The gold-bearing Bittleford rock does not occur in situ at the type locality. It is a true igneous rock, and a product of a somewhat aqueous fraction of the magma represented by the older of the two main granite types. Its affinities are with the pegmatites, and its position in the Dartmoor suite is among the minor intrusions. The gold and silver which it contains appear to be no less primary than the rest of the minerals with which these metals are associated.

The laboratory work necessary in connexion with the investigation of these rocks was carried Out in the Departments of Geology and Chemistry, Imperial College. The authors express their thanks to Professor W. W. Watts and Professor H. B. Baker for laboratory facilities kindly placed at their disposal.