SUBAQUEOUS GLIDINGS 659 



a depth of 125 meters. The affected part of the coast extended 

 from Horgen to Kapfnach, a distance of 1.5 km. The material was 

 spre;ad over the lake bottom, raising it from i to 3 meters. In Oc- 

 tober, 1877, another small portion (the Sustplatz) subsided 

 (Frankfurter Zcitung, Beilage zu No. 304, 1877), showing that 

 movements are not ended. More recent glidings if they occurred 

 have not come to our notice. 



The village of Zug has a similar record. As early as 1435, on 

 March 4th, 26 houses on the "Niederen Gasse," in the old part of 

 the village, slipped into the lake, 60 persons perishing at the time. 

 In 1593 the level of the lake was lowered by drainage, and further 

 subsidences occurred. On July 5, 1887, three successive portions 

 of the shore fell into the lake, submerging more than 20 houses. 

 The material which slid into the sea consisted of sandy mud, a delta 

 built by the Lorze when the lake stood at its higher level. A broad 

 stream of mud flowed into the sea, 300 meters from the point of 

 fracture, to a depth of 23 meters, under the lake level, and then con- 

 tinued outward to a distance of about 1,020 meters from shore and 

 a depth of 45 meters below lake level as a broad mud flow 150 to 

 250 meters wide and from i to 4 meters high. The gliding began 

 in the lakeward region, and migrated landward, as in the case of 

 headward-growing streams. The remarkable fact here is that the 

 average grade of the surface along which the gliding has taken 

 place from the break to the end of the mud stream, a distance of 

 1,020 meters, was only 4.4 per cent. The earlier, smaller move- 

 ment extended for only about 500 meters into the lake and over a 

 grade of 6 per cent. The same rule thus seems to hold for the 

 subaquatic as for the subaerial solifluction, namely, the larger the 

 moving mass tJie smaller the average slope on tvhich it moves. 



]\Iany similar though less instructive glidings have taken place 

 on the Swiss lakes, among them those of Montreux-Veytaux on 

 Lake Geneva (Schardt-85; 86). Nathorst has also described simi- 

 lar subaquatic glidings in Sweden. 



In 1895 or thereabouts movements of this type occurred at 

 Odessa, where several buildings slid into the Black Sea. The dis- 

 tance to which this mass was carried is unknown, but it was on a 

 much larger scale than that at Zug. 



Submarine gUdings of this type are probably common, but no 

 measurements are made of them. Such glidings are often indicated 

 on the steeper slopes by the breaking of the cables. In no case, 

 however, have the magnitude and extent of tiie glidings been ascer- 

 tained, though dislocations by faulting are known (see page 890). 



It is of course evident that material thus sliding down a sub- 



