124 Notices of Memoirs—Prof. M. Bertrand— 
manner. In the region visited by us, in the midst of this maze 
of beds always resembling one another and repeated in narrow 
his plottings on a scale of z>4¢5; not one bed of which Mr. Peach 
could not beforehand tell us the number. 
The arrangement that I have been attempting to describe is 
exactly what Professor Suess has called schuppen-structur (imbricated 
structure), and it is to be seen produced, in the Bernese Jura for 
instance, as a particular case of folds; it is, in fact, the structure 
which one would obtain by imagining a series of folds inclined in 
the same direction and by further supposing that in all these folds 
the half corresponding to the inverted beds had been suppressed. 
What makes the explanation difficult here is the fact that the move- 
ment is localized in the floors of the three stories, that is to say in 
bands of deposits of small thickness; one is at first led, under these 
conditions, to attribute it to the friction due to the masses which 
have been moved. It would be easy to suppose that these bands had 
been plicated by the shearing, as a cloth can be wrinkled by passing 
the hands over its surface, but it is less easy to conceive how these 
folds have been replaced by half-folds, or more exactly how the 
plication can have been replaced by a breaking up into fragments 
accompanied by a uniform uptilting of the successive fragments. 
Without for the present seeking for the meaning and cause of 
each of these complications, a common character becomes dis- 
tinguishable: folds are absent or exist only in a concealed form. 
At least, those that are met with are local accidents which can 
scarcely be appealed to in explaining the whole of the phenomena. 
Schematically one can always refer any movement to a fold of which 
a portion has disappeared; but whereas in the Alps such a dis- 
appearance is always momentary and allows the complete fold to 
reappear at a short distance, in Scotland the disappearance of the 
inverted portions is constant and almost without exception. In the 
one case, the explanation by means of folds is the result of direct 
observation ; in the other it is based on a priori reasoning. The 
difference may be expressed in yet another way: in the Alps the 
suppression of beds is almost always due to sliding parallel to 
the stratification, and I have attempted in a previous article! to 
explain that this was a natural consequence of the parallelism 
between the beds and the forces of compression. In Scotland there 
is the same parallelism and yet the slides, with the exception of the 
three great thrusts, are almost always oblique to the stratification 
of the deposits. For so complete a change there must certainly be 
a general and deep-seated cause. This cause cannot reasonably be 
sought for in the nature of the forces in action; it must therefore 
depend upon the resistances brought into play. A remarkable series 
of experiments by Mr. Cadell, partly carried out with the collabor- 
ation of Mr. Peach, is perhaps such as to throw some light upon 
the question.” 
1 Revue générale des Sciences, f. iii. p. 1. 
? Trans. Royal Soc. Edinburgh, vol. xxxv. part ii. p. 337. 
