226 



NA TURE 



[July 7, 1892 



under water, gets elevated, it emerges ; the masses are 

 shaken slightly and glide over the inclined base. Fold- 

 ing succeeds, as Figs. 3 and 4 show. 



Fig. 5. 



In Fig. 5 the strata, gliding over the inclined plane to 

 the left, were divided by vertical lines. Distance of lines 

 = 01 metre. At the top of the figure the fixed scale is 



little, the parts near the surface have a higher velocity, so 

 that the vertical lines of division get curved. The motion 

 being intense in the highland (at the right hand), the 

 vertical lines in this region are pushed over and assume 

 a flat position. 



The surface of the gliding masses in this case remained 

 level, as the material was very plastic ; yet folding in the 

 depth of the masses is remarkable. We see that a fold 

 chain may have a wide surface ; the intensely folded 

 regions get exposed only after an extensive erosion or 

 abrasion occurred. This experiment shows also how the 

 motion and the amount of folding decrease in the direc- 

 tion towards the base. 



Figs. 6 and 7 illustrate my conception of the process of 

 glide-folding as it occurs in nature. The black parts form 

 the solid basement ; at S we observe a fault scarp (the 

 coast of a continent). In the sea the sediments sx are 

 deposited. Warming of the newly-deposited masses, and 

 of the lower parts of the earth's crust, in course of time 

 elevates the sediments, as the dotted line in Fig. 6 notes. 

 The sediments glide over the inclined plane towards the 

 right, and form a fold-chain, O. 



The motion of a single point is noted in Fig. 8. Point 

 S first gets elevated (through thermal intumescence) to s', 

 and then it glides towards s". In most cases the 

 way described by a point is complicated, as Fig. 9 illus- 

 trates. Elevation having reached a certain degree, the 

 masses glide a little, elevation continues, again gliding 

 succeeds, and so on. 



Fio. 9. 



noted.^. Point 40a of the strata originally lay directly i The highland in the back of the fold- chain (black mass 

 below jhe scale-point 40, 60*2 was placed below 60, and ! at the left hand) gets eroded ; cooling causes a subsidence 

 so on.^ i of this region, the earth's crust breaks, and through the 



We see at once the amount of horizontal (gliding) 

 movement. The vertical lines are deformed in the 

 direction of the motion. The parts near the base move 



NO. I 184, VOL. 46] 



fissures and faults, in many cases, eruptive material 

 escapes. A volcanic chain is built up in the back of the 

 fold-chain (Fig. 10). In course of time the fold-chain 



