THE object of the present paper is to give some geological description of the western range of the Andes, and the Tertiary formations which are developed along the Pacific coast. References are also made to the plutonic and other types of igneous rocks which are known to occur and have not been described hitherto. During the past four years the author has made a complete traverse of the Andes in Ecuador, viz, from Babahoya to Guaranda, thence to Riobamba and Baños, including the entrance to the Oriente.

IN a previous paper in the Geological Magazine (1) the hypothesis was suggested that mountains might result from the dragging together of sediments and other rocks by a convection current inthe material below the crust. It may be useful to review the present position as to how far this idea has offered an adequate explanation of mountain and other earth structures.

WHILST studying the Bibette Head Granite, the writer had occasion to devote a certain amount of attention to the rocks with which it is in contact. In the region under consideration, these are essentially of dioritic type. The Orbicular Diorite was first found in a small embayment forming part of the west side of Corblet's Bay. It was found later in a less well developed fashion, at Saye Bay. It is quite possible that extended search would prove the presence of more. For the most part the orbicules are widely scattered, but a boulder was found at the Corblet's Bay locality which shows several associated with inclusions of a more basic rock. This boulder is now in the Sedgwick Museum, Cambridge.

FOUR years ago Klemm (1926, pp. 111–15) showed that the 1 so-calledbeerbachites and gabbro-porphyrites of the Odenwald are not, as was previously supposed, dykes cutting the Frankenstein gabbro, but hornfelsed (granulitized) inclusions in the gabbro. Within the last few months has appeared the Geological Survey Memoir on the last ofthe great Tertiary igneous complexes that awaited detailed study in Western Scotland (Richey and Thomas, 193Oa). In this publication the authors have given much new information on the nature and mode of occurrence of pyroxenegranulite hornfelses associated with gabbros. Similar rocks are well known from the earlier work of Harker, Thomas, Bailey and others, on the Tertiary gabbros of Skye and Mull (Harker, 1904; Thomas and Bailey, 1924).