Thomsonite was first recognized by H. J. Brooke (1820) in a JL study of the mesotypes or 'needlestones'. The 'needlestone' of Lochwinnoch and Old Kilpatrick, Dumbartonshire, was found to be an independent species, in addition to the natrolite, mesolite, and scolecite into which k. F. Gehlen and J. N. Fachs, and J. N. Fuchs, had divided the mesotype of R. J. Haüy. The new species was named thomsonite, in honour of Dr. T. Thomson, who analysed the material a few months later.

During the last year, Dr. R. H. Rastall has been engaged on an investigation of the mineral content of certain sandstones of Middle Jurassic age in north-east Yorkshire. These sandstones proved to be unusually rich in the titanium minerals rutile and anatase. In some samples the proportion of the last-named is greater than in any other specimen previously recorded, so far as can be ascertained. Some of the heavy-mineral separations also contained a number of crystals of quite unmistakable brookite, with normal crystallographic development and normal optical properties, namely Bx perpendicular to (100) and intense dispersion ρ > v. Associated with these, however, there were often observed a number of smaller crystals of very similar appearance, whose optical orientation seemed to be entirely different. In particular, no optic picture could be obtained, and the extinction between crossed nicols in parallel light was perfectly sharp, with no suggestion of strong dispersion. Dr. Rastall therefore asked me to carry out some further investigations into the nature of these crystals, which were unlike anything he had previously seen in sedimentary rocks.

Scorodite from Kiura mine, Bungo, Japan, has been known for many years. However, owing to its diversity in crystallographical and optical properties as well as chemical composition from those of other localities there appears to be some doubts as to the identity of the mineral. It has even been suggested to be possibly a new mineral having a composition akin to that of scorodite. Some time ago a number of fine crystals were placed at our disposal by the courtesy of Dr. Kô, in addition to the recent acquisition by our Institute of a few rarely found beautiful druses of the mineral. It will therefore be worth while to describe some of its main features in detail.

Although a considerable amount of work has been published On the occurrence and crystallography of fluorite, comparatively little has been done on the variations in habit of the crystal s. V. Goldschmidt's 'Atlas der Krystallformen' (vol. 4, 1913) gives 160 drawings with references for different forms and combinations of fluorite, but very few attempts have been made to explain the different habits observed. Experiments on the artificial growth of crystals by different methods; under varying conditions of temperature and pressure, and in the presence of foreign substances in the solution do not appear to have been made.