Professor J. W. Judd, C.B. 389 



the fossils of the various berls, and showed the exact age and relations 

 of the "whole series from the Trias to the Upper Oolites. 



The study of the Mesozoic strata of the east coast of Scotland 

 naturally led to the examination of the equivalent beds in the 

 western coasts and islands, and here Judd, in addition to working 

 out minutely the succession of Jurassic and Triassic rocks, was able 

 to show that interesting representatives of the Carboniferous and 

 Oretaceous systems — the presence of which had been hitherto quite 

 unsuspected — actually occur in these Western Highlands. 



The preservation of patches of younger rocks in the west of 

 Scotland, while as in the eastern area partly due to the action of great 

 faults, is to a still greater extent the result of the protection afforded 

 by the vast masses of igneous rocks with which they are associated. 

 ■Judd's attention was therefore soon directed to the unravelling of 

 the complexities of these rock- masses, and of their relations to the 

 Mesozoic strata. The task was at the time one of great difficulty, 

 for no Ordnance Maps of the district had been published, while the 

 facilities for travelling in the district, especially to a man of small 

 means, were far less than even at the present day. 



Macculloch had demonstrated that these igneous rocks are of later 

 date than all the Secondary strata with which they are so closely 

 associated, while Zirkel had proved that among the rocks of Skye 

 true granites and gabbros occur. Other writers, however, bad 

 maintained the Jurassic age and a raetamorphic origin for these 

 rocks. The result of Judd's work was to establish the fact that 

 between the most perfect granites and gabbros there exists every 

 gradation, to rhyolites and pitchstones on the one hand, and to 

 basalts and tachylytes on the other hand ; and thus that the dis- 

 tinction between ' plutonic ' and ' volcanic ' rocks is a purely artificial 

 one. That all these igneous rocks must be of Tertiary age he 

 proved by showing that they overlie and are intrusive in the 

 youngest Cretaceous strata (Chalk of the Zone of Belemnitella 

 mucronata). 



As the result of a general survey of the igneous rook-masses, he 

 was able to state that they indicate the existence of five centres of 

 eruptive activity — the sites of great Tertiary volcanoes ; and that 

 concerning the dimensions and history of these volcanoes im- 

 portant evidence can be obtained ; the extinction of these great 

 volcanoes was shovvn to have been followed by sporadic outbursts 

 all over the area. He maintained that the general order of succession 

 in the eruption of the igneous materials was from the acid to the 

 more basic varieties. 



The results of this work in the Western Isles of Scotland 

 attracted much interest among geologists, and the veterans of the 

 science — Lyell, Darwin, and Scrope — were warm in their praise 

 and kindly in their encouragement and aid. In 1874 Sir Charles 

 Lyell, then nearly blind, invited Judd to spend part of the Summer 

 at his home in Forfarshire and to visit and talk over many of the 

 •scenes of the master's early labours, while helping to revise a new 

 edition of the " Elements of Geology." After the death of Lyell, 



