270 HISTORY OF GEOLOGY AND PALEONTOLOGY, 



Dolomite Reefs of South Tyrol, supplies a comprehensive 

 account of this district, and forms the text to the Austrian 

 Geological Survey Maps. 



More recently the Norwegian geologist, Professor Broegger, 

 has drawn a comparison between the rocks of the South Tyrol 

 eruptive area and those of the Christiania area. He demon- 

 strates that Richthofen's " Melaphyre" of the Mulatto mountain 

 is not younger but older than the tourmaline granite, and that 

 altogether the basic eruptions of augite, porphyrite, plagioclase 

 porphyrite, and melaphyres in the Fassa Valley for the most 

 part preceded the intrusion of the granite. Only a few ultra- 

 basic dykes which penetrate the granite at Predazzo are younger 

 than it. Broegger arrives at the conclusion that granite, 

 monzonite, hypersthenite are only the deep-seated equivalents 

 of the Triassic outflows of porphyrites and melaphyres; and 

 his comparison of the Predazzo and Christiania areas leads him 

 to assign a Triassic age to the granite masses at Brixen, and to 

 the tonalite, adamellite, and banatite of the Riesenferner group, 

 the Adamello group, and Cima d'Asta. 



The extinct volcanoes of the Western Isles of Scotland 

 were first described by MacCulloch (ante, p. 113). Ami Boue, 

 in his Geological Essay on Scotland (1820), distinguished very 

 exactly between basaltic sheets and dykes, and described the 

 various volcanic rocks petrographically. Although a student 

 of Jameson, he attached himself to Hutton's party in regard to 

 the origin of basalt, phonolite, trachyte, porphyry, and granite. 



L. A. Necker, the grandson of the great Saussure, travelled 

 in Scotland and the Western Hebrides in 1823, but his account 

 of his journey contained little that was new. The observations 

 of Von Oeynhausen and Von Dechen, published in Karsten's 

 Archiv in 1826, were of some importance for the geology of 

 Skye, Eigg, and Arran. 



In 1850, the Duke of Argyle discovered in the Island of 

 Mull sedimentary beds with flint nodules belonging to the 

 Cretaceous series, and fossil remains of dicotyledonous plants 

 between basaltic flows. The fossils were determined by 

 Edward Forbes to be of Tertiary age; nevertheless the same 

 author referred the basalts of Skye to the Jurassic epoch. 

 In 1 86 1, Sir Archibald Geikie began that brilliant series of 

 researches which extended over a period of thirty-five years, 

 and made the Western Isles of Scotland a classical area for 

 the study of extinct volcanoes. 



