1. The North Creake boring shows the Chalk up to the Coranguinum zone to be appreciably thicker than at the nearest outcrops. The Chalk rests upon fine-grained Upper Greensand (possibly Albian) which is developed in addition to the normal Red Chalk.

2. The “Lower Greensand” is developed much as at outcrop, but the Sandringham Sands are thickened by one-third. There is a strong indication of a stratigraphical break in the middle of the Carstone, which may mark the boundary between the Aptian and Albian stages.

3. The Kimeridge, Corallian (Ampthill), and Oxford Clays are developed as in the King's Lynn district, and (in contrast to Southerey) normal Kellaways Beds rest on Cornbrash.

4. The upper part of the Great Oolite Series is in Blisworth Clay facies. The “Limestone” is raggy and non-oolitic.

5. The Great Oolite rests directly on bituminous shales which are believed to be of early Upper Lias date. The Middle and Lower Lias are well developed, but the latter is attenuated as a whole. There is a possible representative of the Lower Rhaetic.

6. The Trias is represented by varicoloured marls (Keuper) upon pale grey sandstone (probably Bunter). The latter rests directly on pre-Cambrian rocks comparable with tuffs and agglomerates of Chamwood.

In a recent paper (Nockolds, 1946) it was shown that certain granite-aplites associated with acid plutonic rocks of Caledonian age in Western Scotland fell on, or were very close to, the plagioclase-potash felspar-quartz cotectic curve (the granitic cotectic curve), the approximate position of which could be determined from experimental data now available. It seemed of interest to determine whether other granite-aplites from other areas behaved in the same way and chemical analyses of granite-aplites and related rocks were collected from the literature with this end in view.

The object of the present short paper is to draw attention to what A seems to the writer to be a rather important omission in most recent discussions of the origin and nature of granite. In these discussions the word granite or almost equally often the word granodiorite are used as if it was to be assumed that all granites are alike and all granodiorites alike. In what follows, for the sake of brevity, all will be called granites, as a general class-name, without discriminating each time on small points of petrographical difference. Now all granites are not alike, by any means. They show wide variations, not so much in their main components of quartz, felspar, and ferro-magnesian minerals (the essential minerals, according to definition), but in their minor constituents and accessory minerals and still more in some of their accompanying phenomena. By this last expression is intended not so much their metamorphic effects, in the narrow sense of the word, but what is commonly called pneumatolysis, and still more importantly, the accompanying ore-deposits, if indeed it is possible to discriminate between these two categories.

In connection with a recent investigation of the geochemical changes leading up to granitization, the writer (Reynolds, 1946) had occasion to plot the chemical analyses of the rocks of the Kenidjack and Botallack region, Cornwall (Tilley and Flett, 1930; Tilley, 1935) on a von Wolff diagram. Since the diagram required somewhat lengthy discussion, however, it was not included in the geochemical paper. The diagram is nevertheless of interest because it presents in a new form the problem of the genetic associations of these curious rocks, characterized as they are by anthophyllite, cummingtonite, cordierite, and grunerite, and provides useful hints which might form a basis for further field investigations in Cornwall. The present paper, offering tentative interpretations of some of the Cornish rocks, is written in the hope of focusing attention on the petrogenetic significance of this region, and thus of stimulating detailed investigations, with strict correlation between field observations and chemical analyses, by which means alone the problems presented can be solved.

The war has cut us off unfortunately from much that has been proceeding in other lands, even in the way of scientific research which was of ho military significance. The records of such research are scattered through many periodicals which are not always accessible as yet in this country.