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Before referring to the event of July it may be well to glance at 

 the general contour of the surrounding country. The Lake of Zug, 

 which has an elevation above the sea of 1,368 feet, and a depth of 

 about 1,300 feet, is at its upper and southern end hemmed in by the 

 Eigi and tlie Rossberg, which are separated by the low pass, by 

 means of which the St. Gothard railway is enabled to avoid some 

 of the engineering difficulties that the bizarre outline of the Lake 

 of Lucerne presented. From this low pass and from the northern 

 slopes of the Rigi, and from the western slopes of the Rossberg a 

 series of small streams send down their waters to the Lake, but 

 the quantity is not large. The greater part comes from the 

 northern slopes of the Rossberg, and after passing through th£ 

 Egeri See, takes a northerly direction till it passes the hills that 

 bound the Lake of Zug on the east, when turning to the west and 

 then to the south-west it falls into the Lake very near its outlet. 

 In the latter part of its course it traverses a very level tract of 

 country, the result apparently of fluvial detritus. 



The Rigi and the Rossberg have not contributed largely 

 towards the filling up the Lake of Zug — the alluvial tract at the 

 head of the Lake being of small extent. But they have given us 

 some striking examples of landslips on a large scale. They are 

 both mainly composed of beds of conglomerate (Nagelfluh) 

 consisting of calcareous and silicious pebbles cemented together 

 by a calcareous infiltration, which has bound the whole into a 

 concrete mass, so firm that very often the compacted pebbles will 

 break across rather than quit the mass. These beds of conglome- 

 arate are separated by beds of sand and clay, and anything that 

 seriously disturbs these beds has a tendency to alter the relation 

 in which they stand towards each other. Hence changes have 

 taken place from time to time, and within the last hundred years 

 two very notable events of this kind have happened. In 1795 

 there issued from below some of the upper strata of the Eigi, a 

 vast outflow of mud, which, like a stream of lava, rolled down the 

 mountain side, spreading ruin and desolation in its course. It is 



