THE METEORIC PERIDOTITES. — SAXONITE. 87 



the writer believes, resides the cause of the peculiar structure of the chondritic meteor- 

 ites, while, if through any cause the mass cools more slowly, the result is to unite the 

 detached grains into larger crystals, as in the Estherville meteorite and in the ordinary 

 terrestrial peridotites. These structures, certainly, do not vary any more from one 

 another than do the glassy, the glassy and globuhtic, and the crystalline forms of basalt. 



The base in this peridotite varies from a light to a dark ash-gray, and is fibrous-gran- 

 ular in its structure. The darker shades are generally associated with the olivine and 

 the lighter with the enstatite. Various gradations are seen between that state of the 

 base which does not affect polarized light, and that which shows feeble coloration — 

 properly not a base. These gradations are owing to the dilierentiatiou in it of more or 

 less granules of olivine or enstatite, causing the depolarization of the light. The feeble 

 polarization ajipears to be owing to a differentiation of the base so as to leave but mi- 

 nute portions of it iu the original state, although the difference between the two states is 

 not noticeable in common light. The tendency of these granules is to unite into a homo- 

 geneous crystal, the base disappearmg more and more, according to the conditions attend- 

 ing the solidification of the mass. Furthermore, as in other rocks, so in this, the base 

 should be expected to be one of the first materials, after the ii'on, to suffer alteration. 

 The writer supposes this base to be that whicli other writers have described as the 

 matrix of fine dust, formed by the comminution of the meteoric material, — flocculent, 

 opaque, white mineral ; * also as felspathic material, etc. 



A series of grains and crystals of olivine, arranged in splierical form and cemented 

 by i\\Q fihroHS-fjranular base, forms the olivine chondri. I do not regard these as rounded 

 forms, owing their shape to mechanical action, for no abrupt line separates them from 

 the surrounding material, as is the case when detached fragments are inclosed in a 

 matrLx. In the same way the gi'anules themselves show that they are products of crys- 

 tallization, and not broken fragments held in- the matri.x. As said before, I can see no 

 structure, in this or in any of the other meteorites examined, supporting the mechanical 

 theory of their origin ; but everything observed, in my judgment, points to crystalliza- 

 tion in a more or less rapidly cooling body. In some instances it is, indeed, true that an 

 abrupt termination exists to some of the forms, but these appear to be fragments of 

 base, sometimes' partly differentiated, caught m the liquid mass, instead of mechanical 

 forms torn from some previously existing rock. 



This meteorite has also been described by Lasaulx, who states that it shows an evi- 

 dent brecciated structure, with olivine grains and rounded enstatite masses, in a fine- 

 grained groundmass, containmg grains and fragments of crystals, as well as iron and 

 pp-rhotite. Plagioclase is said to be present, and the base is described as a gray, fine- 

 grained, aggregate, cementing mass, resembhng the granular microfelsitic groundmass 

 of many porphyries. f 



Figure 4, Plate II., shows well the finer-grained portions of this meteorite with 

 the native u'on. The portion to the left of the centre represents one of the chondri, 

 composed of detached gi'aius held in a dark base. The grains are found to be divided by 

 polarized light mto three sets, one of which occupies the lower portion and tlie other two 

 the upper portion of the chondrus. The grams m each division act optically as a unit, 

 and cause the chondrus to present the appearance of a crystal composed of three 

 twinned portions ; and it is here thought that had not the crystallization been arrested, 



* Maskehne, Pliil. Mag , 1S63 (4), xxvi. l:5S. 

 t Sitz. niedcr. Gcsclls. Bomi, 18b2, pp. 102-103. 



