640 REVIEWS 



level surface into which the river Vaerdal has cut a steep-sided valley 

 is an upland of stratified marine clays, deposited during a submergence 

 of the Norway coast since the Glacial Period. Within these clays was 

 a great mass of "quick clay" not constituting a definite stratum but 

 existing, probably, in more or less definite lenticular masses. A small 

 side stream, the Folio, had cut a short gorge into the quick clays, giv- 

 ing the latter an exit to the main valley. On the night of the 19th of 

 May, 1893, a volume of this semi-fluid clay, estimated at 55 million 

 cubic meters, escaped into the larger valley, inundating it to the extent 

 of eight and one half square kilometers. The collapse occupied one 

 half hour and the advancing front of the mud traveled five or six kilo- 

 meters in three quarters of an hour. Some of the inhabitants were 

 rescued from the roof of their house after sailing three and a half 

 miles on the river of mud. Over a part of the area the upper layer 

 of clay was firm, and, with the overlying turf, constituted a crust suf- 

 ficiently strong to remain intact while the quick clay flowed out from 

 beneath. Parts of fields bearing trees were thus dropped vertically 

 downward, leaving the trees standing erect at the lower level. The 

 vertical distance through which the surface fell is not given, but the 

 pictures represent it as many meters and the sides of the pit as quite 

 sheer in many places. The author gives a note, also, on a similar 

 but smaller landslip which occurred on the i6th of August of the same 

 year in the valley of the small stream Graaelven. The finely banded 

 marine clays concerned in this slip are made the basis of a time esti- 

 mate. Their thickness is taken at fifty meters, and they consist of 

 alternating dark and light layers. On the supposition that one dark 

 layer and an adjacent light layer were deposited in one year, the time 

 consumed in their deposition is estimated at 4,000 years. The propor- 

 tion of post-glacial time which this represents is not estimated. 



N. M. F. 



Geological Map of West Virginia. Second edition. I. C. White, 

 State Geologist. Published by West Virginia Geological 

 Survey, Morgantown, W. Va. 



The Geological Map of West Virginia, first published in 1899, has 

 recently been revised and new features added. The map shows in 

 separate colors the three great coal formations of West Virginia, viz., 

 the New River or Pocahontas, the lowest; the Allegheny-Kanawha 



