108 ON EROSIONS OP THE EARTH'S SURFACE. 



(recently) been submerged in the waters of the ocean. The very entrance to San Francisco bay, has 

 evidently been made by the erosive power of the sea; it being not more than a quarter of a mile in width, 

 with cliffs rising nearly perpendicularly several hundred feet on either side. And .the mouth of the 

 Sacramento river is still less in width, and having similar cliffs of solid stone, through which in time it 

 has worn its way down to its present level. This is where it forms its passage through the coast range 

 of the Sierra Nevada mountains, between which and the interior range lies the valley of the Sacra- 

 mento. This valley is remarkable for its appearance of having once been the bed of an inland sea. 

 You ascend the river some eighty miles from its entrance into the bay, by steamer, and after having 

 passed the coast range, its banks stretch away into the vast level of the plain, with nothing to intercept 

 the view but the tall waving grass and weeds. You then proceed about the same distance by stage to 

 the mountains, and as you are whirled along over an almost level surface of sand, gravel, and marl, 

 occasionally crossing the beds of rivers now dry, you are led to think that where you are now riding 

 leisurely along, the mighty giants of ocean once sported and played. On leaving the valley to ascend 

 the mountains, you see on either hand, stretching away to the north and south, perpendicular cliffs of 

 basaltic rock, and vast columnar palisades, which present every appearance of having once with- 

 stood the action of the waves. On arriving among the mountains, the rocks indicate their volcanic 

 origin, and present a varied and interesting aspect. I never witnessed scenery more grand and terrific 

 thau that on the rivers that flow down the western slope of these mountains. You are walking 

 along over gentle eminences and little vales sprinkled with a thousand various flowers, and crowned 

 with giant pines and cedars, when suddenly your ear catches the faint roar of distant waters, and 

 immediately you are standing upon the brink of a precipice more than two thousand feet in perpen- 

 dicular height, at the base of which you see the river foaming and dashing alpng, over rocks and cliffs, 

 and madly seekiug its way to the far off valley of the Sacramento, the opening to which you can just 

 discern in the distance. Turning your eyes towards the source of the river, you behold the eternally 

 snow-clad summits of the Sierras, peering high amid the clouds, and reflecting the beams of the sun. 

 Opposite to you you see the various rock formations through which the river for numberless years has 

 been cutting its way. Occasionally veins of quartz appear like banks of snow amid augitic and feld- 

 spathic granite, awakening interesting conjectures in the scientific mind. These manifestations of 

 power have an effect of awe and sublimity upon the mind of the beholder, and lead him to wonder and 

 adore the Omnipotent Creator." 



24. Passage of the river, Zaire through the mountains, a distance of 40 miles, in 

 Central Africa. — The width of the stream is from 300 to 500 yards. The channel, 

 everywhere "bristled with rocks" of mica slate, quartz rock, and syenite: in many 

 places they were "stupendous overhanging rocks." — Tuckey's Narrative, pp. 176 

 and 349. 



25. Valley of erosion in the western part of New Fane, in Vermont. — Upon a lofty 

 hill in the west part of New Fane, is an extensive bed of serpentine, associated 

 with soapstone, running nearly north and south. On the west side the hill slopes 

 rapidly towards a small stream, which lies a little over 300 feet below the summit. 

 A similar slope rises on the west side of the brook, extending into Dover. In the 

 soapstone bed, near the top of the hill, are distinct pot-holes, which I regard as 

 decisive evidence that a stream once ran there and formed a cataract. The con- 

 clusion is irresistible that the present stream, or its progenitor, once ran over this 

 spot, and consequently that broad valley has been subsequently worn out. On 

 Plate XII., Fig. 7, I have exhibited this valley with its sides having the slope 

 which was determined by the clinometer. 



This is an instructive case. For if this valley has been the result of river 

 action, one could easily be made to believe that almost any other valley in the 

 mountainous parts of our country had a similar origin. 



