Geological magazine . BG. U. Fig. , Cleveland Dyke. O. W. Tyrrell—Alkaline Igneous Rocks, West Scotland. 69 J, J. The line of junction between tachylite and stony rock is perfectly is seen apparently truncating a small felspar on the right-hand side, whilea curved lath is seen just below the contact near the centre of the cracks in the lower layers are not well shown. Fig. 2. Shows a section cut roughly perpendicular to the upper part of Fig. 1. C, C. Cooling cracks, ch. The chlorite fibres bordering them. BG. Dark-brown isotropic glass. Z. Zones of
Geological magazine . BG. U. Fig. , Cleveland Dyke. O. W. Tyrrell—Alkaline Igneous Rocks, West Scotland. 69 J, J. The line of junction between tachylite and stony rock is perfectly is seen apparently truncating a small felspar on the right-hand side, whilea curved lath is seen just below the contact near the centre of the cracks in the lower layers are not well shown. Fig. 2. Shows a section cut roughly perpendicular to the upper part of Fig. 1. C, C. Cooling cracks, ch. The chlorite fibres bordering them. BG. Dark-brown isotropic glass. Z. Zones of paler glass. F. Felspars often faultedby cooling cracks. The direction of flow (L, L) is shown by the shapeand parallelism of the black cigar-shaped bubbles (b, b) ; some of theseare apparently hollow, while a yellow variety is shown at X. It is quiteevident that the cooling cracks here (C, C) have no connexion with thedirection of flow; indeed, they are sometimes seen faulting the bubbles. IV.—The Late Palaeozoic
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectgeology, bookyear1864
