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feldspar particles. Within the feldspar, along the cracks, microperthite has developed which does not show any dynamic action. The granite is much later than the gneiss, but like it has to some extent suffered from dynamic action. In general it is massive, or nearly so, but there are zones of shearing where granulite and gneiss have developed. Also in one portion there is a dark rock approaching a diorite, into which the granite grades, but this is regarded as a basic segregation from the original magma. The crystalline limestone is rather uniform in its character, but where intruded by the granite, it is more coarsely crystalline, and various metamorphic minerals have developed. Near the base of the limestone is a pyroxenic rock which is schistose, highly contorted, and is of somewhat doubtful origin, in the field being regarded as sedimentary, and under the microscope having an appearance which suggests an igneous origin. In this pyroxenic gneiss occasionally scapolite is found. The Potsdam is a pure vitreous quartzite, indurated by the process of cementation.

Nason,^[1] in 1893, describes the gneissic rocks bearing iron-ore in the Adirondack region as precisely like the Mt. Hope type of rock, bearing the New Jersey magnetites, and it is thought that the two are probably contemporaneous, bedded deposits. These gneissic ores are non-titaniferous, and are to be discriminated from the titaniferous iron ores which are associated with the labradorite rocks or norites of the region. These in occurrence and association are wholly distinct from the ores belonging in the gneisses.

Lawson^[2] describes the Santa Lucia granite of Carmelo Bay as resting unconformably below the sedimentary rocks (Miocene) of the Carmelo series. At the base of the latter is a fine basal conglomerate. Across the Bay of Monterey, in the Santa Cruz range, granite without doubt of the same geological range bears a similar relation to rocks which are of not later age than Cretaceous. The granite is therefore, at the latest, of pre-Cretaceous age.