GEOLOGICAL REPORT, Dr. E. Neaverson visited the site and made the following observations The footing consists largely of rounded boulders among which sandstone predominates, others are dark Carboniferous Limestone, one measuring 2 ft. X 11 ft. x fft., forms the thickness of the wall (2 ft.). Some hewn, but not dressed, blocks include Millstone Grit, yellowish sandstone of the Coal Measures, and a few of Triassic red sandstone. A few shaped stones of yellowish sandstone seem to have been used as door jambs. The mill-base has a curb made of rectangular blocks of the yellowish and the red sandstones, and the millstone is of coarse Millstone Grit enclosing quartz pebbles. The yellowish Coal Measures sandstone may have come from The Moor Quarry, Holywell or some locality near there. The Millstone Grit most likely came from outcrops within a mile southwest of the site, and the Carboniferous Limstone a little further in the same direction. The Triassic red sandstone is exposed at Burton Point just across the River Dee and was used in building Flint Castle, the small quantity visible in the Hen Bias footings could easily have the same source. Numerous purple and blue slates, undoubtedly from the Caernarvonshire slate-belt, were scattered over part of the site, and even incorporated in the footings at one place. This seems to be one of the earliest records of the use of Caernarvon- shire slate in northeastern Wales.'