648 Instances of twisted Strata 



TwisfED Strata. — The contortions of the limestone at 

 the fall of the Nant d'Arpenaz, on the road from Geneva to 

 Chamonix, are somewhat remarkable. [Seey%. 7 5. in p. 65 1 .] 

 The rock is a hard dark brown limestone, forming part of a 

 range of secondary cliffs, which rise from 500 ft. to 1000 ft. 

 above the defile which they border. The fall itself is about 

 800 ft. high. The strata bend very regularly ; except [at e and 

 f\ where they appear to have been fractured. — J. R. March, 

 1834". [.J. R. sent with this communication a small neat copy 

 of a sketch carefully taken on the spot ; but as this did not 

 exhibit the stratification so distinctly as one which the Rev. 

 W. B. Clarke has since supplied {fig. 75.), we have only, 

 engraved the latter ; into which we have endeavoured to in- 

 troduce the letters e and^ in the points in which J. R. had, 

 in his own sketch, exhibited them. The following remarks 

 are by Mr. Clarke.] 



Nant * (TArpenaz. — J. R.'s drawing is too indistinct to 

 give an idea of the stratification. The curvature of the 

 strata is a disputed point. Saussure first stated the cir- 

 cumstance ; subsequently, Mr. Bake well has considered the 

 appearances an illusion produced by the cleavage. I am 

 compelled to differ from him, and to adhere to Saussure; 

 who mentions that the strata, being originally horizontal, are 

 bent upwards, and then curved backwards. (See Bakewell's 

 Travels, vol. i. p. 339.) In the year 1825, I spent two days, 

 in July, in examining the whole of the strata on both sides of 

 the Nant d'Arpenaz, and, in fact, all that side of the Valley 

 of Maglanz from CI use to St. Martin ; and I confess that 

 there are so many instances of contorted and perpendicular 

 strata in the limestone, that I came to the conclusion that the 

 rocks at Arpenaz, as well as at Nant d'Orli, are merely por- 

 tions of a great range of strata, which, owing to vast pressure 

 and elevation of the subjacent beds, have been forced out of 

 their horizontal position, f The falls, in both instances, rush 

 over the face of the rock ; where there is, evidently, a fissure, 

 apparently caused by a crack upwards through the cliffs. 

 The real curves in the beds are explained in the appended 

 diagrams, which were made in 1825. 



* Kant^ in the language of the country, means a waterfall. 



f The following passage is also corroborative of Saussure's opinion 

 upon the subject : — *' Ein schones vielfaches Echo empfangt hier den 

 Reisenden ; weiterhin stiirzt ihm zur Seite von einer Hohe von 800 Fuss 

 der Gebirgstrom Arpenas {Nant (TArpenaz) als Wasserfall herab, der auch 

 bei geringerer Wasserf iille eins der sonderbarsten Schauspiele giebt, weil 

 die gewaltige Felsenmasse, liber die er hinabstiirzt, eine concentrische 

 Schichtenhildimg hat, die auf das deutlichste in die Augen springt, wie 

 Schaalen, die sich um einen gemeinsamen Kern aufsetzen, und zu bedeu- 

 tender Hohe in S-formiger Gestalt sich emporiu'mdcn^^ (Ritter's Beschrei- 

 buiigzu Kummer's Stereoramades Monlhlanc-Gebirges, Berlin, 1824, p. 31.) 



