128 Transactions. 



and a little a?gerine more or less intergrown with the hornblende. 

 The liine-soda feldspar is 'abradorite. A micro-chemical and 

 staining test for nepheline was made without any results. 



28, 51, 76. These are also fine-textured intermediate rocks, 

 with very subordinate feldspar, and ultra-basic in composition. 

 Microscopically, they bear a strong resemblance to Brogger's 

 farrisite, but a chemical test failed to discover the presence 

 of mellilite. The feldspar is partly anorthoclase, and the balance 

 a basic plagioclase with the extinction angle of bytownite. 

 28 contains pseudomorphs of serpentine after augite, with 

 occasional cores of the original mineral remaining. The horn- 

 blende occurs in two generations, with sharply idiomorphic 

 outlines. 51 has, in addition to a sprinkling of magnetite dust, 

 some plates of pyrite, probably of secondary origin. In 76 the 

 augites are fresh, but these are serpentinous pseudomorphs 

 after olivine. Without the accessory feldspar the rocks would 

 be monchiquites, which they most nearly resemble. (Plate 



XVIII, fig. 5.) 



100. Camptonite. The hornblendes differ from those in the 

 vogesites and some of the transitional rocks in that, although 

 preserving the same sharpness of outline, they do not tend 

 to assume the elongated and belemnitic forms. The augite 

 is partly serpentinised, and is subordinate to the hornblende, 

 which constitutes nearly one-half of the rock. Borders of 

 segerine surround some of the hornblende phenocrysts, and 

 small independent crystals of segerine are present. The feldspar 

 is labradorite, with a maximum extinction-angle of 32°. (Plate 



XIX, fig. 13.) 



40, 82, 84, 97. Diabase and olivine-diabase. In the group 

 represented by these sections the hornblende has almost dis- 

 appeared, and only occurs as small granules, whilst the crystal- 

 lization of the feldspar has preceded that of the ferro-magnesian 

 minerals in the groundmass. The feldspar labradorite is in 

 columnar crystals, with an occasional rectangular plate, but 

 without law of arrangement. The augite, partially serpentin- 

 ised, is in small grains, without definite shape, and interstitial 

 to the feldspar. In some of these rocks there is a recur- 

 rence of the augite, which appears as phenocrysts. Olivine is 

 frequently present, partly serpentinised, but generally with 

 good kernels of fresh mineral surrounded by serpentine, and 

 this again by a thin margin of finely granular magnetite, which 

 gives the outline of the original crystal, and shows that before 

 alteration the olivine possessed good crystal forms. In some of 

 the sections there is a little isotropic matter. These rocks are 

 classified as diabase and olivine-diabase according to whether 

 the niagnesian mineral is absent or present : hut some of them, 



