On the Secondary District of Portugal which lies on the North of the Tagus

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Abstract
General Sketch of Portugal .—So little is known of the geology of Portugal that it may be interesting to give a general sketch of that country before proceeding to the details of the district which is to form the subject of the following paper: this has been drawn up from my own observations and from a variety of sources mentioned in their places. Commencing at the north with the Spanish province of Gallicia, which has been described and roughly mapped by Schulz*, two-thirds of the surface of Gallicia are formed of granite, gneiss, mica-schist, and other crystalline rocks, which cover nearly all the western and middle portions of the province: the eastern side is principally formed of slate, grauwacke, &c., classed by Schulz as Transition Rocks , among which we may expect future observers to find the Silurian and Devonian formations. The strike of the slates varies, but its mean appears to be about N.N.W. There are some small patches of secondary red sandstones and marls scattered over the province, of which the age has not been ascertained; here and there a small tertiary deposit occurs; and the bottoms of many of the valleys are filled up with thick deposits of gravel. Passing southward into Portugal, we find the same formations continued in nearly the same direction : the greater part of the province of Minho and the western side of Traz os Montes consist principally of crystalline rocks; but the rest of Traz os Montes is mostly formed of slates, which

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