TRANSACTIONS OF SECTION E. 9o7 



safeguarded their vigour. Similarly, the Brazilian highlands largely confined them 

 to the great valley as they swept r.ortliward to do battle, in the heart of South 

 America, with the warm vapours generated from the Pampean Sea and ancient 

 lake, and the steaming, tropical basin of the Amazon. The extension of the vapour 

 belt southward towards the Atlantic Ocean carried the equatorial currents nearer to 

 the polar ones, thus inviting frequent atmospheric disturbance and resultant storm 

 action. As the hot vapour-laden winds, fertile in elements of force, met the 

 southern cold ones, a prodigious amount of heat was set free by condensation. Into 

 the vacuum thus created the opposing currents rushed with ever-increasing rivalry, 

 enlarging the area of mechanical action, condensation, and vacuum, and augmenting 

 the violence of the storm-waters, which, sweeping along the mountain slopes, must 

 liave rapidly disintegrated and eroded them, and have acted as a potent agent to 

 transport to their base much of the material from which the Pampean beds were 

 sifted. The rainfall over the inter- Andean region must have produced many large 

 lakes similar to Lake Titicaca, and a great river system, which, tributary to the 

 Colorado, swelled it into a stream of the first rank, pouring into it the sand and 

 silt which have completely filled the enormous estuary, the outline of which is still 

 traceable. 



One may believe that an increased rainfall gave a luxuriant vegetation, where 

 herds of gigantic mammalia found feeding ground; from which, from time to time, 

 they were swept, by storm or swollen river, into the Pampean Sea, where also they 

 may have lost their lives in other ways, their remains being distributed over it by 

 the currents. 



To a minor degree the ancient sea and lake must have affected the inter- Andean 

 climate, from Cuzco to the south, throughout the lacustrine basin of Titicaca, 

 giving it greater rainfall and fertility than it now has. Geological examinations 

 show that Titicaca was once one of the large lakes of the world, and that it has 

 slowly been drying up. Does its gradual diminution date from the disappearance 

 of the Pampean Sea and Mojos Lake ? 



Savage man may have lived in South America on the mountain slopes round 

 the ancient sea. If so, he possibly hunted the mastodon, the megatherium, and 

 numerous other of the gigantic fauna which probably were co-existent with him. 

 His only highway, between the eastern and western halves of the continent, must 

 have crossed the elevated region at the head of the Pampean Sea, lying between 

 17° and 19° south latitude, which is still the only route in use for communication 

 bv land between Bolivia and Matto Grosso. 



The following Papers and Report were read: — 



L On Waves.^ By Vaughan Cornish, M.Sc, F.R.G.S., F.C.S. 



The author is engaged upon an investigation of the phenomena of waves as 

 far as they come within the scope of physical geography, and he exhibited to 

 the Section a series of lantern slides illustrating various branches of the subject, 

 including ocean waves, breakers, the tidal bore, ship waves, waves of rivers, the 

 rippling of sand by wind, sand dunes, ripple mark and ripple drift, wave clouds, 

 and rock waves. 



2. Report on the Climate of Tropical Africa. 

 See Reports, p. 603. 



3. The Temperature and Salinity of the Surface Waters of the North 

 Atlantic during the years 1895-96. By H. N. Dickson, F.R.S.E. 



The author described the first results of a discussion of observations of surface 

 temperature made in the North Atlantic during the two complete years 1895 and 



' The Paper will be published in the Gcojraphieal Journal. 



