538 THE DISTRIBUTION, ETC., OF ALKALINE ROOKS, 



axis of Post-Cretaceous age (see Geol. Map of Portugal), and 

 although no direct evidence of age has been found except that it 

 is newer than the Culm, it seems to the writer that it may even 

 be as late as early Tertiary. Further, Archa3an rocks form the 

 backbone of the Iberian Peninsula. 



4. Kola Peninsula, Finland. — A very interesting mass of 

 foyaitic rock has been described by Hackmann and Ramsay from 

 Umptek, Kola * 



5. Tyrol Area.f — The Tyrol igneous rocks are of Mesozoic age. 

 The earliest probably belong to the late Triassic period. Brogger 

 has shown that the following succession obtained: — 



(1) Camptonite and liebnerite porphyry. 



(2) Granitite (Predazzo and Cima d'Asta). 



(3) Tonalite, banatite and adamellite. 



(4) Monzonite. 



(5) Gabbrodiabase, pyroxenite, augite porphyrite, mandelstein, 

 and tuffs. 



After a careful perusal of Brogger's investigations it seems to 

 me quite feasible that (1) and (2) are differentiation-products of 

 one and the same calcic magma, and (3) and (4) mixtures of (2) 

 and (1) with sedimentary rock which the intrusive rock fused up 

 and assimilated in a deepseated magmatic reservoir. The first 

 two were expelled from the reservoir before assimilation had pro- 

 gressed far, the third and fourth after long stoping, and the last 

 after the acidic portion of the mixture had consolidated. 



The monzonites and tonalites are not true alkaline rocks, but 

 are here referred to as they form a link between the calcic and 

 alkaline. 



The Tyrol mass occupies the position of a senkungsfeld or 

 subsidence-area. 



6. Mittelgebirge of Bohemia. — J. L. HibschJ found the follow- 

 ing succession in alkaline rocks of Tertiary age ; — 



* Founia, B.ii, No.2, Der Nephelin-Syenit der Umptek. 

 t Brogger, Die Eruptivgesteine des Christiania Gebiets, Vol. ii. 

 X See Sonderabdr. aus den Sitzungsber. d. deutsch. natur. medicin. 

 Vereins von Bbhmen. " Lotos" 1897, No.l. Quoted from Brogger. Vol.iii. 



