Of late years the Cambrian Conglomerates have received a considerable amount of attention, as it has been shown that much information concerning the nature and condition of the Pre-Cambrian rocks can be obtained by the careful examination of the materials composing the conglomerates in different areas. It is evident that rocks similar to the rolled fragments in the Conglomerates must have been present in pre-Cambrian times to yield these fragments, and if in certain areas special rocks occur abundantly or otherwise, the characters of the pre-Cambrian rocks in these areas may be to a great extent determined. The Cambrian Conglomerates in Wales and Shropshire have been very carefully examined by Prof. Hughes, Dr. Callaway, and myself, and the materials collected have been submitted to Prof. Bonney and Mr. T. Davies for microscopical examination.