THE CHONDRITIC STEUCTURE. Ill 



each spherule and the adjacent matrix, as is the case with terrestrial rocks 

 so organized. Such a rehition does not appear to exist, except rarely in 

 meteorites, but the chondri usually pass into the adjacent matrix the same 

 as the secretions formed ])y a cooled lava do into the surrounding magma. 

 So, too, we find diflerent materials mixed in terrestrial tufiis ; and since dif- 

 ferent kinds of rock fall in meteorites, these supposed meteoric tufas, if of 

 mechanical origin, ought to contain all these different forms, instead of only 

 the same material as the groundmass. 



As stated previously, it seems to me, from microscopic study of these 

 structures, that they do not show any evidence of fragmental origin, but 

 they show rather that they have been produced by rapid and arrested crys- 

 tallization in a molten mass; the result being in part due to the forms 

 which the olivine and enstatite tend to assume on crystallization. If time 

 enough had been given, an entire crystallization of the material would 

 have taken place, as in the Estherville peridotite, and in the common ter- 

 restrial peridotites. Of the latter, the crystallization is either complete, 

 or else the original structure has been obliterated by alteration. If we 

 could find rapidly cooled, unaltered terrestrial peridotic rocks, I should 

 expect to find in them the chondritic structure, the same as the Esther- 

 ville meteorite possesses the structure of an unaltered terrestrial peridotite, 

 and the meteoric pallasites possess that of the terrestrial ones. 



A similar method of crystallization, with the production of a similar struc- 

 ture, has been observed by me in the crystallization of watery vapor on the 

 windows of horse-cars during extremely cold weather. When the window is 

 imtouched the crystallization is after the usual manner, familiar to all as 

 occurring in our houses ; but when the car-window has had this first deposit 

 removed, as is frequently done by passengers, for the purpose of looking 

 out, the abundant vapor of the crowded car is rapidly deposited on this cold 

 surface, and in such abundance as to give rise to similar elliptical and spheru- 

 litic figures, which in form and appearance resemble the chondritic forms the 

 more closely the more they interfere with the development of one another. 

 They also possess the eccentric-fan and ribbed structure so commonly seen 

 in the enstatite chondri — the radiation starting from one side. Again, on 

 interfering with one another, they tend to take a rounded, instead of an 

 antjTular or irregular form. 



That rounded, drop-like masses should be inclosed in meteorites is natu- 

 rally to be expected, in case they came from the sun or any similar body, for 



