1G5 



ON THE TorOGllArilY AND CEOI.OGY 



other continuing south commences at once to ascend the hill. For some distance it 

 continues over rolling ground, past one or two groups of houses, and then suddenly 

 climbs a steep ascent to the summit of the range. At the base of the hills where the 

 trail first leaves the valley there is a little exposure in the bed of a rivulet where the 

 sandstone beds near the bottom of the series stand vertically. On ascending the hill 

 we find more modern strata coming in, although the shale is but poorly represented, 

 its place being taken by their bedded sandstones. These first dip at very high angles 

 to the south, but gradually assume lower dips, and the higher one climbs the hill the 

 lower he finds, the dip of the strata, until near the summit the limestone is found 

 capping the hill and. dipping southward at low angles. I was not able to measure it 

 with certainty, but it is not far from 20°. The limestone shows only its edge on the 

 north face of the mountain, and although it is unusually compact, differs in no other 

 important respect from the same beds elsewhere. On the south flice of the range it 

 is cut through by the stream along which the road runs," and near the base it is seen 

 to be underlaid again by the same rocks as on the north side.* Beyond the base of 

 the hill a long gradual slope of gravel, the wash from the arroyo, borders the valley 

 and is, as usual in this region, densely overgrown with cactus and acacias. The high 

 angle to which the sandstones are uptilted on the north side of the mountain, while 

 unusual in this range, is not entii'ely peculiar ; nor does the disturbance necessarily 

 extend to a gi'eat distance. A similar upheaval will be described north of Moca which 

 not only does not affect either side of the range greatly, but is actually reversed in 

 both the adjoining sections. 



The next pass east of the one just described is the one most travelled in crossing 

 the mountains. It begins nine miles west of Santiago, at Limon, crosses the range 

 west of the high peak of Diego Campo, and passing Alta Mira and the head-waters 

 of the Isabella River, crosses the lower spur on which is perched Mount Isabella de 

 Torres, and descends to the plain near Puerto Plata. Its entire length, including the 

 nine miles in the valley, is forty-one iniles, and the thirty miles of mountain section 

 is one of the most interesting in the chain. ^ea.v the base of the mountain in the 

 canon of the Limon Creek it is evident that there has been some disturbance even 

 where the surface configuration does not indicate it. While the shales in the valley 

 are usually undulated, dipping in all directions at angles of from 5° to 10° ; here they 

 suddenly pitch northward as high as from 30° to 50°, and bring to the surface the 



* I desire particularly to call the attention of the reader to ray section along this route and then to the section 

 {Qua7't. Journ. Geol. Soc. 1853, %>. 112, fig. 3) of Mount Murass which immediately adjoins the road or its east side, 

 and ■which of necessity must have identically the same structure. Beds No. 10 and No. 1 of that section are in 

 reality identical ; Nos. 2 and 3 are the equivalents of No. 9, which shall he under instead of over No. 10 ; Nos. 4 and 

 5 equal No. 11 ; and the No. 10 on the north tlank does not exist ! 



