OEIGIN OF EIVBE TEERACES. 65 



fourth of a mile is a crooked bluff. At one place the bluff makes a very 

 reentrant curve and borders a cirque, locally known as the "Hopper hole." 

 There can be no doubt as to the origin of this bluff. Within a few years 

 preceding 1878 (the date of my visit to the place), the subterranean waters 

 had eroded a ravine 10 to 70 feet deep and had cut back into the plain for 

 300 feet. In spite of the most strenuous efforts to stop the washout in 

 order to save the public road, it had been necessary to change the road 

 twice. Large piles of brush, logs, bowlders, and various kinds of rubbish 

 had been thrown into the ravine. The floAv had at times been tempo- 

 rarily stopped, but the waters collected as behind a dam, and the porous 

 sand and gravel over considerable areas became permeated by water 

 under pressure until a considerable part of the gravel plain was in the 

 semiliquid condition of quicksand. Finally either the dam was swept 

 out of the ravine or the sand-and-gravel plain was washed away around 

 the ends of the dam. When once the sand and gravel was in motion, it 

 passed readily into the river, very little being dropped on the way. The 

 work of the river consisted in carrying away the sediment furnished it by 

 the springs. Here is an unmistakable case of steep cliffs or bluffs of 

 erosion formed at a considerable distance from a river, not by the meander- 

 ing of the river but by rains and boiling springs, the surface wash being- 

 small compared with the action of the subterranean waters. 



The great amount of erosion effected by subterranean waters as they 

 rapidly flow out of a porous mass of sand and gravel has recently been 

 demonstrated at a point 5 or 6 miles northeast from Cherryfield. The site 

 of the washout is at a boiling spring which had long been known to issue 

 from the southern edge of the great glacial sand and gravel plains of 

 Deblois and Columbia. The plain here ends in a steep bhiff facing the 

 south, and rises 50 feet above tlie plain of marine clay at its base. At the 

 time of the washout a ravine 100 feet long, 26 feet wide at its base, and on 

 the average 30 feet deep, had been cut back into the gravel plain, and the 

 eroded matter had been spread over an area of 2 or 3 acres at varying 

 depths up to 4 feet. No surface stream is to be found on the gravel 

 plain near this place, and the cause of the eruption lay beneath the plain. 

 During the winter of 1885-86 there was a thaw, during which a large 

 amount of snow melted. Soon after there came a remarkable storm. The 

 precipitation took the form of snow in the interior of the State, but over a 



MON XXXIV 5 



