260 THE NATURALIST IN NICARAGUA. [Ch. XIV. 



unstratified deposits consist mostly of quartz sand with 

 numerous angular and subangular blocks of quartz and 

 talcose schist. Many of the boulders are very large, and 

 in some parts great numbers have been accumulated in 

 the bed of the river by the washing away of the smaller 

 stones and sand. Some of these huge boulders were 

 fifteen feet across, the largest of them lying in the bed of 

 the river two miles below Depilto. Most of them were 

 of the Depilto quartz rock and gneiss, and I saw many in 

 the unstratified gravel near Ocotal fully eight miles from 

 their parent rock. Near Ocotal this unstratified forma- 

 tion is nearly level, excepting where worn into deep 

 gulches by the existing streams. The river has cut 

 through to a depth of over two hundred feet, and there 

 are long precipices of it on both sides, similar to those 

 near streams in the north of England that cut through 

 thick beds of boulder clav. 



/ 



The evidences of glacial action between Depilto and 

 Ocotal were, with one exception, as clear as in any 

 Welsh or Highland valley. There were the same 

 rounded and smoothed masses of rock, the same moraine- 

 like accumulations of unstratified sand and gravel, the 

 same transported boulders that could be traced to their 

 parent rocks several miles distant. The single excep- 

 tion was, I am convinced, one of observation and not one 

 of fact, viz., I saw no glacial scratches on the rocks ; but 

 geologists know how rare these are on natural exposures 

 in districts that have certainly been glaciated, and will 

 not be surprised that in a hurried visit of only a few 

 hours I should not have discovered any. Glacial scratches 

 are seldom preserved on rock surfaces exposed to the 

 action of the elements. Even in Nova Scotia, where 



