A tendency to assume crystalline forms is a property of all crystalloids ; its full or imperfect development depends on external circumstances.

Crystals produced in laboratories are generally inferior to natural crystals of the same substances, prohaby because of their too rapid formation. The faculty of crystallization is modified by specific dispositions inherent to the substances. There are many distinct types of crystallization, connected with each other by intermediate types, and even with a transition from amorphous to crystallizable substances.

The degree of distinctness of crystals constitutes a fundamental difference. The crystals of many substances are distinct, while below a certain limit of size ; but when this is exceeded, the surfaces are interrupted by re-entering angles, or by irregular drusy cavities or excrescences constantly re-appearing when cleft away, so as, at last, to completely destroy their individuality and regularity.

The Volcanic Rocks of Lower Silurian age in the Lake District are interesting in the highest degree on many accounts, and not least so on that of the extreme metamorphism which they have undergone, partly by the deep burial they suffered during the period between the close of the Lower Silurian and the Old Red, when they were once more largely uncovered, and partly by that neverceasing action of infiltration, decomposition, solution and replacement to which all rocks are subject during the course of geological time, but to which rocks of an originally volcanic origin seem specially subject.

If there is one feature in this metamorphism of the Cumberland rocks more prorainent than another, it is the large degree to which chlorite has been developed among them, and the universality of its occurrence.

In 1861, I described (Edinburgh New Philosophical Journal, and American Journal of Science) a borate, found with glauber salt in gypsum at this place, as a new mineral, by the name of Cryptomorphite, on account of its amorphous appearance to the naked eye being resolved into one most distinctly crystalline, under the microscope.

The first criticism on the mineral was made by Prof. Geo. J. Brush (Tenth supplement to Dana's Mineralogy), who said, in effect, that it could not be accepted and named as a new and distinct hydrated borate of soda and lime, because there were already too many names in use for minerals, not clearly made out to be distinct, having more or less closely similar composition.

This quartz, the precise locality of which is unknown, is different to any that I remember having previously seen. It is apparently from a mineral vein, and consists of an assemblage of quartz pyramids, which differ from the usual form in having each angle apparently supplemented by a small prism, giving to the centre block a curious stellate appearance, fig. 8, Pl. V.

The interspaces arc filled up with minute pyramidal crystals of quartz, as well as others of chalybite and pyrites.

The fractured under surface fig. 7 shows an infinity of concentric lines of growth, the interior being composed of transparent quartz, while the outer layers are milky and opaque.

It is a well-known fact that Pyrrhotite, or Magnetic Iron Pryrites, frequently, if not invariably, contains nickel, generally with cobalt in various proportions, amounting together from traces, up to nearly six per cent., and that most of the nickel of commerce is derived from this mineral

The following notes contain in the first place the results of the examination of a few varieties of pyrrhotite, occurring in Nova Scotia, New Brunswick, and the United States, chiefly with reference to presence or amount of nickel and cobalt, and they shew also that remarkable differences exist in the intensity of the magnetism displayed, which ranges from distinct polarity in the mass, down to very iceble attraction by a magnet in the finely powdered state of the mineral, and further, that the most feebly magnetic of the specimens examined is that containing the largest per centage of nickel. The subsequent notes relate to other species from h~ova Scotia and Newfoundland.