GEOLOGICAL MEMOIRS. 



&c.). Towards the north it occupies a large portion of the province 

 of Huesca. 



The whole of the tertiary formation which occurs in the province 

 of Barcelona corresponds with the lower formation hereafter described, 

 containing, between Miralles, Copons, Segur, and Calaf, several beds 

 of good lignite, as much as ten feet in thickness. That of the pro- 

 vinces of Lerida and Tarragona corresponds with the upper portion, 

 characterized by a great developement of gypseous rocks, the thick- 

 ness of which exceeds eighty varas. 



The general section of the tertiary formation, in ascending order, 

 and with a variable thickness, gives us an incoherent conglomerate of 

 rolled pebbles chiefly calcareous ; beds of reddish plastic clay ; marls 

 more or less siliceous, yellowish, and graduating into sandstones ; 

 sandstones of the same colour, and generally fine-grained ; gypsum, 

 chiefly laminated and but slightly compact, of a white or hght red- 

 dish colour ; grey and yellow clays ; and finally, deposits of rolled 

 pebbles of older rocks more or less cemented together. Some of these 

 beds are wanting in certain localities. 



The principal features in these deposits are the above-mentioned 

 lignites, the sulphates of soda in the neighbourhood of Cervera and 

 of Artesa de Segre, and the quicksilver of the city of Lerida. 



The gypsum which occupies the greater part of the confines of 

 Robinat, one league distant from Cervera, is strongly impregnated 

 with sulphate of soda ; and a considerable quantity of this salt is ob- 

 tained by evaporation of water saturated with it by means of arti- 

 ficial excavations in the gypsum into which the water is conveyed. 



Near the junction of the Segre with the Ebro, dark bituminous 

 and foetid limestones are first seen. These are underlaid by beds of 

 excellent free-burning lignite, varying in thickness from two inches to 

 two feet. This fuel was used at very distant periods. Of late its use 

 has considerably increased. The best lignite of the Segre and the 

 Ebro has a specific gravity of 1*26. It burns easily, leaves ten per 

 cent, of ashes, and makes a good coke. The principal difference be- 

 tween this and the various lignites of Aragon and Catalonia consists 

 in the great quantity of vegetable impressions it contains, as well as 

 fossils of the genus Planorbis, which are sometimes two inches in 

 diameter, and form white stains in the middle of the coal. The 

 limestone on which it rests also contains many fossils, but they are 

 entirely confined to the genera Plmiorbisy Limnceus, and Paludina. 

 The general thickness of the lower deposit of the tertiary formation 

 of Lerida is not less than 200 varas, and terminates under the beds 

 of lignite, with others of marl, sandstones, conglomerates, and clays, 

 resting on the rocks of the cretaceous group. 



A considerable portion of the province of Zaragoza is covered with re- 

 cent freshwater deposits ; of these however no detailed account is given. 



The province of Teruel consists for the greater part of tertiary 

 beds, forming a lacustrine formation covering 25 square leagues*. 

 The author has divided this formation into four groups for the 



* The Spanish league = 4 miles, the square league therefore contains 16 square 

 miles. 



