This paper deals with various specimens received at the Imperial Institute from Ceylon. Some of these specimens were obtained by Dr. A. K. Coomaraswamy at Wa]aweduwa, in the Bambarabotuwa district of the Sabaragamuwa province, during the course of the Ceylon Mineral Survey. Walaweduwa is a little to the north of the Bambarabotuwa locality where thorianite has been found in conslderable abundance. Dr. Coomaraswamy also found specimens in the upper part of the Alupola oya, a stream in the same district. A chemical examination of these specimens showed that titanium dioxide, zireonia, thoria, lime, and iron oxide were the chief constituents.

Early in the year 1912 extensive modifications were introduced in the apparatus for slitting rocks, and for grinding and polishing thin-sections in the Mineral Department of the British Museum, the whole of the alterations and additions being carried out to my designs by Messrs. Plume and Parry, 47 Old Compton Street, London, W. The changes made were chiefly in the means for holding the specimen or section during the operations; much of the actual machinery remained unaltered, and some of it dates back to the initial installation, upwards of forty years ago. It may not, therefore, be without interest if a brief description of the history of the installation be included with the description of the present apparatus.

Nine years ago (in 1904) I described a diagram—the moriogram, as I called it—which served for the graphical determin.stion of angles and indices in the case of zones in which the principal poles included a right angle. It was, therefore, restricted in its application to zones in the cubic, tetragonal, orthorhombic, hexagonal, and rhombohedral systems, and to zones in the monoclinic system passing through the pole of symmetry. Although the moriogram may be used with sufficient accuracy for practical purposes in the case of many substances with triclinic symmetry, in which the angles between the principal poles differ little from right angles, there necessarily remain many instances in which it cannot be applied with any approximation to accuracy.

Thomas Pennant was born at Downing, Whitford, near Holywell, in 1726. A contemporary and correspondent of Linnaeus and Buffon, he is well known to zoologists as a pioneer of British zoology, and to him were addressed the letters of Gilbert White which form the greater part of 'The Natural History and Antiquities of Selborne'. He travelled very extensively in the British Isles and wrote many accounts of his tours, perhaps the best known being his account of London and his 'Tour in Wales'.

As is well known, the dolomite of the Lengenbach quarry is rich in pyrites and has some rutile.; the crystals of the latter being very small and somewhat infrequent. It seems therefore strange that the presence of hematite or ilmenite has not hitherto been recorded. This last summer I obtained a specimen which showed a minute black crystal with numerous faces, which I began examining under the impression that it was a sulpharsenite.

A crystalline deposit of sufficient interest to warrant description was brought to the authore notice by Mr. Henry Preston, F.G.S., who has recently described its mode of occurrence. The material consists of a white, glistening, crystalline powder, or a sand-like aggregate of minute crystals. It was deposited in a water-tank into which water was led through an old leaden pipe, over a mile in length, from a spring rising from the basal ferruginous beds of the Marlstone (Middle Lias) ill Belton Park, north of Grantham, Lincolnshire. The sand was deposited in the tank as a conical heap, spreading over a base of perhaps four square yards and reaching a height of seven or eight inches at its summit.

Mallard's original method was based on the measurement of the linear distance, as determined by an eyepiece-micrometer, between the optic axes in a section of the crystal at right angles to the acute biseetrix viewed in convergent light.

Professor F. Becke implored on this method by utilizing sections which were not at right angles to the acute hissetrix, but in which both optic axes were visible in the field. He projected both axes by means of an Abbe camera lucida on to a revolving drawing-table, and by means of the Mallard equation plotted the axes on a stereographic projection and thus obtained the optic axial angle, the angles of course being corrected for refraction to the true angles in the crystal section. Professor Becke subsequently, by utilizing the Biot-Fresnel law, formulated a graphic method of obtaining the optic axial angle from a section in which only one axis was visible.