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is more economical in the end to use a hard stone of the greenstone type for roads, though the first cost may be considerable, rather than a soft stone, which though cheap at first, may be perishable ; just as steel rails for railways have proved their superiority in the matter of cost, in the long run, though at first much more expensive than rails of rolled iron. The following are analyses of three specimens of diorite from the ‘ Sanctuaries,’ St. Me wan, Cornwall: 1 Silica Alumina Oxide Iron Lime Magnesia Potassa Soda Sulphur Phosphoric Acid Titanic Acid .. . Water I. 11. 47.66 ... • - 47-32 17.50 ... ... 17-15 21.94 ... ... 22.60 4.20 .. . 4.03 trace ... . .. trace 2.43 ... • • • 2.33 5.19 ... ■ 527 trace .. . . .. trace 0.16 ... 0.18 trace .. . trace 0.83 ... ... 0.18 III. 47-79 17-83 32.49 4.10 trace 2.15 5-88 trace trace trace 0.76 99-9 1 99.70 99.91 Gabbro. A name proposed by L. von Buch for a rock composed of labradorite and diallage, smaragdite, or hypersthene, and usually some other minerals. 2 It is variable in composition, and not of frequent occurrence. Diabase. (Hyperite, Scandinavian Trap.) A crys talline-granular compound of oligoclase, labradorite, 1 Phil. Mag., Feb. 1871. 2 B. von Cotta, Eng. vers, p. 150.