406 SCIENCE PROGRESS. 



quina beds, the Jurassic strata being entirely absent at this 

 point, though present to the north and south. The con- 

 clusion forced upon us therefore is, that here we have a 

 remnant of an old continent, or land barrier, which remained 

 when the great depression took place, whose effects are so 

 strongly marked throughout the world. 



Whilst the publication of this work by Professor Suess, 

 with its ingenious blending of ascertained fact and well- 

 balanced hypothesis, opened up a new world of activity in 

 geological thought, the labours of Escher, Baltzer, and Heim 

 were laying the foundations of a new structure which was to 

 celebrate the apotheosis of the fold. Commenced by Baltzer 

 in 1873 with the issue of his paper on the Glarnisch, it was 

 consummated by Heim in 1878 in the publication of the 

 Mechanismus der Gebirgsbildung, with its wealth of detail 

 and beauty of illustration, which gave a new impulse to 

 geotectonic discussion, and influenced deeply many of those 

 geologists who are now taking a front rank in this parti- 

 cular branch of inquiry. 



Professor Heim lays special stress on the importance of 

 foldings in mountain structure. His theory may thus be 

 succinctly set forth. At a certain depth beneath the earth's 

 surface the rocks are loaded far above their power of re- 

 maining solid. This pressure is applied in all directions, so 

 that each individual component is equally affected, and even 

 the most massive rocks are maintained in a state of latent 

 plasticity. Should there now ensue a disturbance of equi- 

 librium through the application of a new force, the horizontal 

 mountain-forming compression, there will be then a me- 

 chanical transformation in the deeper-seated portions without 

 fracture, but nearer the surface in the more massive 

 materials fracture would result. It follows, therefore, from 

 this that all the foldings we see in the Alps have been 

 formed deep in the earth's crust, and the whole of the strata 

 that overlay them have disappeared under the action of 

 denuding and erosive influences. Ordinary faulting is of 

 the rarest occurrence, and the throw rarely exceeds a few 

 metres, and even then the effect is purely superficial. He 

 points out as a matter of fact that in the younger geo- 



