I wrote the first of these papers more with a view of obtaining some help in my own work than with any purpose of carrying forward the discussion of the subject myself. But no help having been given me, I must proceed cautiously alone, and arrange the order of my questions; since, when I have done my best as carefully as I can, the papers will be nothing but a series of suggestions for others to pursue at their pleasure.

The graceful outlines, smooth curves, and flowing contours of the Chalk hills are well known to southern geologists; indeed these hills are the most marked feature of the south-east of England. Those who hold that their form has been given by the sea, point to the winding ridge, and say how like it is to many a coast with its succession of capes and coves; even so distinguished a writer as Sir C. Lyell remarking that “the geologist cannot fail to recognise in this view (of part of the South Downs) the exact likeness of a sea-cliff”. And truly it is so; but let us examine this likeness more closely, and it will be seen that the argument founded on it, plausible enough on the surface, is superficial only, and fails utterly when rigorously tested.

The strata lying above and below the Lingula Flags have already been well described and illustrated: the Menevian Gronp below, by Messrs. Salter and Hicks, and the Tremadoc Group above, by Messrs. Homfray, Ash, and Salter. The great mass of strata lying between has not fared so well, through several notice of it, to which I shall refer, have appeared. In the present paper I propose to describe these strata in detail; and the remarks I have to offer embody the results of three years' researches, during part of which I have had the advantage of the company and able co-operation of Messrs. Ezekiel Williamson and J.C. Barlow, whose discoveries I shall have to mention in my description of the rocks and their fossil contents. To facilitate the study of the district around Dolgelly, which is exceedingly faulted and complicated, I have carefully mapped out nearly the whole of the rock exposures. This may seem to have been unnecessary, seeing that we have already the Geological Survey maps of the district. But since the officers of the Survey examined and mapped out the rocks of Merionethshire, from fifteen to eighteen years have elapsed, and the maps which then added so much to our knowledge are now far behind our requirements.

Since the researches of Heer into the Miocene Flora of Switzerland have invested the theory of a Tertiary Atlantis with some degree of probability, other observers have come forward with arguments on the one hand which lend support to that hypothesis; whilst on the other hand it has been attempted to prove that the facts (as to the presumed migrations of plants and animals) are to be accounted for rather by a connection between Europe and America through the Asiatic region. My examination of the Jamaican fossils first led me to support a modification of the original view taken by Heer, and in April, 1866, I communicated to the Geological Society a paper bearing on the subject. That paper was read on the 20th of June, 1866, and an abstract of it appeared in the August number of this Magazine. I propose, on the Present occasion, to make a few remarks on the probility of the former connection between the eastern and western shores of the Atlantic.

Since Sir Charles Lyell published his most accurate and detailed paper “On the Tertiaries of Belgium and French Flanders,” geologists could only differ in their opinions on the facts mentioned by him, New discoveries have been made in Belgium only in the last few years; besides the splendid cuttings in the ditches for the fortification of Antwerp, about which I am going to speak afterwards, there has been found, near Mons, by sinking a well, a thick bed of lime and limestone at the base of all hitherto-known Belgian Teritiary beds, containing numerous and well-preserved Tertiary marine and fresh-water mollusca. The discoverers, MM. Cornet and Briart, Engineers of Mines, and most zealous geologists, described very carefully the geological position and afterwards the extension of these lowest Tertiary beds in Hainaut. In their first paper they had tried to determine the Molluscan fauna of this basement bed, after Deshayes' works; but, out of 150 species, they could name only 22, and amongst these there are still some very doubtful ones.