The above table is a list of all publications which contain original crystallographic work, observations, or figures relating to Bournonite ; it omits the names of many other works which mention the mineral, but merely contain information compiled from earlier sources; and it refers only to such works as are concerned with the crystalline form. The complete history of the crystallography of Bournonite will therefore be found in the above publications. The most important and comprehensive of these is the monograph of Zirkel published in 1862 ; this paper contains a summary of the previous literature and the results of many new observations, together with a large number of new figures.

In working on the isomorphism of Tourmaline I have been struck by the very peculiar development of a fine crystal from Pierrepont, New York, now in the Cambridge Collection.

The crystal is doubly terminated, of a jet-black colour and splendid lustre. It weighs 814.88 grammes, and measures 1⅙ inch by 1 inch by ½ inch.

The Periodic Law of the Chemical Elements first foreshadowed by Newlands, and subsequently developed by Mendeleeff and Lothar Meyer, states:—(1) The Properties of the Elements are a Periodic Function of their Atomic Weights. (2) The Properties of the Compounds of the Elements are a Periodic Functiou of the Atomic Weights of their Constituent Elements. This law was explained and illustrated by several examples in the case of both chemical and physical properties, and attention specially directed to the division of the elements, as arranged in Mendeleeff's table (Ann. Chem. Pharm. ; Suppl. 1870-72, p. 151) into odd and even series, and to the somewhat peculiar character of the eighth group of that table. These points were further illustrated by a reference to Lothar Meyer's curve of the elements (Mod. Theor. der Chem.).

Deposits of Diatoms have been long known to exist in Scotland, but such deposits have so far always been of limited extent. Specimens for the microscope have been readily obtained from certain localities, such as Peterhead, but the occurrence of large deposits covering great tracts of land was unknown.

In the year 1881 my attention was directed, by Mr. Hamilton Bell, to a white substance he had obtained from the Peat of Aberdeenshire. During April, 1882, I read a short paper before the Edinburgh Geological Society in which I gave the analysis of a sample received from Mr. Bell, with particulars furnished by the Rev. Geo. Davidson, Minister of Logie Coldstone, Dinner, who also kindly furnished a list of the Diatomaceæ he had identified in the deposit. The list contains some 200 species.

The Harz Mountains rise from the great plain of secondary and tertiary formations in the western part of Prussia, about 130 miles inland from the seaboard at the mouth of the Elbe. Like the Thüringer Wald and other adjoining ranges, the Harz trends in an approximately east-south-east and west-north-west direction, and resembles on the map an elongated ellipse with a northern flattened side some 50 miles in length. It has been compared to a single mountain with large shoulders, culminating in the celebrated Brocken, 8,746 ft. in height. A line drawn through the Brocken from north to south roughly divides the region into two parts.

Perhaps the most difficult question in the science of Geology at present, is the explanation of the origin of the metamorphic crystalline rocks which occupy large areas on the surface of the globe. These rocks have been generally regarded as having undergone a vast amount of change in lithological character, to which the term metamorphism has been applied. By local or contact metamorphism is meant the transformation which has been effected in ordinary sedimentary strata by the intrusion of igneous rocks, the extent of which depends on the relative size of the intrusive mass.

This body is a hydrocarbon which has been classed under the Asphalt group ; but, unlike Asphalt, it does not melt at 100°C., nor is it at all soluble to the extent Asphalt is in such solvents as ether, oil of turpentine, benzol or carbon disulphide. When heated in a closed tube it shows incipient melting after intumescing, but, at the same time, it decomposes into its constituent gases. This chemical change takes place at 300°C. In the above solvents about 5 per cent. of bitumen is obtained. Carbon disulphide softens the mass throughout to a pasty consistence.

With little else than the trouble of surveying one of the finest of Edinburgh landscapes, the tourist beginning work amongst the débris just to the south of where Samson's ribs overhang the road, and continuing on the road along Salisbury Crags to Holyrood Palace, will meet with a continuous display of the relations specially of zeolitic minerals, and their containing rocks. If he care to pursue the literature of the subject, Daubrée's investigations on the genesis of zeolites, as well as Allport's, Bonney's, and Geikie's petrological researches into the microscopy of the rocks in question, will suggest oven more lengthened studies.

The parish of Engie in Banffshire lies on the south shore of the Moray Firth, to the East of the Spey. From the Spey to Buckle on the East the rock is Old lied Sandstone, which extends from the sea inland for about two or two and a half miles. This sandstone area is bounded on the south by a series of clay-slates and mica-schists. Both on the low and high grounds of this little parish, specimens of Kyanite were often picked up, sometimes associated with quartz, and sometimes with the schistose rocks of the district.

In " Notes on some Minerals of the Mawddach Valley, Merionethshire," Min. Mag, Vol. III. p. 122, I referred to their general auriferous character; and to the occasional occurrence of flee or native Gold in workable quantity, often in states of Electrum, &c.

Since then I have been experimenting rather large!y with the auriferous lode-stuff and its enclosing Silurian slate-rock, just at its junction with the coarse Cambrian (or, it may be, pre-Cambrian) sandstone, about 1,000 feet up the Gwynfynydd or white mountain, ascending from the beautiful waterfalls known to tourists as Pistyll-y-Cain and Rhiadr Mawddach.

In the Article "Mineralogy,"in the Encyclopædia Britannica, written by Professor Heddle, of St. Andrew's, that gentleman gives the formula of Zoisite :—

4 CaO, 3 Al2O3, 6 SiO2+H2O.

Alumina 29·8; Lime 24·35; Oxide of Iron 2·8; Silica 40·3; and Water 2·1.) Cleavage, brachy-diagonal, perfect : H=6, G—3·2 to 3·4. White, brownish gray, and dark green. Localities, Glen Urquhart , Dalnein (Grantown), and Alt Gonalan, Inverness-shire ; Sterzing in Tyrol, the San-Alp in Carinthia, the Urals, and Connecticut.