176 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



meteoi'ites such as are figured by TschermakJ and Wadsworth.§ 

 Olivine in a similar condition in terrestrial rocks has recently 

 been d(!scribed and figured by Eenard in specimens from Kergnelen 

 Island in the Indian Ocean. 1| The polysomatic structure in augite 

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

 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 characterize 1 by a tendency to form groups of individuals 

 having their vertical axes parallel. ff Teall mentions "Granular 

 Aggregates " of augite in the Hett and the High G-reen dykes in the 

 north of England.! J 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 figured 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 structure so common in this 

 dyke and in others of the region. 



The augite is generally altered to hornblende at its periphery and 

 occasionally the latter mineral entirely replaces the former. The 

 process of alteration does not appear to proceed along the almost 

 or quite imperceptible lines of demarkation between the different 

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

 pheiy 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 pi-oilucts, and a small long lath shaped leldspar which 

 appears quite fresh and in which the polysynthetic lamellae are much 

 more distinct than in the foi-mer. 



Magnetite occurs in irregularly 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 lounded terminations. Water- 

 clear quartz, with inclusions of apatite microlites and liquid inclusions 



t Die Mikr. Beschaff. der Meteor. Stuttgart, 1SS5, Taf . xv. Fig. 1 and 2. 



§ Lithological Studies, Mem. Mus. Comp. Zool. Harvard, Vol. x., pi. 1. 



II Notice sur la geologie deT ilede Kerguelen, Bui. Mus. Roy. Hist. Nat. Belgique, Tome IV. 

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



** Notice sur les roches de 1' He Heard. Bull. Mus. Roy. Hist. Nat. Belgique, 18S6, S p. 260. 

 t (■ Notice sur les roches de 1' He Marion. Ibid. p. 250. 

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



