The Old Red Sandstone Volcanic Suite of eastern Forfarshire

I ntroduction . T he lavas described in this paper are those which occur in the Old Red Sandstone series in that district of Forfarshire which is bounded on the east by the coast between Arbroath and Montrose, and on the west by a north-south line through the town of Forfar. It is roughly a rectangular area of country, undulating for the most part, but with occasional more prominent hills; of these, Dunnichen Hill (761 feet) and Turin Hill (825 feet) are among the highest. The whole district is well covered with drift deposits, and natural exposures are rather few. However, this is usually less true of the lavas than of the contemporaneous sediments, since the former offer greater resistance to weathering, and form most of the more prominent topographical features; quarries, too, often provide easy means for collecting fresh hand specimens of lava. North of Montrose, the topography continues unchanged into Kincardineshire, as far as the Highland Boundary Fault; south-west of Forfar, the ground begins to rise towards the eastern edge of the Sidlaw Hills, while to the north-west it merges into the Plain of Strathmore. South of the latitude of Arbroath the country slopes up towards the ridge of hills which overlook the River Tay. There is as yet much to be studied concerning the petrographic aspects of the Old Red Sandstone lavas of the Midland Valley as a whole. Geikie ( 10 ) was the first to give a generalised description of them, and in more recent times, various authors have described