Ch. XIV.] THE LAUREXTIAN FORMATION. 259 



at the mouth of one of the old shafts. Our guide told us 

 that the lode was two feet wide. Both it and the con- 

 taining rock was very hard, and the miners had also water 

 to contend against. I do not think from what I saw that 

 the mine could be made to pay on a large scale, though 

 next the surface small remunerative deposits of ore had 

 been found. In depth the hardness of the rocks would 

 make the sinking of shafts and driving of levels, the 

 " dead work " of the miners, very costly. 



We started on our return clown the valley at three 

 o'clock, and took particular note of the succession of the 

 rocks, as I had become much interested in finding 

 these quartz and gneissoid beds, which I had no doubt 

 were the same Laurentian rocks that I had seen in 

 Canada and Brazil, the very backbone of the continent, 

 ribbing America from Patagonia to the Canadas the 

 fundamental gneiss which is covered in other parts 

 of Central America that I had visited, by strata of much 

 more recent origin. Going down the valley of the 

 Depilto the massive beds of quartz and gneiss are soon 

 succeeded by overlying, highly inclined, and contorted 

 schists, and as far as where the road from Ocotal to 

 Totagalpa crosses the river, the exposures of bed rock 

 were invariably these contorted schists, with many small 

 veins of quartz running between the lamina of the rock. 

 On the banks of the river, from about a mile below 

 Depilto, unstratified beds of gravel are exposed in nu- 

 merous natural sections. These beds deepen as the 

 river is descended, until at Ocotal they reach a thickness 

 of between two and three hundred feet, and the undu- 

 lating plain on which Ocotal is built is seen in sections 

 near the river to be composed entirely of them. These 



