The area under consideration lies in the adjoining margins of the Geological Survey maps, sheets 21 and 22, Scotland, on which a large number of volcanic necks are shown to occur. Sir Archibald Geikie (1897, pp. 394 seq. ; 1903, pp. 65-6), who has given several short accounts of them, considers that they are the sites of some of the volcanoes which gave rise to the Calciferous Sandstone lavas. During the recent revision of this area by the Geological Survey several new volcanic necks have been recognised, and fresh evidence has been gathered about some of the others. In the map of the district (Fig. 1) the various necks are each given a separate number, and for facility of reference the same numbers will be used in the following account. Description of the Necks. Vents Containing Acid Materials. —The Irish Law vent (No. 1) forms the south extremity of the great volcanic centre of Misty Law, and most probably represents a late phase of activity. Its margins are only seen on the west in the sections on the sides of Rye Water Head, where a coarse-grained pink and green volcanic breccia is in contact with a pink felsitic rock. Further north the margin can be seen cutting across the Gogo Water. To the south it has been traced in a south-easterly direction to the west slopes of Knockside Hills (Figs. 2 and 3). The eastern margin is covered by peat, but is taken as running in a north-easterly direction. Several masses of This 250-word extract was created in the absence of an abstract