128 GEOLOGY AND MINERALOGY OF XATAL. 



the surface soil in the hollows, assisted hy surface waters, sinks^ 

 down into the subsoil. In this way the difference in height between 

 the ridges and bottoms of the hollows is continually taking place. 



This process continues till there is no further soil within the hollows 

 and all has been extracted by the worms. These colonies of worms 

 in extending their fields of operations seem to keep to tho^e parts 

 where the soil is deepest and thus, instead of crossing the hollows, 

 they continue along their length until they unite with the adjacent 

 colony. Were it not for the clayey nature of the soil the castings 

 would be blown or washed away l)y the winds and rains, and the 

 level of the soil raised in some places and lowered in others. Thus 

 it is that again we have an instance of one of the smallest and 

 humblest of Nature's animals creating wonderful changes in the 

 Earth's surface. 



FORMATION OF DEW AT KIMBERLEY.— Dr. J.. 



K. Sutton, of Kimberley. has recently communicated to the 

 Royal Dublin Society some results of his local observations 

 regarding the deposition of dew. Those observations contradict 

 the common text-book statement that a clear sky is essential 

 to the formation of dew. That such a condition will usually 

 hasten the commencement of condensation is admitted, but the 

 deposition may, in the long run. be as abundant with clouds 

 as without them. With an atmosphere near the point of saturation, 

 there is little difference in the radiation of heat from the earth's 

 surface, whether the sky be clear or cloudy. The author, there- 

 fore, concludes that dampness of the air and length of the night 

 are the determining factors in the formation of dew rather than 

 clearness of the sky. 



THE VEGETATION OF SOUTH-WEST AFRICA. — 



In his paper before the Linnean Society on the 4th November, 

 Prof. H. H. W. Pearson stated that the floras of Bushmanland, 

 Namaqualand, Damaraland. and South Angola exhibit a distinct 

 relationship amongst themselves with the exception of the vegetation 

 found oii the Huilla Plateau in South Angola. Such differences 

 as there are may be accounted for mainly by differences of (i) 

 elevation, (2) atmospheric humidity, (3) depth of the permanently 

 available supplies of underground water, and (4) geographical 

 position. The rainfall, throughout the districts named, is sparse 

 and irregular, and the winter is a time of prolonged drought. 

 The floras exhibit an affinity with those of the South Central 

 African Highlands. Many of the s})ecies of South Angola are 

 derived from the coastal and Montane regions of West Tro})ical 

 Africa. The vegetation is xerophytic throughout, and marked 

 either by a short period of duration, or by the structural peculiarities 

 of dry climate perennials. Hairiness is not conspicuous ; suc- 

 culence, except in Lower Namaqualand. is not common : the 

 leaves are small and simple, with strongly developed cuticle ; 

 the root-system dee|i. 



