September 22, 1904] 



NA TURE 



519 



the thickness of the layer which would be produced by the 

 corrugations resulting, and found it far short of that which 

 the existing inequalities would form if levelled down. 'Ihe 

 discovery of a level of no strain within the crust by Mr. 

 Mellard Reade and Dr. Davison further reduced the possible 

 amount uf corrugation. Even a substratum of liquid 

 magma holding water gas in solution would not account 

 for it, and he therefore argued that the substratum was 

 affected by convection currents, which, ascending beneath 

 the oceans, flowed horizontally towards and beneath the 

 continents. 



Mr. J. J. H. Teall discussed the petrological aspect of the 

 general question, and divided the etfects of movements upon 

 rocks into two classes, easily separable, namely, local and 

 regional. The former were confined to the immediate areas 

 of dislocation, while the latter extended over tens or 

 hundreds of square miles. 



Local movements were characterised by fault breccias and 

 mylonites, these being close grained, compact rocks formed 

 by the crushing down of original rocks as in a mill. In 

 some cases there was no crushing, the dykes being con- 

 verted into foliated schists. In respect of regional effects, 

 we have slaty cleavage due to mechanical deformation of 

 extensive tracts of country. Foliation might be due to the 

 original form of crystallisation or to earth movements after 

 consolidation. 



Prof. T. McKenny Hughes thought that lateral pressure, 

 not necessarily horizontal, had produced almost every 

 feature, and that faults were due to compression occasioned 

 by such pressure rather than by extension. 



The folding skin of an apple due to shrinkage of the 

 interior was not wholly comparable to earth folding, for, in 

 the case of the earth, many complex circumstances had to 

 be taken into account. Time was one important point, as 

 well as such forces as molecular deformation, temperature 

 changes, volume and force of crystallisation, and trans- 

 ference of material from one region to another. 



Prof. \V. J. SoUas said that the belts of folding could 

 usually be correlated with the margins of pree.xisting 

 oceans, and those belts of folding which were comparatively 

 superficial must be accounted for by deep-seated causes. 

 The inequality of the present earth was the best guide to 

 former folding. Inequality at the meeting places of oceans 

 and continents, together with sedimentary deposits on the 

 ocean floor, altered the isothermal lines — flattening them out 

 — and so produced stresses and thrusts, which resulted in 

 pushing part of the material seawards. Thus there was a 

 redistribution of pressure, and this produced fluid magmas, 

 with earthquakes and volcanoes resulting. He thought that 

 all this, however, would hardly suffice for the results pro- 

 duced. There must be another cause. The earth was more 

 pear-shaped in the past than it now is by reason of its 

 relation to the moon. Constant deformation towards its 

 present shape produced contraction of the two hemispheres, 

 and thus the .American and Australian beltings or folds 

 were, he thought, accounted for. Deformation of this 

 character produced the same effects as contraction, and the 

 two causes together, he considered, might be enough to 

 account for the existing phenomena produced by earth 

 movements. 



Sir John Evans remarked that thirty years ago he had 

 .irgued that if a globe with a fluid nucleus and a solid crust 

 were postulated, deposition or other causes would result in 

 the solid crust moving over the nucleus, and this disturbance 

 would produce a change in the position of the pole. There 

 was evidence of such a change in the fossil fauna and flora 

 of the Arctic and .-Xntarctic regions. This might be an 

 additional aid beyond those due to cooling. 



Prof. Blake thought that, in speaking of thrusts. Dr. 

 Home had only given the description, and not the cause. 

 In the north of Scotland, where did the force come from? 

 He suggested that if mountains expanded upwards by lateral 

 or upward pressure, a sufficient cause for such thrusts would 

 be found. He had never, he said, seen a true isoclinal fold, 

 and he considered it mathematically impossible for one to 

 exist ; the nearest to it in nature was a pleisioclinal fold. 



Prof. Rothpletz, of Munich, referred to overthrusts he 

 had observed in Saxony twenty-five years ago. The Scotch 

 overthrusts were older than those of the .-Mps. In the Alps 

 the plane of the overthrust got steeper and steeper as it 

 approached Vienna. When the folding was a shortening 



NO. 182 I, VOL. 70] 



of the earth's crust, the overthrust was a shortening too, 

 in another direction. The matter was more difficult of 

 observation in Scotland, as the overthrusts ended in the sea. 



Prof. Boyd Dawkins referred to a case in the Derwent 

 Valley where folding had taken place over level beds, and 

 thought they were not necessarily formed at the root below 

 mountains. 



Prof. J. Milne submitted that the seismologist required 

 a world like that of the physicist, one as rigid as cast iron. 

 Earthquake waves traverse chords of the earth at ii or 

 12 km. a second, i.e. twice as rapid as through steel. This 

 indicates a world very rigid and uniform in the interior. 

 He thought that if it were liquid with convection currents, 

 as urged by Mr. Fisher, the velocity of tremors would not 

 be uniform. 



Dr. Knott advised caution in accepting the abrupt change 

 from solid to liquid as supposed by Prof. SoUas. The 

 changes from solid to liquid would probably be through a 

 viscous condition. 



Prof. Kendall, in winding up the discussion, pointed out 

 that the special feature of continental margins was de- 

 position. Deposits, acting as imperfectly conducting 

 blankets, would cause the isotherms and the critical zone to 

 rise, and the weakest spot would give way. Given stiff rocks 

 above the critical zone and plastic rocks below-, puckering 

 must take place. He considered that in thrust planes the 

 rocks were not forced over horsts, but the horst was wedged 

 underneath them. While areas of sedimentation were weak, 

 other and thinner rocks were stationary under deforming 

 stresses. 



Following the discussion. Prof. Kendall read a paper on 

 the evidence in the Secondary rocks of persistent movement 

 in the Charnian Range, in which he gave specific examples 

 of the movements which had been discussed by previous 

 speakers. He referred to the speculations of Godwin 

 .■\usten, who stated that all recent anticlines are built on 

 older anticlines. 



The Charnwood rocks showed evidence of folding in a 

 N.E. to S.W. direction even before Cambrian times. These 

 movements were continued in pre-Carboniferous, Carbon- 

 iferous, and Permian times, and grounds existed for the 

 belief that they were repeated at intervals during the 

 Jurassic and Cretaceous periods. The Charnian axis, he 

 believes, constitutes the boundary of two important coal 

 fields which extend under the Secondary rocks far to the 

 south. ' J. LOMAS. 



RECENT STUDIES OF DISEASE ORGANISMS. 



A T the recent Cambridge meeting of the British 

 Association, the results of several investigations of 

 organisms associated with various diseases were described 

 before the section of zoology, and are' here summarised 

 separately from the general report of the proceedings of the 

 section, which will appear in another issue of Nature. 



Mr. A. E. Shipley, F.R.S., on behalf of Dr. Elliot 

 Smith, gave a brief account of Looss's observations 

 on Ankylostoma duodenale (miner's worm), and directed 

 attention to the series of preparations sent by Prof. Looss 

 from Cairo illustrative of his recent work. The male and 

 female of this worm are found hanging in numbers to the 

 intestinal walls of the man affected, and produce enormous 

 numbers of eggs, which are discharged from the body. 

 These give rise to small active worm-like larvce which live 

 in mud, and enter the body of man either along with food 

 or through the skin, which they can penetrate without 

 causing any visible lesion of the part. They then enter the 

 lymph- and blood-vessels, are swept into the circulation, 

 and eventually reach the lungs, where they pass from the 

 blood-vessels into the air cavities. From the time the larvae 

 perforate the skin until they reach the lungs they remain 

 the same size, but as soon as they reach the air vesicle they 

 begin to grow rapidly. They pass into the bronchioles, up 

 the bronchi and trachea, and, emerging through the glottis, 

 pass down the oesophagus to the duodenum, where they 

 become sexually mature. The bare-footed races of the 

 tropics and subtropics, both in the Old World and Am.erica, 

 are widely and generally infected with this worm, which 

 produces severe anaemia, often ending in the death of the 

 host. 



