The Penaebach tunnel is the only one in England that is self-supporting. It is driven through solid basalt. The Penmaenwhr tunnel, pierced through hard green-stone, had to be lined throughout; and the Bangor tunnel, supposed to be sufficiently firm, was afterward cased with brick. It has been found necessary to line some of the tunnels of the Washington aqueduct, which are driven through very hard gneiss.
Before taking leave of this instructive report, we have selected some interesting portions of the narrative and scientific statements for quotation:
“The great falls of the Hingador are grand and exceedingly romantic, and equal in height and beauty to many of those in other countries which elicit so much admiration from all lovers of magnificent scenery. The valley itself is pleasant to gaze upon; many bright streams gush into it, and impart additional charms to the already picturesque landscape of falls and rapids, and rich tropical vegetation. Several thermal springs were discovered at the foot of the great falls.
“As the party had to wade through the water, over smooth and slippery rocks, and clamber up steep precipices, it took four days to accomplish this section of the survey. Several fragments of rocks were broken off at the head of the falls for subsequent analysis. According to the report of the geologist, of which the following is an extract, ‘the rocky falls were found to be overcoated with a light, shaly conglomerate of a cemented texture, and containing, imbedded in a calcareous matrix, coarse sand and gravel. Higher up, in one of the western head branches of this stream, a more consolidated semi-rock was noticed, containing copiously interspersed fragments of little shells. This rock seems also to be impregnated with carbonate of lime.’”
The character of the natives may be gathered from the extract: “January 30th, 1858—Whilst seated on the rocks overlooking the falls, and listening to the music of the roaring waters, as they rushed fiercely past, with an occasional anxious glance at the curve of the river above, in expectancy of the momentary appearance of the long-expected canoe, the attention was suddenly drawn toward a long line of Indians, men, women, and children, emerging from the trail over the Sierra. As they filed by, several familiar faces were seen, and a kindly nod of recognition given and returned. Each bore a pack, from the largest to the smallest; these rested upon the back, and were supported by bands, composed of the bark of trees, which passed in front of the forehead. Most of their effects were packed away in baskets, made of bark of certain trees, and very neatly manufactured. They proved to be old friends from Tocame, and were _en route_ to make a visit to one of their Tambos, on the Nercua. All fear as to moving ahead was dispelled at sight of them. After depositing their loads on the rocks, near the small haven, just above the falls, they all left again as quietly as they had come, in order to bring up their canoes over the Saltos.