and bastite, containing enclosures of serpeutinized olivine. They resemble 

 very closely, both macroscopically and microscopically, the serpentine with 

 bastite from Baste (Harz), Kupferberg (Bavaria), and Santa Catarina (Elba). 

 The rock with which the serpentine is immediately associated at Belhelvie 

 is a plagioclase-olivine rock (troctolite), in which the relative proportions of 

 the two principal constituents exhibit a considerable amount of variability ; 

 in some varieties the felspar, in others the olivine is the dominant mineral. 

 Here, as elsewhere, we have evidence of the variability in composition, which 

 is such a constant feature in rock masses of ultra-basic composition. The 

 mother-rock of the serpentine examined by Professor BOXNEY was a saxonite 

 (olivine-enstatite rock). The bastite of the serpentine mass near the Black 

 Dog was isolated and analysed by Dr. HEDDLE. (See ante p. 118.) 



Serpentine occurs at other localities in Aberdeenshire, as for example 

 at Barra Hill, near Old Meldrum, (1) and near the railway station, Rothiemay. 

 It is found also at Polmally in Glen Urquhart, at Killin in Perthshire, at 

 Colafirth Yoe in the mainland of Shetland, and in the outlying islands of 

 Unst and Fetlar, where it occurs in association with diorite and gabbro, as at 

 Portsoy. In the absence, however, of detailed petrographical descriptions 

 of the rocks of these localities it is impossible to give precise details in the 

 present work. 



The serpentines of Connemara, and the Highlands and Western Isles of 

 Scotland, which occur in association with crystalline limestones, will be 

 referred to in connection with the latter rocks. 



Messrs. KING and ROWXEY ( ' 2) mention the occurrence of a serpentine at 

 South Cannaver Island, Lough Corrib, which appears to be formed by the 

 alteration of radiating masses of actinolite or tremolite. They state that 

 their attention was called to this case by Mr. KINAHAN, who has referred to it 

 in the description of Sheet 95 of the Geological Survey of Ireland. 



At Duporth, two miles east of St. Austel, occurs a rock of somewhat 

 remarkable composition w r hich may be referred to in this connection, though it 

 is certainly not a true serpentine. It is remarkably soft and may be readily 

 cut with a knife. It is grey, or greenish grey in colour, on a rough surface, 

 but is capable of taking a good polish, and then one sees pale green spots on a 

 darker groundmass. These spots sometimes show definite crystalline boundaries 

 which suggest that they are pseudomorphs after olivine. Two analyses have 

 been made of somewhat different varieties of this rock; one by Mr. PHILLIPS/^ 

 (I.), the other by Mr. CoLLixs, (4) (II). The analysis of a picrite from 

 Giimbelberg is quoted for comparison (III.) 



(1) Dr. HEDDLE, Trans. Roy. Soc., Edin., vol. XXVIII., p. 554. 



(2) An Old Chapter of the Geological Record, 1881, p. 39. 



(3) On the so-called Greenstones of Central and Eastern Cornwall. Q.J.G.S., Vol. XXXIV., 

 1878, p. 474. 



(4) On the Serpentine of Duporth, in St. Austel's Bay, Cornwall. British Association 

 Report for 1877. 



