1905] A Landslide on the Lievre River. i«7 



landslip described by Dr. Chalmers was closely simliar to that 

 of the Maskinong-^ river described by Logan. It took place on 

 the east bank of the Blanche, a tributary of the Ste. Anne de la 

 Parade at St. Thuribe, about 3 miles north of St. Casimir village. 

 The chasm remaining from this landslip is also irregularly oblong 

 in shape, like that of the Maskinong6 valley with the narrowest 

 end towards the Riviere Blanche. At this point the breaking 

 down of the beds began and through this opening the whole 

 of the material of the landslip was discharged. The length 

 of the pit, east and west, is about 1,050 yards; extreme 

 width 600 yards; maximum depth about 28 feet ; total area 86 

 acres. The descent of the bottom throughout its whole length is 

 approximately about 27 feet or about 10 inches to the hundred feet, 

 and the gradient is comparatively uniform from the eastern end 

 to the present bottom of the river. Indications of a movement of 

 the clays was first seen on the evening of the 6th ot May, 1898, in 

 a small hollow in the bank, down which a trickling stream ran; 

 but no attention was paid to it. About 5 o'clock on the morning 

 of the 7th, the breaking away of the clay beds began where some 

 slipping had been noticed on the previous evening. The softer 

 material flowed out from beneath, while the upper and more 

 coherent clay split off in vertical sheets and columns which were 

 borne away in the sliding, surging mass. This continued for up- 

 wards of three hours, when the transporting power seemed to have 

 spent itself, and the great masses of clay, which had become detached 

 from the walls of the chasm, were stranded in its bottom and at the 

 time of examination were seen standing in various positions, some 

 of. them resembling cones, pyramids, etc. J 



The causes operating in the production of all these landslips 

 may be summarized under two general headings : — 



I. The presence of silty, sandy, or gravelly portions or layers 

 in these stratified clays, renders these and some of the adjacent 

 portions capable of absorbing and retaining a large amount 

 of water. According to Mr. R. A. A. Johnston, of the Geological 

 Survey, who made an analysis of the clays obtained from the 



lAnn. Rep. Geol. Surv. Can., Vol. XL, 1898. Part J, pp. 05-69. /y^^^^A/ 



