Charles Lapivorth. 



xxxix 



found one that fitted all the facts obtainable. If he had carried out his 

 intention of returning to Eriboll, the somewhat puzzling statement 

 quoted above would doubtless have been expanded and illustrated. 



In comparing the published work of Lapworth with that of the 

 Geological Survey, one is struck by the fact that Lapworth approaches 

 the subject from what may be called the " fold " point of view, the 

 Survey from the " fault " point of view. Lapworth did not attach much 

 importance to this difference, for in a letter to me dated September 21, 

 1885, he wrote: — "The Survey men have gone beyond me in boldly 

 grasping the idea that the same result can be arrived at quite apart 

 from following the theoretical stages downwards inch by inch and 

 simply asserting that under pressure the rock snaps — like a sheet of ice — ■ 

 flakes or shears in parallel slates which slide over each other. In that I 

 agree, though I reach it from an opposite direction. I hold that over- 

 folds, sigmaclines, overfaults, thrustplanes, are Jiomologous and pass 

 insensibly one into the other ; exactly as the American geologists believe 

 that monoclines and ordinary faults are homologous and pass insensibly 

 one into the other. As under certain conditions (excessive tension and 

 torsion) no monoclines are formed but simply faults ; so under certain 

 opposite conditions (excessive pressure and torsion) no overfolds are 

 formed but simply thrustplanes (my overfaults)." 



J. J. H. T. 



As the distribution of the humble graptolites — " outils qu'il a forges 

 lui-meme et que d'autres eussent d^daignes" — had established world-wide 

 time horizons, and had unravelled directly the mountain structures of the 

 Uplands — and indirectly those of the Highlands — so were these last in their 

 turn to be applied to the tectonics of the broader features of the earth-crust. 



In this, as in his other work, while possessing deep and sympathetic 

 knowledge of the researches of such geologists as Suess, Heim, Bertrand 

 and Eriigger, he held steadily to the views of the mechanics of the earth's 

 crust to which his independent thought had led him. In his view 

 the structure underlying rock complication was the " fold," Hogarth's " line 

 of beauty and grace," sometimes tearing into faults or breaking down into 

 cleavage, and of all dimensions from microscopic to mountainous. Lapworth, 

 in his epoch-making address to Section C of the British Association at 

 Edinburgh, and in later addresses, showed that the continents were but the 

 crests and the oceans but the troughs of great earth-waves, with the septum 

 between the two gentle and inactive, or else abrupt, advancing, and alive. 



The greater continental crests are generally sagged downwards, and the 

 oceanic troughs buckled upwards, at their centres. The " land hemisphere " 

 of the world, with its central sag, the Atlantic, has its counterpart in the 

 hemispheric Pacific depression, the one divided from the other by the greatest 

 septal line of the globe, the " Pacific girdle of fire," " ablaze with volcanoes and 

 creeping with earthquakes." 



