76 BULLETIN OF THE ESSEX INSTITUTE. 



in the classification of glacial deposits," based upon a study 

 of the glacial deposits in this field. 



THE WASH-PLAINS OF EXISTING GLACIERS. 



Existing glaciers present two general types of wash 

 plains which may be briefly de8cril)ed as follows. First, 

 in the case of valley glaciers, where the ice front com- 

 monly rests upon a slope high above base-level, the gravel 

 and sand washed out from the ice accumulate in a sheet 

 or fan below the base of the ice. Such is the case with 

 the del)ris washed out from the glaciers of Chamonix in 

 France. It is a characteristic of glaciation in a mountain- 

 ous or upland region. 



Where the ice spreads out on the lowland, we have the 

 second case, in which, owing to delta building in lakes or 

 the sea or upon a plain, the wash accumulates in front 

 of the ice as a fan of gentle slope banking up against the 

 ice margin. 



Probably in all cases where the term plain is used, the 

 form is that of a fan or a group of fans ; and from these 

 almost level-topped deltas to steeper sloping deposits and 

 to cones there is a gradual passage. The term plains is 

 thus only roughly correct when applied to the group of 

 deltas which have accumulated at the ice-front. 



This second group of deposits is found to-day in pro- 

 cess of formation only in high latitudes. Examples are 

 here cited for comparison with New England cases. 



The Heard Island wash-plain. — A graphic account of 

 an outwash plain now in process of formation is given by 

 the late Canon Moseley in his description of Heard Island 

 at the time of the visit by the Challenger. Heard Island 

 lies in about lat. 53° 10' S., and long. 73° 31' E. The 

 following is abstracted from Moseley's account :i 



1 Notes by a Naturalist, made during the Voyage of the Challenger. Revised 

 ed., New York and London,1892, pp. 191-192. 



