883 W. CAMPBELL SMITH. 



litic') basalt from Skye," described in 1899 by Messrs. 

 Clough and Harker^ affords a very close parallel to some of 

 the phenomena mentioned above. This rock occurs as 

 a sill of Tertiary age at Camas Daraich, Point of Sleat, 

 Skye. The spherulites vary in diameter from 1^ to 3 inches, 

 and occur throughout the entire sheet. Sections show that 

 some parts of the rock contain some residual glass, but this 

 is usually absent, and then, but for the presence of olivine in 

 place of the augite phenocrysts, the two rocks are wonder- 

 fully similar in structure. The similarity is also evinced by 

 the presence of minute ophitic plates of augite and by small 

 extinction-angles in the felspars, the latter phenomenon being- 

 attributed to overlapping of the fibres. 



Another somewhat similar case of spherulitic structure in 

 dolerite has been described by Schwantke'"^ in a rock from 

 OHeiden, Taunus Mts., where it is associated with typical 

 variolites. It is interesting to note that in parts of this rock 

 there is a micrographic intergrowth of augite and felspar. 



A very interesting occurrence is also described by E. B. 

 Bailey^ from Ardmuclmish, Argyllshire. The spherulites are 

 small and lie in a ground-mass which is to a large extent 

 glassy, but their structure is very similar to that of the 

 Vryheid rock. Among other interesting points he records 

 the presence of negative crystals in the felspars filled with 

 glass and iron oxides, and he shows that the augite and 

 felspar crystallised almost simultaneously, though the felspar 

 seems to have commenced first. 



This intimacy of growth between the augite and felspar is 

 very striking, as it is observed in every one of these four 

 cases. It is no doubt an expression of the fact that in each 

 case the spherulites have ci"ystallised out of a magma which 

 approximated to the eutectic composition. In acid rocks 



• Cloug-h and Htirker, ' Tmns. Edinburgh Geol. Soc.,' vii (1898), 

 p. 381. 



2 A. Schwautke, ' Nenes Jahrb. f. Min., etc..' Beil.-Band xviii. (1903). 

 p. 503. 



'' E. B. Bailey, 'Trans. Edinbin-gh Geol. Soc' viii. (1904), p. 363. 



