176 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



meteorites stich as ai-e tigured by Tschennak| and Wadsworth.;^ 

 Olivine in a similar condition in terrestrial rocks has recently- 

 been described and tigured by Renard in specimens from Kergueleii 

 Islaml in the Indian Ocean. || The polysomatic structure in augite 

 is not so well known. Renard notes that the augites of the feld.s- 

 pathic basalt of Heard Island, Indian Ocean, are grouped together 

 at certain points,** and again in the same rocks in Marion Island that 

 the augite is characterized by a tendency to form groups of individuals 

 having their vertical axes parallel. ff Teall jiientions " Granular 

 Aggregates " of augite in the Hett and the High Grreen dykes in the 

 north of England. 1| Some of these appear from the figures given to 

 be aggregates of grains of augite not in close juxtaposition with an 

 interstitial base, although that tigured in Plate xii. Fig, 5, would 

 seem to be a polysomatic augite, and if so is the only strictly 

 parallel instance that I can find of this structui-e so common in this 

 dyke and in others of the i-egion. 



The augite is generally altered to hornblende at its periphery and 

 occasionally the latter mineral entii'ely replaces the former. The 

 process of alteration does not appear to proceed along the almost 

 or quite imperceptible lines of demaikation between the diffei'ent 

 individuals of the polysomatic augite, but extends from the peri- 

 phery of the mass as a whole in towards its centre. 



The plagioclase appears in two general forms, a rather stout or 

 tabular form which is the larger and usually the more cloudy with 

 decomposition products, and a small long lath shaped leldspar which 

 appears quite fresh and in which the polysynthetic lamellae are much 

 more distinct than in the former. 



Magnetite occurs in ii-regularly bounded masses or is disseminated, 

 often quite thickly, through the augite as inclusions of dusty or 

 finely granular aspect. Pyrite also occurs and is discernable macro- 

 scopically. Apatite is seen in occasionally colorless hexagonal 

 sections and in slender prisms with rounded terminations. Water- 

 clear quartz, with inclusions of apatite microlites and liquid inclusions 



♦ Die Mikr. Beschaflf. der Meteor. Stuttjrart, 18S5, Taf. xv. Fig. 1 and 2. 



§ Litholog-ieal Studies, Mem. Mus. Comp. Zool. Harvard, Vol. x., pi. 1. 



II Notice sur la geologie de 1 ile de Kergueleii, Bui. Mus. Ro}'. Hist. Nat. Telgique, Tome IV. 

 No. 4 , p. 233, fig. 1, pi. V. 



** Notice sur les roches de 1' ile Heard. Bull. Mus. Roy. Hist. Nat. Eelgique, 18S6, 8 p. 260. 

 1 1" Notice sur les roches de 1' ile Marion. Ibid. p. 250. 

 XI Petrographical Notes on some north of England Dykes, Q. J. G. S., 1884, 158. p. 229 and 242 



