Yol. 70.] THROUGH THE AXDES OF PERU .VXD BOLIVIA. 5 



of the country is covered by a great sheet of alluvium, forming 

 a flat unrelieved desert : this ends abruptly in the valley of 

 La Paz, a mighty gorge with almost vertical sides, carved out 

 of the alluvial plateau and separating it from the high peaks of the 

 Eastern Cordillera, which, rising to altitudes of over 21,000 feet, 

 bound it on the east. The view, from the barren plain or Alta- 

 planicie, of the fertile valley, with the city of La Paz 1600 feet or 

 more below, is one of unsurpassed beauty. 



From La Paz our traverse was continued eastwards up the 

 valley of Chuquiagillo, renowned for its rich gold-washings. The 

 road crosses the pass at Huacuyo (15,550 feet), descending 

 rapidly to Pongo [36 kiloms.] and the custom-house of Unduavi 

 (10,427 feet). From here, after rising over the spur of Sillutin- 

 cara (11,600 feet), a descent of nearly 5000 feet in 12 miles is 

 made to Bella Vista [Qo kiloms. ; 6890 feet]. From Sandillani 

 [69 kiloms.] the road once more descends rapidly down the winding 

 Tunca Queuta ( Aymara = ' ten turns ') to the River Chairo, which 

 unites, with the Elena and the Yoloza to form the Coroieo, 

 one of the chief tributaries of the Caca. Leaving the village of 

 Coroieo (6530 feet) on the right, and crossing the river, one 

 reaches the hacienda of Mururata a short distance farther on 

 [100 kiloms. ; 3390 feet]. This forms the eastern termination of 

 our first section. 



For a clearer understanding of the geological features of the 

 main section, it was found necessary to make a number of sub- 

 sidiary journe} r s in this part of the country, the most important 

 of which are described in the following paragraphs. 



That portion of the railway-section that lies between Huaylas 

 and Poconchile (see PI. X, fig. 2) was examined when returning to 

 the coast, since on our journey inland we proceeded from the latter 

 village up the branch-line to Molino, and thence continued up the 

 valley of the Llutah to Jamiraya, at the western end of the 

 gorge of that name ; finding it impossible to proceed farther, 

 owing to obliteration of the trail, we ascended the southern side 

 of the valley by the cuesta 1 of Cuescolla to the village of Putre, 

 which lies at the foot of Mount Taapaca (PI. I). 



E-ecrossing the Llutah near Patapatani, we once more reached 

 the railway-cuttings above Huaylas. On our return journey we 

 paid a second visit to the Jamiraya gorge, descending into it by 

 the cuesta of Socoroma at its deepest part above Jamiraya and 

 at Ancolocalla, a few miles up river. 



This gorge at Patapatani, its upper or eastern end (PL II), is 

 about 250 feet deep, with vertical sides ; from here it is continued 

 for a distance of some 10 miles to Jamiraya. attaining a maximum 

 depth of over 6000 feet. Its sides are so steep, being often little 

 short of vertical, that it is only possible to descend to the river at 

 one or two places. At one time, the idea was conceived of carrying 



1 Cuesta (Spanish = ' slope ') is here used to denote a mountain -spur up 

 which a steep trail is cut in a zig*zag manner. 



