The following letter has been forwarded to me with a request ot make a few remarks upon the flint-cores mentioned by General Twemlow:—

The district of Cleveland, long known for the beauty and variety of its scenery, has during the past few years acquired great importance through the discovery of valuable beds of iron ore in the Middle Lias. So much has been written on this district, and in a lesser degree on East Yorkshire generally, that the geological structure of this country must be tolerably well known. My object then is not so much to describe the beds as to give some notes on the physical geography of the country, explaining the relation of its present surface outlines to its internal structure, and to enquire by what means those external features have been produced.

The article by Mr. Mackintosh on “The Cliffs, Gorges, and Valleys of Wales,” in the September number of the Geological Magazine, raises so many questions in opposition to the views I endeavoured to support in the previous number, that I venture to offer a few further observations on some of the more salient points in which Mr. Mackintosh differs from the advocates of subaërial denudation.

A small quantity of a highly ferruginous water was lately given to me for analysis by my friend and former colleague, Dr. John Bayldon. He had collected the sample himself at the spring in Mimosa-Dale, Uitenhage, South Africa, where also he had obtained specimens of the iron-salts which are freely deposited by the chaly-beate waters.

The Flint and Stone implements sometimes found in this and other countries seem to form a sort of connecting link between geological and human antiquity; they are certainly the work of man, and they may possibly be older than the invention of metallurgy, and nearly coeval with the human race: it becomes therefore a matter of some interest to determine whether and to what extent the use of stone implements may have been contemporary with that of metals; and the references below given will, it is hoped, assist in elucidating this question.