Previous opinion sums up in favour of the continuity of the three boundaries, the entire line being one of dislocation in the east, dislocation and intrusion in the west. Previous opinion also favours the view that, inside the boundary-zone, not only are the Start-Lizard schists continuous, but they have features comparable with some of the Alpine “Schistes lustrés”, with recumbent folding at the Lizard.

The boundary-zone is defined as a belt of variolite (ophiolite), exotic blocks, and serpentine intrusive in, and contemporaneous with, a great thrust.

Recent work by the writer has shown that some of the beds outside the boundary-zone are a “facies flysch”. Younger beds come in towards the west, in association with the westerly pitch visible in the older beds in South Devonshire; geanticlines occur in the Lower and Middle Devonian respectively, of South Devon and South Cornwall. In an area further north some of the beds show an accumulation of folds comparable with those of the “autochthonous sedimentary” in front of some of the great Alpine nappes; recumbent folding is prevalent in both Devon and Cornwall. The Cornish Flysch was deposited under conditions such as might have preceded a great nappe movement; it is described in relation to the exotic blocks and serpentine in the fracture.

The much younger Alpine Flysch also includes ophiolites and exotic blocks, with serpentine intrusive in the fractures upon which the great nappes advanced. According to some authors, the nappes arose from recumbent folds based on geanticlines.

The similar direction of both the Cornish (Variscan) and the Alpine movements makes possible a comparison in certain effects as, for instance, the southward increase in albitization and metamorphism, between the great Alps and the similar but older, comparatively tiny, flattened, and denuded relic in south-west England.

These cases are also strikingly paralleled by a zone of basic igneous rocks and exotic blocks which overlies the Himalayas.

The evidence appears sufficient basis for the suggestion that the Start-Dodman-Lizard boundary-zone may be the relic of a great Variscan nappe, associated with the fan-structure of Cornwall.

It is difficult to draw the line between aridity and semi-aridity, just as it-is difficult to differentiate between humid and semi-arid climates as they affect the development of landscape forms. No hard and fast divisions based on rainfall figures can be adopted. Evaporation, in part controlled by temperature, and the seasonal distribution of rainfall are also important factors. “The rainfall regime is divisible”, according to. Bryan, “into the episodic and the periodic. In the episodic type rain falls in storms that are highly variable in intensity and are scattered through the year; in the periodic type precipitation is concentrated in one season, either summer or winter. In areas having the periodic type vegetation is adjusted to the wet season, and a relatively greater vegetative cover is possible with low rainfall. The Mediterranean region and California have the periodic type of rainfall, with winter maximum and mild temperatures. Thus in many sub-areas the land forms under mean annual rainfalls of 15 to 20 inches are very similar to those of humid regions, although the soils … are quite like those of other arid regions. The episodic rainfall, because of its variability in time throughout the year, is less effective in promoting growth, and the vegetative cover may be so scant with rainfalls of 5 to 7 inches that geomorphologically the region is essentially a desert. Episodic rainfall as high as 15 to 20 inches may produce steppe conditions. … In general the warmer areas have a relatively scantier vegetation with the same rainfall regime. Including this relation all varieties of hot and cold deserts or semi-arid climates are possible (2).”

The origin of the West Cumberland haematites is one of those unsettled problems that have exercised the minds of geologists and miners for more than half a century. Theories have been evolved, but not one can claim general acceptance. It is not my purpose to discuss these theories here, but the consideration of one of them was directly responsible for the examination of the reddened Carboniferous rocks that form the subject of this paper. This theory, first advocated by J. G. Goodchild and later supported by Dr. B. Smith, may be stated briefly thus: The New Red Sandstone rocks were the immediate source of the haematites. From these rocks the iron was carried in solution to lower levels by the downward percolation of meteoric waters. The theory had the merit of explaining, not only the haematite deposits of the Carboniferous Limestone of West Cumberland, many of which occur beneath the New Red Sandstone Series, but also the reddened Carboniferous strata frequently found in North-Western England, beneath and fringing the base of the Permo-Triassic rocks.

The purpose of this paper is to discuss methods by which the data of sedimentary petrology (mineralogical composition, grainsizes, etc.) may be most usefully recorded upon a map. The ultimate aim which the writer had in mind when commencing this work was to learn something of the palaeogeography of North-East Yorkshire during Middle Jurassic times.1 It soon became evident, however, that a map upon which the data have been registered may be a record not only of the conditions at the time of deposition but also of the subsequent mineralogical changes in the rocks themselves and, what was less expected, of the tectonic development of the region as a whole.

In the search for oil on asymmetrical anticlinal structures it is of prime importance to know the position of the axial “plane” of the fold, for it is never safe, even where asymmetry is only moderate, to drill a test well across the axial “plane” and so penetrate the steep flank. Where such a thing has happened, the evidence in regard to the oil prospects of the area can generally be ruled out as inconclusive, and in that way much money and effort have been wasted.