In any purely stratigraphical treatment of a tectonic problem one of the greatest of the initial difficulties is always that of deciding where to begin, and in the present case this difficulty is unusually acute, since the primary object of the investigation is an endeavour to trace back phenomena occurring in later ages to causes of long antecedent origin. In more precise language, the object aimed at is to show that certain structural features of the Mesozoic rocks of the southern Midlands of England can be attributed to the recurrence of activity along old-established fold-lines of very early date.

Within the last 50 years the lower reaches of the Teifi from St. Dogmells to Cardigan Bar have undergone a complete change: the bed of the river formerly lay near the west side of the estuary as far as the Webley Arms, and this point in the river was then known as Pwll Cam (“the crooked pool”), as it was here that the river took a sharp bend describing an ogee curve by way of the spit to the east of the present sandbanks: this old river channel lay in clay, unlike the present shallow river bed on the east side of the estuary, and quite big vessels could float even at low tide in front of the Webley Arms, which is now a low stretch of mud banks covered at high tide. A wreck, which laid up over two or three tides, was the simple means of effecting this change in the river's course. Since then it has led to other comparatively rapid geological changes: the Manian-fâch stream, which has its source in the Pant-y-Groes plateau, used to flow almost direct into the Teifi, when in its old course; now, however, since the bed of the Teifi, on leaving the Battery Point, crosses over to the east side of the estuary, the whole of the estuary to the west has been silted up with sand and mud, and this has been accelerated by the formation of sand-banks right across the mouth of the bay: consequently the Manian-fâch stream, on emerging off the mainland, is now deflected to the S.E. and flows for about a mile approximately parallel to the main river, though in the opposite direction, before joining it nearby the Battery Point. The watershed of the roughly triangular strip of sand flats, seen at low tide, lies very close to the present river bed, so that practically all the water off this area at low tide drains first into the Manian-fâch, and thus describes nearly a complete circle twice daily. This instance is analogous to, but not quite homologous with, that of the Eiver Aide in Suffolk, the original mouth of which has been deflected more than 12 miles south by currents from the north.

During the course of work on the Pliocene deposits of West Cornwall, the writer had occasion to search a wide area forspecimens of that increasingly rare but fascinating rock, the Wolf Rock phonolite. Inquiries were mainly confined to the most likely places for securing such material, apart from the rock itself, i.e. at the cottages of fishermen accustomed to work among the dangerous reefs off Lands End and the Scilly Isles. Although personal efforts to find such specimens provedby no means abortive, it was ultimately through the good offices of the Honorary Secretary and Curator of the Royal Geological Society of Cornwall, Mr. J. B. Cornish, that excellent specimens of the Wolf Rock phonolite, Longships schist, and Seven Stones porphyry were obtained from a local inhabitant, who apparently had an eye for novelties to adorn his domestic mantelpiece.

The question of the supposed isostatic adjustment of the earth's crust to increase or decrease of load has recently come prominently to the fore in connexion with the Wegener hypothesis and Joly's theory of geological transgression and revolution. The principle itself is fairly well established by several independent lines of evidence, but there is room for clearer thinking as to the mechanism attending its operation. Very varied opinions are for instance held as to therapidity and completeness of the adjustment, and unjustifiable assumptions are made with regard to the displacement of magma beneath depressed areas. It is very necessary to keep an open mind on these questions and to search the available evidence for means of defining the nature of the attendant sub-crustal movements.