ixXX PROCEEDINGS OF THE GEOLOGICAL SOCIETY, [vol. lxxiv, 



of special metamorphism along faults and overthrusts and in the 

 cores of small anticlines. In some cases the thermal element is 

 much more in evidence than the dynamic, shearing stress having 

 apparently been effectively relieved before the recrystallization of 

 the rocks. Some of Gosselet's ' corneites ' indeed are identical with 

 t} r pes of ' hornfels ' familiar to us in metamorphic aureoles. Our 

 own country too affords examples of metamorphism of a more or 

 less high grade localized in evident relation with tectonic accidents. 

 The belt of maximum metamorphism in the Isle of Man follows 

 a horizon of special mechanical disturbance, and seems to be strictly 

 comparable with some cases in the Ardenne. It is. however, in 

 crystalline rocks, which offer more resistance to crushing, that 

 we should rather look for effects depending upon the mechanical 

 generation of heat. Some special features of the Lewisian tract in 

 the North- West might be cited, and especially the sharply bounded 

 ^east-and-west belts of reconstruction which traverse the old gneiss 

 and its dykes in common. The}' are evidently bound up with 

 displacements of the nature of ' tear-faults,' at some epoch between 

 Archaean and Torridonian. 



To some geologists, whose concern has been with wide tracts of 

 crystalline schists and gneisses, these minor incidents may seem 

 to have little significance; but it is my main thesis that meta- 

 morphism, in all its manifestations, is to be envisaged as a single 

 problem, though a very intricate one: namely, the reconstitution of 

 rock-masses under varying conditions of temperature and stress. 

 To the solution of this general problem data of a large and of a 

 small order may equally contribute, and each will have value in 

 proportion as it tends to bring the facts of observation into touch 

 with known physical principles. 



I now relinquish the office which I have been privileged to hold 

 for two years. Thanks to the consideration which I have at all 

 times received, my tenure of it has been not only an honour warmly 

 appreciated, but a pleasant memory to be cherished. My path has 

 been made smooth by the forethought and promptitude of my 

 fellow-officers and the lo} r al support of the Council. To all these 

 I wish to record my thanks ; as also to the permanent officials of 

 the Society, whose help has always been zealously rendered despite 

 many difficulties incident to these troublous times. You have 

 chosen as my successor one whose high qualifications, both as a 

 geologist and as a man of affairs, are well known to all, and into 

 his capable hands I confidently resign my trust. 



