4 ME. J. A. DOUGLAS ON GEOLOGICAL SECTIONS [vol. lxxvi,. 



II. Main Topographical Featukes of the Country included 

 in the Second Section (Mollendo to the Inampaki 

 Eivee). 



From the port of Mollendo, the southern railway of Peru follows 

 the coast towards the south-east as far as the hamlet of Mejia 

 (kilometre 15). Thence turning inland it ascends to the station of 

 Tambo (kil. 30, alt. 1000 feet), situated on a flat plain at a con- 

 siderable height above the village of that name which lies in a 

 fertile valley on the south. 



This coastal region, as it may be termed, is particularly well 

 defined when viewed from a passing steamer. It has been 

 described by Prof. Isaiah Bowman as being composed of gently 

 sloping rock-benches of huge size, formed by the sea, and subse- 

 quently uplifted to a height of at least 1500 feet. Along the 

 inner margin of these terraces coves are to be found, like those 

 now seen at rnany places on the present strand-line, or but little 

 above it. 



The same author further cites the discovery, at an elevation of 

 800 feet, of a clay-bank containing recent shells of the same sort 

 as those now found on the beach, and from this concludes that 



' after the formation of the terrace at this level and its partial dissection 

 as the result of elevation, it was again submerged long enough and deep 

 enough for the formation of the clay and deposition of the shells ; a second 

 uplift then brought the whole above water, and it is this movement that is 

 continuing to-day.' 



That a comparatively recent uplift has taken place is manifest 

 from the abundant remains of raised beach preserved along the foot 

 of this shelving plateau, consisting chiefly of angular fragments of 

 gneiss and granite derived in situ from the rocks cropping out along 

 the shore. These remains, however, so far as my own observations 

 go, do not extend more than about 50 feet above present high-water 

 mark, and the assumption that the uplift has amounted to as much 

 as 800 feet in recent times and is still continuing at the present 

 day, as held by Prof. Bowman, is, I think, hard to reconcile with 

 facts recorded from other parts of the coast. 



I have already shown that the presence of pre-Spanish burial 

 tumuli only a few feet above high-water mark at Arica precludes 

 the possibility of any considerable rise in the last 400 years ; a 

 change of level of 4 feet, in fact, might with reason be taken to be 

 the absolute maximum, or such loosely-consolidated mounds must 

 inevitably have been destroj^ed by wave-action. A rise of 800 feet, 

 if the elevation be considered as having taken place at a uniform 

 rate, would therefore necessitate a period of some 80,000 years. 



I have previously suggested that a considerable post-Pleistocene 

 elevation must be assumed, in order to account for the fossil 

 mammalian fauna of the inter- Andean region ; and some authors 

 have gone so far as to claim a rise of over 1000 feet in the last 

 11,000 years, in order to explain the position of the ruined city of 

 Tiahuanacu in its present barren site. Effects due to climatal 



