Rev. A. Irving— Bergstiirze,” or “ Landslips.” 161 
strata descended into the sea during the years 1870 and 1871. The 
landslip of Naina Tal is also fresh in the recollection of most of. 
us. It is however in connexion with the Alps that I propose here 
to treat of phenomena of this class. The worn-down stumps of 
ancient mountain-systems which these islands furnish give us only. 
a faint idea of the importance of Bergsttirze in relation to the physi- 
ography of the Alps, which are of comparatively recent elevation. 
In our own language we have scarcely even a vocabulary which 
conveys accurately the meaning of such words as ‘ Bergsturz,’ or 
indicates adequately such modifications of the phenomenon as are 
expressed by the words ‘Schuttrutschung,’ ‘Schuttsturz,’ ‘Felsschlipf,’ 
‘Felssturz.’ For a clearer idea of these Iam greatly indebted to 
the interesting and masterly memoir on them recently compiled by 
Prof. Heim of Ztirich.! From this I extract a few instances, which 
will suffice perhaps to show the important part which Bergstiirze 
have played both in historic and pre-historic times, in forming some 
of the minor features of Alpine valleys. They occur most frequently 
among the stratified deposits of the Alps; and one of the most in- 
teresting facts about them is the part which they have played in 
connexion with valley-lakes.2 As Herr Heim points out, they are 
but extraordinary instances of that general process of degradation 
which is going on in every mountain-range, through the action of 
well-known sub-atmospheric agencies, a process which is going on 
“ day and night, year in year out.” 
Four principal types of Bergstiirze are recognized by H. Heim. 
1. Schutirutschungen.—In such cases vast accumulations of débris 
(‘Schutt’) on the mountain-slope, whether as talus or moraines, 
getting water-logged, descend into the valley. The water increases 
the weight of the mass and at the same time diminishes both the 
internal friction of the constituent parts of the mass and its friction 
against the mountain-side. In some instances, as in that of the 
village of Herdern in Thurgau, the downward movement has been 
arrested in its earlier stages, and much valuable property thereby 
saved: the mass being tapped and its surface drained, sufficient 
friction has been produced to prevent further descent. One of the 
most remarkable instances of this class is perhaps the movement 
which is now going on at the village of Fetan in Unter Engadin. 
Houses are tilted or parted asunder, and the solid rock on which the 
tower of the church stands is found to be but a great mass of granite 
which is slowly moving with the looser materials in which it lies 
imbedded. The slow preliminary movement which precedes the 
final catastrophe, goes on in some cases for years, and is accompanied 
by much friction of the parts against one another, so that the 
contained fragments are often found to be polished (‘spiegelglatt ’) 
and striated in the direction of their descent. This is worth some 
consideration from its simulation of some of the effects of glaciation. 
Minor instances of such earth-movements cited by Herr Heim are 
1 “ Ueber Bergstiirze.’’ 
2 Cf. paper on ‘‘ The Origin of Valley-lakes,’’ by the author, Quart. Journ. Geol. 
Soc. vol. xxxix. part 1. . 
DECADE II.—VOL. X.—NO, IY, it 
