. The hollow spherulites of the Yellowstone and Great Britain. II. in spherulite itself was pale pinkish-white in colour, and the interiorof the cavity and part of the wall, as seen on a fractured surface,were granular. Crystals of fayalite were embedded in and on thewalls. The exterior of the spherulite was slightly irregular, a smallblunt tongue projecting out in one place into the surroundingmaterial. This consisted partly of glass, partly of lithoidal flow-bands. The stellate form of the cavity may be best conveyed byimagining that a blunt wedge was thrust outwards from the cavityinto the
. The hollow spherulites of the Yellowstone and Great Britain. II. in spherulite itself was pale pinkish-white in colour, and the interiorof the cavity and part of the wall, as seen on a fractured surface,were granular. Crystals of fayalite were embedded in and on thewalls. The exterior of the spherulite was slightly irregular, a smallblunt tongue projecting out in one place into the surroundingmaterial. This consisted partly of glass, partly of lithoidal flow-bands. The stellate form of the cavity may be best conveyed byimagining that a blunt wedge was thrust outwards from the cavityinto the yielding substance of the spherulite. In one place thewalls met at a right angle. ^ See Iddiiigs, 7th Ann. Kep. Geol. Surv. (1885-86) p. 264, pi. xii,fiffs. 1 & 5. 214 MR. J. PAKKINSON ON THE HOLLOW SPHERULITES [May I9OI, (ii) Cavities with a definite form. — Almond-shaped cavities,frequently elongated till they resemble a rift in the rock ratherthan an ordinary vesicle, are common. Such a rock resembles aseries of plates, 1 inch thick and upwards, im
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