I Have already answered this question in the affirmative in my papers on “Metamorphism in the Malvern Hills,” though I am aware that the assertion has been contested. Nevertheless, the possibility that diorite and quartzite may have a common origin was suggested by Prof. Zirkel as far back as 1876; and in 1892 Mr. W. S. Bayley, of the Geological Survey of Minnesota, distinctly affirmed that a certain quartzite was nothing more or less than “a completely altered gabbro.” My conclusion, therefore, is not without support, and, though it has been strongly attacked, it refuses to succumb. I trust I shall be allowed in the present paper to reply to one or two of the objections to it. My remarks refer only to the Malvern area.