450 SCIENCE PROGRESS. 



the eruptions and the formation of the valleys took place 

 in the Tertiary period. 



Eruptive Masses. — Mention has already been made of 

 the basaltic eruptions which took place at the close of the 

 Cretaceous period, and of the outbursts of ophite which are 

 probably of somewhat later date. But it is probable, too, 

 that some of the great masses of eruptive granite which 

 are so prominent on the geological map of Portugal are at 

 least as recent as these. Ribeiro had long maintained that 

 the granite of Cintra was of Tertiary age, but he never 

 published his evidence. Choffat has shown that this granite 

 has sent out veins into the base of the Malm ; and as the 

 higher beds of the Malm and the whole of the Cretaceous, 

 up to the top of the Cenomanian, follow upon these without 

 any sign of disturbance, he holds that the granite cannot 

 have been intruded until after the deposition of the whole 

 series. It cannot therefore be older than Upper Cretaceous 



One of the most interesting of the eruptive masses of 

 Portugal is that which forms the greater part of the Serra 

 de Monchique. This consists chiefly of elseolite syenite, 

 which seems to have forced its way into the Culm of this 

 region without ever reaching the surface. The gradual 

 cooling of this mass under great pressure has led to the 

 formation of some interesting varieties of dyke rocks 

 which have been described by various writers, and subse- 

 quent denudation has exposed the resulting igneous com- 

 plex (24 and 25). 



BIBLIOGRAPHY. 1 



(1) Ben-Saude, Alfredo. Notice sur quelques objets prehis- 



toriques du Portugal fabriques en cuivre. Contmun. Comui. 

 Trab. Geo/., vol ii., pp. 1 19-124, 1888-92. 



(2) Choffat, Paul. Etude stratigraphique et paleontologique 



des terrains jurassiques du Portugal. Le Lias et le Dogger 

 au nord du Tage. Seccao Trab. Geo!., 1880. 



1 Many of the Portuguese memoirs are published both in French and 

 Portuguese. Where a French translation exists, the French alone is 

 quoted here. Purely palseontological works are not included except 

 where it has been found necessary to refer to them. 



