorites reaching us 

 would be those that contained but small nodules or specks of 

 iron. 



It seems probable that certain of the stony meteorites that 

 have been found are really the matrices in which some of the 

 iron nodules, found perhaps many miles distant, were embed- 

 ded at the moment they entered our atmosphere. 



Another distinct and most important point is that the 

 rougher the exterior surface of an iron meteorite, and the 

 deeper and larger its pittings, the more marked is its crystal- 

 line structure, and the greater the number and the larger the 

 size of the troilite nodules, as disclosed by slicing and etching. 

 On the contrary, if the exterior surface is comparatively 

 smooth, on slicing and etching, we find the Widmanstatten 



