Switzerland, a good many years ago; since which time this locality has
become a classic in geological literature, and has called out many
ponderous monographs in German and French by such men as Heim, Schardt,
Lugeon, Rothpletz, and Bertrand. This example, which was first (1870)
called the Glarner Double Fold by Escher and Heim, is now universally
called a nearly flat-lying "thrust fault," in accordance with the
explanations since adopted of similar phenomena elsewhere. Without
obtruding unnecessary technicalities upon my non-professional readers, I
may quote the words of Albert Heim as to the conditions as now
recognized in these parts:

"These flat-lying faults, of which those at Glarus were the first to be
discovered, _are a universal_ _phenomenon_ in the Northern and Central
Alps."[41]

[Footnote 41: "Der Bau der Schweizeralpen," p. 17.]

The favorite method of explaining these conditions has slightly changed
within recent years, as already remarked. For whereas the classic
example at Glarus was at first spoken of as a double fold-in from both
sides toward the Sernf Valley, this is now universally spoken of as a
"thrust fault," with the rocks all pushed one way. Incidentally it may
be noted that this very fact that what was long regarded as two
completely overturned folds is now spoken of as one flat-lying thrust
fault, is _prima facie_ evidence that there is here _no physical proof_
of any real overturning of the strata, such as we do find on a very
small scale in true folded rocks. The latter can usually be measured in
yards, feet, or inches; while in this example at Glarus the area
involved would be measured in many miles, and in some very similar
examples to be presently mentioned from America the measurement could