82 



NATURE 



[November 24, 1892 



Fig. 9. 



there occurs a deformation, as in the case of lateral pres- 

 sure. Deformation in the first case is greatest near the 

 •obstacle. 



Anticlinal Rupture, Pinch-folds, Squeezing, Pseudo- 

 eruptive Processes. 



Pushing produces compression. In the anticlines 

 tension effects rupture. In the fold-limbs plastic material 

 is squeezed, rolled out, and pushed towards the clines 

 ^syncHnes or anticlines). 



In the synclines of great dimension plastic material is 

 pushed together and pinch-folds result. 



Passing over some of the experiments 

 which illustrate ihe dislocations described 

 by Heim and Margerie we come to more 

 complicated examples. 



Figs. 5-8 show "pinch-folds" in very 

 plastic material, which are spread and thrust 

 over, so that they form a flat bottom in the 

 syncline. 



Other experiments illustrate a pinch-fold 

 with ruptural deformation. Usually the in- 

 tense deformation is confined to the district 

 of the pinch-fold ; in very plastic material 

 -and under variable pressure the stratum 

 in every part gets greatly altered. If we 

 divide the strata into differently coloured 

 prisms we see in each profile at once the 

 deformation at every point. Often defor- 

 mation is so intense that we may denote it 

 .as kneading. 



The deformation shows how a vertical 

 dyke gets influenced by folding. 



If a plastic stratum is inserted between 

 rigid strata, the former often gets injected 

 into ruptures of the rigid sediments; mud- 

 dykes, pseudo-eruptive processes (Reyer, 

 ■" Theoret. Geol." p. 330). 



Movements of Normals and of Waves. 

 Overthrust, Thrustplattes.^ 



In a fold-chain the higher masses are 

 pushed over the lowland, which does not 

 yield sufficiently. The result is an over- 

 thrust, often combined with pinch-folds. Fig. 

 II (exp. 207). The inverted strata dip 

 against the direction of the push. 



Fig. 9 = original thickness of strata. In 

 Fig. 10 folding begins. Fig. 16 last stage. 

 Normal measure at the base=i dm. 



In most cases shifting occurs between the 

 strata, especially in upheaved strata, and we 

 see gaping fractures, which cross a stratum 

 and then follow again the planes of stratifi- 

 ■cation (intrusive sheets). 



The gliding movement may sometimes 

 cause an extrusion. 



Fig. 12 plan, and section Fig. 13 (exp. 278). 



An ovenhrust-fold is nearly squeezed off 

 (compare position of normals). An intense 

 .thrust generates ruptures, and the strata 

 glide in the form of scales over the lowland. 



Fig. 14 (exp. 242) a fault in the base, over 

 which a complex of sediments glides ; the 

 lowland sinks and the higher masses now push with in- 

 creased force towards the plain (" Vorfaltung " : Suess). 



Squeezing and Tearing, Deformation of Included Masses. 



Squeezing and tearing often occur in regions of great 



difference of tension or pressure. In the anticlines 



strata are torn, the direction of ruptures is converging 



'Compare the excellent experiments of Forchhammer (Sanddruck,i883), 

 ■Cadell (.Vature, vol. xxxvii., p. 489). Those authors experimented with 

 powdery material, whereas I operate upon plastic materials. 



NO. 1204, VOL. 47I 



towards the axes (axipetal direction), in the limbs there 

 occur squeezing and tearing. 



[In the latter part of his memoir. Dr. Reyer shows how 

 his experimental methods may be applied to the explana- 

 tion of such complicated questions as very complicated 

 overthrust faults, the appearances presented when much 

 folded and faulted strata are subjected to erosion, the 

 occurrence of undisturbed tracts associated with much 

 folded ones, and the formation of lake-basins.] 



E. Reyer. 



GALILEO GALILEI AND THE APPROACHING 

 CELEBRA TION A T PADUA. 



ALTHOUGH Galileo began his career as a teacher in 

 Pisa, and occupied for three years the Chair of 

 Mathematics there, and was inscribed until his death in 

 the list of the teachers of that University, nevertheless 

 the University of Padua was the one to which from the 

 beginning he had aspired, and in which he exercised with 

 the greatest efficiency his powers as a man of science and 



