5i8 



NA TURE 



[September 22, 1904 



glaciation of the Don and Dearne Valleys, sought to extend 

 the system of glacier lakes and overflows of the Cleveland 

 area further south, and in another paper dealing with river 

 capture in the Don system he explained the present con- 

 dition of the Don and its tributaries as resulting from a 

 series of river captures due to the deep cutting of its valley 

 by the Sheaf, and its predominant power in capturing con- 

 sequent streams north and south. 



Other papers dealing with Glacial and post-Glacial 

 geology were read by the Rev. Dr. A. Irving, on stratified 

 high-level gravels and their relation to the Boulder-clay ; 

 by Mr. A. W. Gibb, on the occurrence of pebbles of white 

 chalk in Aberdeenshire Clay : the Rev. O. Fisher, on an 

 elephant trench at Dewlish, Dorset ; Mr. H. N. Davies, on 

 the discovery of human remains under Stalagmite in Cough's 

 Cave, Cheddar ; and reports of committees were read on 

 Irish caves, tidal action in the River Mersey, and under- 

 ground waters of north-west Yorkshire. 



On the day devoted to palaeontology. Prof. Sollas gave 

 an account of his new method of examining fossils by means 

 of serial sections and their reconstruction by means of wax 

 models. In this way he contrasted the structure of 

 Ophiurids of recent and fossil types. 



The finding of Holoptychius scales in the Cornstones of 

 Salisbury Crag has led Drs. Home and Peach to regard 

 some of the beds occurring near Edinburgh, and hitherto 

 thought to be of Carboniferous age, as belonging to the 

 Old Red Sandstone period. Dr. Home described the beds, 

 and exhibited a revised map of the district. Dr. Traquair 

 dealt with the fish remains found in the above deposits, and 

 then read a paper on the fauna of the Upper Old Red Sand- 

 stone of the Moray Firth area, in which he summarised the 

 results of many years' work. 



Mr. G. W. Lamplugh directed attention to the fact that 

 many of the phosphatic casts of fossils found in the Lower 

 Cretaceous rocks at Upware, Potton, and Brickhill, and 

 usually regarded as derivative, really are indigenous. At 

 Speeton and in Lincolnshire these same fossils are found 

 at their proper horizons, and indicate the life of the period. 

 In another paper Mr. Lamplugh showed,' by means of the 

 marine fossils from the Ironstones of Shotover Hill, that 

 the Ironstone originated through the alteration of a band 

 of Portland Limestone. 



Mr. E. A. Newell Arber, discussing the fossil plants of 

 the Upper Culm .VIeasures of Devon, concludes that the flora 

 indicates an Upper Carboniferous age, and the coal-bearing 

 beds of the Bideford district are the equivalents of the Middle 

 Coal-measures elsewhere in Britain — a higher horizon than 

 has previously been assigned to these beds. 



In the same measures, too, he has found mineralised 

 plant remains in the form of rolled fragments of stems, 

 arranged without order in a fine grained sandstone. These 

 are not contemporaneous with the sandstone. 



The committee on the life zones in the British Carbon- 

 iferous rocks reported investigations made in the Culm 

 Measures of North Devon, the Pendleside series of the 

 Derwent Valley, Derbyshire, the North Staffordshire Coal- 

 field, and in South Wales. 



The second report of the committee on the fauna and 

 flora of the Trias included an elaborate description of 

 rhyncosauroid and chelonoid footprints, beautifully illus- 

 trated by photographs by Mr. H. C. Beasley, and lists of 

 Triassic fossils in the Jermyn Street and British Museums 

 by Mr. E. T. Newton and Dr. A. Smith Woodward. 



Prof. H. G. Seeley exhibited and described fossil foot- 

 prints of reptiles from the Stormberg beds of the Karroo 

 of Cape Colony. 



In petrology and mineralogy eight papers were read. 

 One, by Prof. H. Backstrom, was of great interest as 

 showing that the great iron ore deposits of Lappland have 

 been brought up by volcanic agency from great depths. 



Mr. .-\. Harker exhibited a series of Tertiary Plutonic 

 rocks (including gneisses) from the Isle of Rum. He de- 

 scribed the characters and distribution of the earlier ultra- 

 basic group. Into these eucrite has been intruded, and later 

 an acid magma. The complex was then streaked out by 

 movement, and well banded gneisses of the Lewisian type 

 were formed. 



Mr. E. Greenly suggested that the recent lava-pyramid 

 formed on Mont PeMe might afford a clue to the origin of 

 the lava domes of the Eifel. 



Prof. H. A. Miers, dealing with the occurrence of gold 

 in pyrites crystals, showed that in the Urals fresh crystals 

 contained the gold uniformly disseminated, whereas on 

 weathering into limonite the gold formed a nugget in the 

 middle with crystalline facets. As other examples of con- 

 centration due to the attractive forces of crystallisation, he 

 cited gypsum in clay, marcasite, pyrites, barytes, and 

 phosphatic nodules. 



Mr. Lamplugh, in the discussion which followed, remarked 

 that the "dead earth is alive all the time," and gave 

 instances where the formation of nodules has crushed the 

 surrounding shales. 



The basic patches occurring in the Mount Sorrel Granite, 

 according to Mr. R. H. Rastall, are all inclusions of foreign 

 material, and are not the result of concretionary action. 



Papers were also read on the different modifications of 

 zircon by Mr. L. J. Spencer, and on three new minerals 

 and curious crystals of blende from the Binnenthal by Mr. 

 R. H. Solly. 



The granite from Gready in Cornwall was described by 

 Prof. K. Busz. 



The geology of the Oban Hills, Southern Nigeria, by 

 Mr. J. Parkinson, and the report of the committee on 

 geological photographs, complete the list of papers read 

 in Section C, with the exception of a paper by Prof. Kendall 

 on evidence in the Secondary rocks of persistent movement 

 in the Charnian Range, and the discussion on the nature 

 and origin of earth movements, an account of which is sub- 

 joined. 



NO. 182 I, VOL. 70] 



Discussion on the Nature and Origin of Earth Movements. 



The president, in introducing the subject, which proved 

 to be one of the most attractive features of the section, 

 observed that movements of the earth's crust manifesting 

 themselves in the fracturing, overthrusting, and folding of 

 strata had been in operation from the earliest to the latest 

 geological periods, and though intermittent so far as any 

 one region was concerned, there was reason to believe 

 that they had been more or less continuously in action 

 throughout the world as a whole. Their operations, in fact, 

 were essential to the existence of land surfaces, for in their 

 absence all rocks projecting above the sea would be worn 

 away, and the globe would be enveloped in one continuous 

 ocean. Notwithstanding these facts, no theory as to the 

 cause of the movements has commanded universal accept- 

 ance. 



While some hold that the shrinking of the globe by cool- 

 ing and the efforts of the crust to adapt itself to the shrink- 

 ing interior are the prime causes, others maintain that the 

 scale on which folding and overthrusting in the crust have 

 taken place is out of all proportion to the shrinking that 

 can be attributed to such a cause. 



Earth movements may be divided into two principal 

 classes, namely, movements of expansion, which are 

 evidenced by normal faulting, and movements of com- 

 pression, such as are indicated by buckling, overthrusting, 

 and shearing of strata, by the superinduced structures of 

 cleavage and schistosity, and by the extrusion of granitic 

 rocks and metamorphism. 



Dr. Home presented the evidence he had accumulated 

 from observations in the north-west Highlands, and traced 

 the types of movement from the unaltered areas to the areas 

 showing the greatest disturbance of all, namely, the Moine 

 schists. In one region the Moine schists have been pushed 

 ten miles to the west, and are seen lying on undisturbed 

 Cambrian Limestone. Some of the movements undoubtedly 

 occurred in pre-Torridonian times, others succeeded almost 

 up to the Devonian period. 



The veteran geologist, the Rev. Osmond Fisher, said he 

 used to think that the corrugations of the earth's crust were 

 due to compression through the shrinking of the interior. 

 To judge of the sufficiency of this cause, the first thing to 

 be done was to seek a measure of the compression, and 

 then compare the result of the effects of cooling with the 

 actual amount of compression. The most satisfactory 

 measure appeared to be the thickness of the layer which 

 the corrugations would form if levelled down. In 1863 Lord 

 Kelvin formulated a law of secular cooling upon the hypo- 

 thesis of a solid interior. Adopting a probable value for 

 the contraction of rocks in cooling, Mr. Fisher calculated 



