302 ANNUAL OF SCIENTIFIC DISCOVERY. 



vapor. This theory was illustrated by experiment, the radiation of heat 

 from aqueous vapor being proved by the galvanometer. Prof. Frank- 

 land, at some length, adduced his reasons for believing that this theory 

 took cognizance of the following points in the history of the glacial 

 epoch, 1. That its effects were felt over the entire globe. 2. That it 

 occurred at a geological period. 3. That it was preceded by a period of 

 indefinite duration, in which glacial action was entirely wanting, or very 

 insignificant. 4. That during its continuance, atmospheric precipitation 

 was much greater, and the hight of the snow-line considerably less than 

 at present. 5. That it was followed by a period up to the present 

 time when glacial action became again insignificant, the sole c tuse of 

 the phenomena of the glacial epoch being due to the oceans, then having 

 a higher temperature than now, and when the globe was cooling down, 

 the land cooling more rapidly than the sea. In conclusion, Prof. Frank- 

 land expressed his opinion that the moon had also passed through a gla- 

 cial epoch, and that the valleys, hills, and streaks of its surface (which 

 were shown in a magnified photograph by the electric lamp), were not 

 improbably due to glacial action ; adding, with reference to the apparent 

 desolate condition of the moon, that it is probable " that a liquid ocean 

 can only exist upon the surface of a planet so long as the latter retains a 

 high internal temperature ; that, therefore, the moon becomes a prophetic 

 picture of the ultimate fate awaiting our own earth, when, deprived of an 

 external ocean, and of all but an annual rotation upon its axis, it shall re- 

 volve around the sun, an arid, lifeless wilderness, one hemisphere ex- 

 posed to the perpetual glare of a cloudless sun, the other shrouded in 

 eternal night." 



THE INCREASING DESICCATION OF INNER SOUTHERN AFRICA. 



A paper on the above subject was read by Mr. J. F. Wilson, at the 

 last meeting of the British Association. A very noticeable fact has of 

 late years attracted the attention of residents in South Africa, namely, 

 the gradual drying up of large tracts of country in the Trans-Gariep 

 region. The Calabari Desert is gaining in extent, gradually swallowing 

 up large portions of habitable country on its borders. Springs of water 

 have diminished in their flow, and pools, such as that at Serotli, de- 

 scribed by Livingstone, are now either dry or rapidly becoming so. A 

 long list of springs and pools now gradually drying up was given by the 

 author of the paper. The great change, however, had commenced if we 

 may trust native traditions, long before the advent of Europeans, which 

 are eorrobor<ted by the existence of an immense number of stumps and 

 roots of acaciiB in tracts where now not a single living tree is to be seen. 

 In seeking to account for this, it was necessary to dismiss from the mind 

 all idea of cosmical changes or earthquakes, of which no trace is visible in 

 Southern Africa. The causes lie in the physical characteristics of the 

 country and in the customs of the inhabitants. The region drained by 

 the Orange River is naturally arid, from the interposition of the Quath- 

 lumbu Mountains between it and the Indian Ocean, whence the chief 

 Miii-clouds are derived. The prevailing winds are from the northeast. 

 The clouds heavily laden with vapor from the Indian Ocean, are driven 

 over Catt'raria, watering these lands luxuriously: but when the moisture- 

 be.iring nimbi arrive at the summits of the mountain range which divides 

 Calfrana from the interior country, they are not only deprived already 



