The Quarterly journal of the Geological Society of London . shown in PL XXXVIII, fig. 3,exhibits pleonaste-grains with a pink mineral—garnet—surroundingthem. Biotite is also present, while the ground-mass is composed ofbasic felspar and cordierite. 2. Hornblende-andesine rock, Ladysmith, magnified 30 diameters. Com- posed of a plate of brown hornblende, poecilitically enclosing grainsof andesine. (See p. 281.) 3. Cordierite-norite from Ladysmith, magnified 100 diameters, ordinary light. Shows vermicular garnet surrounding pleonaste and grains offelspar. (See p. 291.) Plate XL. Geological map o
The Quarterly journal of the Geological Society of London . shown in PL XXXVIII, fig. 3,exhibits pleonaste-grains with a pink mineral—garnet—surroundingthem. Biotite is also present, while the ground-mass is composed ofbasic felspar and cordierite. 2. Hornblende-andesine rock, Ladysmith, magnified 30 diameters. Com- posed of a plate of brown hornblende, poecilitically enclosing grainsof andesine. (See p. 281.) 3. Cordierite-norite from Ladysmith, magnified 100 diameters, ordinary light. Shows vermicular garnet surrounding pleonaste and grains offelspar. (See p. 291.) Plate XL. Geological map of the neighbourhood of Huntly, on the scaleof 1 inch to the mile, or 1 : 63,360. Discussion. Dr. J. V. Elsden drew attention to the great complexity ofthe area described by the Author, and to its importance from apetrographical point of view. There appeared to be in thepaper evidence bearing upon magmatic differentiation, marginaldifferentiation, and composite intrusions. With regard to the last- Quart. Journ. Geol. Soc. Vol. LXX, 1. *.30. 2. x 30
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
