TRANSACTIONS OF SECTION C. 707 



represents the septal area reduced to zero. The node of the fault and the 

 alternation and alteration of throw are due to the eilects of the transverse 

 folding-. 



These transverse folds of different grades, which affect the various layers of 

 the earth-crust differentially, account also for the formation of laccolites, of 

 granitic cores, and of petrological provinces ; and they enable us also to understand 

 many of the more striking phenomena of metamorphism. 



Of the folds of the third order I shall here say nothing ; but I must frankly 

 admit that the primal cause of all this tangential movement and folding stress is 

 still as mysterious to me as ever. I incline to think that it is due to many 

 causes — to tidal action, sedimentation, and many others. I cannot deny, however, 

 that it may be mainly the result of the contraction in diameter of our earth, due 

 to the loss of its original heat into outer space. For everywhere we find evidences 

 of symmetrical crushing of the earth-crust by tangential stresses. Everywhere we 

 find proofs that the various layers of that crust have been affected differentially, 

 and the outer layers have been bent the most. We seem to be dealing not so 

 much with a solid globe as with a globular shell composed of many layers. 



Is it not just possible, after all, that, as others have suggested, our earth is 

 such a hollow shell, or series of concentric shells, on the surface of which gravity 

 is at a maximum, and in whose interior it is practically non-existent ? IMay this 

 not be so, also, in the case of the sun, through whose spot-eddies we possibly look 

 into a hollow interior ? If so, perhaps our present nebulpe may also be hollow 

 shells formed of meteorites, on the surfaces of which shells the fiery spirals we see 

 would be the swirls which answer to the many twisting crustal septa of the earth. 

 Our comets, too, in this case might be elongated ellipsoids, whose visible parts 

 would be merely interference phenomena, or sheets of differential movement. 



In this case we have represented before us to-day the past of our earth as well 

 as its present. Uniformity and Evolution are one. 



Thus from the microscopic septa of the laminre of the geological formations we 

 pass outwards in fact to these moving septa of our globe, marked on the land by 

 our new mountain-chains, and on the shores by our active volcanoes. Thence we 

 sweep, in imagination, to the tiery eddies of the sun, and thence to the glowing 

 swirls of the nebulte ; and so outwards and upwards to that most glorious septum 

 of all the visible creation, the radiant ring of the Milky Way. 



Professor George Darwin, in his Address to the Section of Mathematical and 

 Physical Science at the meeting of the British Association at Birmingham in 1886, 

 with all the courage of genius, and the authority of one of the sons of the prophets, 

 acknowledged that it seems as likely that ' meteorology and geology will pass the 

 word of command to cosmical physics as the converse.' Behind this generous 

 admission I shelter myself. But I feel absolutely confident that, long after the 

 physicists may have swept away these astronomical suggestions as ' the baseless 

 fabric of a vision,' there will still remain in the treasure-house of the geological 

 fold a wealth of abundant material for the use of the mathematician, the physicist, 

 the chemist, the mineralogist, and the astronomer of the deepest interest and of 

 the highest value. 



THURSDAY, AUGUSTS. 

 The following Reports and Papers were read : — 

 1. Report on Photographs of Geological Interest. — See Reports, p. 290. 



2. On the Glacial Distribution of the Biebechite-Etirite of Ailsa Craig. 

 By JosEFH LoMAS, Assoc. Boy. Coll. Science. 



The rock is a granophyre or eurite, and contains the rare blue variety of soda- 

 hornblende, riebeckite. It has been found as a boulder in glacial deyosits by Mr. 

 r. F. Kendall, F.G.S., and the author in the Isle of Man and at Moel-y-Tryfaen ; 



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