The place-names of mineral-localities in central Europe have presented many difficulties in connexion with the topographical indexes to 'Mineralogical Abstracts', and also in the much more extensive cardindex of localities represented by specimens in the Mineral Collection of the British Museum which has been in progress for many years. Further, I have been asked from several quarters to prepare a short check-list of equivalent names of those localities most frequently mentioned in mineralogical literature. When, in August 1927, Prof. F. Slavík was good enough to send me a copy of the manuscript list of Czechoslovakian localities and minerals which he had prepared in French for Prof. A. Lacroix for use in the Paris Museum, I at once recognized that with his co-operation a much more useful list could he prepared. This he readily assented to, and he has since extended his original list to include other countries.

The isomorphous replacement of one element by another, in a pair of crystalline salts, is usually accompanied by a substantial change in the molecular volume. This progression is exceptionally well illustrated in the 'eutropic' elements K, Rb, Cs, and Cl, Br, I, which formed the subject of the first part of this paper. It was there shown that the differences produced by interchanging these elements stood in the same ratio in all the salt-series, though the size of the differences varied with the acid radicle. The object of the present note is to draw attention to the existence of similarly constant (though different) ratios for the salts of O, S, Se, Te, and for the salts of Ca, Sr, Ba. The spacings in these compounds have recently been obtained by X-ray determinations, in many cases due to u M. Goldschlnidt and his co-workers, so that it is possible to verify the rule of proportional differences in these series, although the results do not possess an accuracy so high as that of densities measured by the pyknometer.

The object of this note is not to give elaborate descriptions of rocksections, but to call attention to tile fact that the old volcano of Nimrud, situated on the west side of lake Van in Armenia, was the centre of eruption of alkali-lavas presenting striking similarities to some of the alkali-rocks of the tlift Valley in East Africa.

To Dr. Felix Oswald, in his book on the geology of Armenia, we owe a detailed description of this ancient volcano, of which the vast crater, now half occupied by a deep lake, is more than five miles across. An interesting series of the lavas from the volcano was collected by Dr. Oswald and was presented by him to the British Museum. On looking over thin slices of these rocks under the microscope, I was at once struck by the surprising resemblance of some of them, with their phenocrysts of anorthoclase and scattered tufts of aegirine and the soda-amphiboles, riebeckite and cossyrite, to rocks in Prof. J. W. Gregory's collection from the Rift Valley which I had described.

The following notes are intended to bring to the notice of workers on heavy mineral grains the possible confusion between blue tourmaline, purple tourmaline, glaucophane, lepidolite, andalusite, pleochroic sillimanite, and dumortierite. Dumortierite (when blue) is very liable to be passed over as the more common mineral glaucophane, the optical properties of the cleavage-flakes of these minerals being similar in several respects.

Having seen a grain of dumortierite from the Wealden of Surrey, kindly lent me by Mr. H. A. Hayward, I was impressed by the remarkable nature of its pleochroism. A day or so later, while examining some concentrates of the Blackheath Beds of Shirley, Surrey, belonging to Mr. G. M. Davies, I came across a single grain which he had described as glaucophane. The pleochroism seemed too intense for a grain of glaucophane of that thickness, and it occurred to me that the tint observed, when the grain was in the position of maximum absorption, was exactly that of the dumortierite grain.