262 THE NATURALIST IN NICARAGUA. [Ch. XIV. 



scratches and grooves are met with wherever the rock 

 surface has been recently laid bare, I do not remember 

 having ever seen any on natural exposures. It is only 

 where protected by a covering of clay or gravel from the 

 action of the elements, that they have been preserved 

 through the ages that have passed since the glacial epoch, 

 and as I did not see any rock surfaces near Depilto that 

 had been recently bared, it is not surprising that, not- 

 withstanding the other proofs of glacial action, I should 

 not have seen any ice scratches or grooves. 



I could no longer withstand the evidence that had 

 been gradually accumulating of the presence of large 

 glaciers in Central America during the glacial period, and 

 these once admitted afforded me a solution of many phe- 

 nomena that had before been inexplicable. The immense 

 ridges of boulder clay between San Rafael and Tales, the 

 long hog-backed hills near Tablason, the great trans- 

 ported boulders two leagues beyond Libertad on the 

 Juigalpa road, and the scarcity of alluvial gold in the 

 valleys of Santo Domingo, could all be easily explained 

 on the supposition that the ice of the glacial period was 

 not confined to extra-tropical lands, but in Central Ame- 

 rica covered all the higher ranges, and descended in 

 great glaciers to at least as low as the line of country 

 now standing at two thousand feet above the sea, and 

 probably much lower. 



In my description of the mines of Santo Domingo I 

 have only briefly alluded to the scarcity of alluvial gold 

 in the valleys. It may be correlated with a similar 

 scarcity in the glaciated valleys of Nova Scotia and 

 North Wales in the neighbourhood of auriferous quartz 

 veins, and is probably due to the same cause. Glacier 



