As Dr. Callaway has asked in a recent Number of the Geological Magazine for the grounds on which I suggest that some of the volcanic rocks of Shropshire may perhaps be classed as Cambrian, I take this opportunity for bringing before your readers the present state of the inquiry into the nature and classification of the earliest sedimentary rocks in this country. This inquiry has been spoken of by Dr. Callaway as the “Archæan controversy”; but we must not necessarily call everything that is earlier than the Cambrian “Archasan,” any more than in old days it was right to call everything Precarboniferous “unfossiliferous greywacké”; nor should the inquiry be considered a controversy in its present stage, but rather a search for more accurate knowledge.