8 GEOLOGICAL MEMOIRS. 



sulphur witli whicli it is invariably associated. The sulphur occurs 

 either in pure yellow nodules containing more than 95 per cent., or 

 in masses of a brownish or greenish grey containing from 50 to 60 

 per cent, of sulphur, with numerous Paludinse, Limnsei and Planorbes 

 converted into sulphur, as well as coniferous and aquatic plants, the 

 form of which is perfectly preserved. 



Seven beds of this combustible have been hitherto discovered re- 

 gularly alternating with the bituminous gypseous marls. The most 

 abundant is found in the mine called Santa Ana de Herrero, which 

 has a thickness of 6 palms ; they increase in produce to the north as 

 far as a spot called Zarcillos y Humbria de Cascante. They all in- 

 cline 6° to the east. 



IV. The fourth group, the lowest of the tertiary formation of 

 Teruel, consists of sandstones and coarse limestones (calcaire grossier) 

 without fossils, blue marls vdth beds of lignite a foot thick, but of 

 inferior quality, and lastly of sandstones graduating into conglome- 

 rates resting on the cretaceous formation. 



Finally, it is stated that considerable beds of lignite, used for va- 

 rious purposes, are found in the province of Teruel, in the neighbour- 

 hood of Utrillas, Montalban, Peiia-roya, Alloza, Rubielos de Mora, 

 &c., the strata of which belong to the lower portion of the tertiary 

 formation. These lignites may be considered as the continuation of 

 those of Mequinenza and La Granja de Escarp in the provinces of 

 Lerida and Zaragoza, which, according to the geological conditions of 

 the country, are a counterpart of the province of Castellon de la Plana. 



The same volume (p. 300) contains a memoir by Don Joaquin 

 Ezquerra del Bajo on the tertiary formations of Central Spain. After 

 lamenting in pathetic terms the want of zeal for the study of natural 

 history amongst his countrymxcn, and giving a general outhne of the 

 great geological phaenomena, the author proceeds to describe the ter- 

 tiary basins of the Douro, the Tagus, the Ebro, and the Guadiana. 



Basin of the Douro. 



The tertiary formation of the basin of the Douro extends from south 

 to north, from Mingorria in the province of Avila, to beyond Saldana 

 in the province of Palencia, a distance of 40 leagues. On the west 

 it extends to Salamanca, Zamora, and Benavente, and on the east to 

 near Reynosa. The Douro flowing from east to west, this district is 

 bounded on the north by the Asturian Pyrenees, and on the south by 

 the northern slope of the mountain-chain of Guadarrama. Its whole 

 extent may be calculated at 1600 square leagues, perhaps the most 

 extensive tertiary lake or lacustrine formation which has existed. 



The different beds of this formation, with their various relations, 

 are best seen in the centre of the basin, at a distance of 8 or 1 leagues 

 on each side of the Douro ; here the formation is laid bare to the 

 thickness of 500 feet in the ravines and water-com'ses opened out by 

 the rivers. The beds are all horizontal, from whence it may be in- 

 ferred that no eruptive agencies have been at work in this district since 

 its deposition. 



The different strata which have hitherto been examined have been 



