368 



DESCRIPTION OF THE 



more fully developed in the gorge, a short distance up the river, some of the beds pre- 

 senting the amygdaloidal form, others the characteristics of the conglomerate. This 

 is particularly well seen between the first and second falls of the river. The lower 

 falls are about forty yards further up, with several small cascades between them. The 

 water falls in that distance seventy-eight feet. At the second falls, the lower beds 

 disintegrate with great facility. At the mouth of the river, an arch has been cut 

 through the amygdaloidal beds, on the left side, through which the river enters the 

 Lake, when its mouth becomes blocked up by sand and gravel during the prevalence 

 of storms, as shown by the sketch on page 367, taken by Dr. Owen, in 1848. 



Between the mouth and the first fall, the conglomerate is overlaid by twenty-five 

 feet of grayish-coloured metamorphosed rock, and above that is a bed of trap, as 

 shown in the following cut. The water falls twenty feet through a gorge eight feet 



c b 



a. Conglomerate. 



b. Metamorphosed 



sedimentary beds. 



c. Basaltic bed. 



in width. The metamorphosed rock gradually assumes a more compact character 

 in the ascending layers, and finally graduates into an amygdaloid like the one 

 underlying the conglomerate. 



One mile up the river, a bed of amygdaloid is overlaid by a very hard, compact 

 rock (No. 211), which presents at some points a semi-columnar structure and a 

 trappous appearance. It is, however, a metamorphosed siliceo-argillaceous shale, 

 and seems to have some intercalated beds of argillaceous sand-rock. About two 

 miles up the river, it forms narrow perpendicular dalles, the walls of which are 

 forty feet in height. I estimated these shales to be two hundred and fifty feet in 

 thickness. They are in layers from half an inch to two inches thick, generally of 

 a red colour, but in some places gray ; the upper part weathering easily, but be- 

 coming more compact in the lower beds, which are of a dark purplish colour, and 

 amygdaloidal. 



Between the brecciated conglomerate and the metamorphosed shale, is a bed of 

 coarse, dark-red trap, from fifteen to twenty feet thick, and conforming to the general 

 dip of the rocks already named, which is southeast by south, at an angle of from 8° 

 to 10°. Above this point, and beneath the trap, there occurs from two hundred 

 and fifty to three hundred feet of a rock such as has usually been described under 

 the name of volcanic breccia (No. 212). At the junction of this rock with a dike 

 which crosses it, it presents every evidence of fusion, and resembles, in both internal 

 and external characters, some of the breccias from extinct volcanoes of Italy and 

 France. It is evident, however, that the great mass of material which enters into 

 its composition, has been derived from sedimentary rocks, through which the molten 

 trap has been forced, breaking them up, and reducing the fragments to a semi-fluid 

 state. Beyond the dike, for the distance of a mile and a half, this rock is exposed 



