The large series of combinations of copper with sulphuric acid found in mineral veins, present many features which call for attentive study.

Some of the series, as Chalcanthite and Pisanite, are easily soluble in water, while others, as Brochantite and the members of the group allied to it, are insoluble therein, and the solubility seems to run in parallel lines with the percentage of copper.

The “Basic ” sulphates have of late received considerable notice, and English mineralogists must remember with pleasure that the masterly essay by Prof. Maskelyne “On the minerals of the Brochantite group,” gave us for the first time a clear insight into the characters of some of its constituents. This elaborate, paper shewed that the ortho-rhombic varieties were clearly entitled to be divided into distinct mineral species.