This interesting series of ancient volcanic rocks is described by the late Mr. Clifton Ward in a paper on the Microscopic Structure of Ancient and Modern Volcanic Rocks, read before the Geological Society, in a Memoir of the Geological Survey on the Lake District, and, in greater detail, in a communication to the Royal Microscopical Society. All these are illustrated by figures (in no case very good) and some chemical analyses are given in the last-named paper. I went to the hill in the autumn of 1874 and collected a few specimens, but my visit was cut short by heavy rain. A few weeks since Mr. J. Postlethwaite of Keswick, to whose kindness I have been more than once indebted for additions to my collection, forwarded to me three specimens from Eycott Hill, thinking that I might not have any rocks therefrom, and called my attention to the peculiar reddish tint of the felspar in one of them, which, as he remarked, “resembled the colour of a garnet.” These were varieties of the well-known porphyritic lava of Eycott Hill, which is described by Mr. Ward as the second lava bed in ascending order, and as being above 100 feet thick. This specimen was obtained from a boulder on the hill. On examining it and comparing it with my own (at which I had not looked for some years), I was struck with the appearance of the ground-mass, which seemed to me unusually compact and more like that of an augite-andesite, than of a dolerite or diabase, as the rock is named by Mr. Ward. I had a slide prepared by Mr. Cuttell from Mr. Postlethwaite's specimen, in which I first discovered the mineral which is described in this note, and have since had some more cut from my own specimens from Eycott and others subsequently sent by him, and (for comparison) from the lavas of Falcon Crag near Derwentwater.