On the Igneous Rocks associated with the Cambrian Beds of the Malvern Hills

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Abstract
I. Historical Summary The crystalline core of the Malvern Hills was at first supposed by Horner 1 to be composed of igneous rocks intruded into the adjacent strata. Murchison at a later date imagined that the Hollybush Conglomerate and Hollybush Sandstone were submarine volcanic grits discharged from a fissure along which later the igneous mass of the Malverns burst through. 2 Phillips, however, adduced strong reasons for believing that the crystalline rocks had not been intruded into the Palæozoic strata 3 ; he was, moreover, the first to recognize igneous rocks in the lowest portions of the latter. He described ‘felspathic dykes’ and ‘interposed masses’ in the Hollybush Sandstone; and ‘porphyritic and greenstone-masses, which, erupted from below, have flowed in limited streams over the surface of the Black Shales.’ He pointed out that neither dykes nor bosses of trap occur in any of the strata above the Black (and Grey) Shales; though some of them, including those near Bronsil (numbered 108, 247, 248, & 249 in the present writer's map), are situated in, or on, the upper part of the Shales. In the vertical section (p. 51) in Phillips's work, and in the horizontal section (No. 13) accompanying the memoir, they are placed between the Shales and the May Hill Sandstone, Phillips, with De la Beche, evidently believed that the igneous rocks were in part contemporaneous volcanic rocks, the outpouring of which, according to De la Beche, ceased with Llandeilo times. Phillips, however, compares the igneous rocks of Tortworth with ‘the greenstones of the lowest Caradoc Beds

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