Til AHA BOSIGO SAND DUNES. 51 



illustrates on a small scale what takes place on the dump, or 

 dune, on a large scale. 



if Fig. 3 represents a cross section of a ripple with the wind 

 in the direction indicated by the arrow, the particles of sand 

 lying on the surface ab are rolled or lifted along by the wind 

 and over the summit down the slope be, so that the section of 

 the ripple becomes a'b'c' , then a"b"c," and so on. 



Fig. 3. 



Thus the occurrence and varying size, position and form of 

 the sand-dunes appears to be quite simply accounted for, and 

 the dunes furnish ocular evidence of the part played by wind in 

 altering the contour of the earth's surface. 



TRANSACTIONS OF SOCIETIES. 



Royal Society of South Africa. — Wednesday, June 19th: Dr. L/ 

 Peringuey, F.E.S., F.Z.S., President, in the chair. — " The rainfall on Table 

 Mountain for thirty years": T. Stewart. Rainfall observation on Table 

 Mountain was begun in January, 1881, with two stations, one at Disa Head 

 and one at YVaai Kopje. In 1S84, two more, at Kasteel Poort and St. 

 Michael's were added. In 1892 seven additional stations were selected. The 

 average yearly rainfall during 2J years was as follows: 61.74 inches at Kas- 

 teel Poort, 2,483 feet above sea-level ; 75.24 inches at St. Michael's, 3,050 feet 

 above sea-level; and 67.63 inches at Waai Kopje, 3. too feet above sea-level. 

 The summit of the mountain (Maclear's Beacon) is its wettest place; 

 the rainfall at the gauge there gave 73.34 inches during the driest year 

 (1896), and 126.18 inches during the wettest year (1902). — "On tidal phe- 

 nomena in wells near Cradock " : Prof. A. Young. The depth of the 

 deepest well is 225 feet. Thermal waters, containing sulphuretted hydrogen 

 issue, accompanied by large quantities of methane. Measurements of the 

 pressure at which the water issues show a fluctuation analogous to the 

 tidal fluctuations of the sea. Components having the following wave 

 periods were isolated: ( 1 ) 12 hrs. 25 mins., (2) i_> his. mins.. (3) 2T, hrs. 

 57 mins.. (4) an unharmonic residuum, which proved to be the vertical 

 inversion of the barograph curve. The author concludes, therefore, that 

 these fluctuations are to be attributed, directly or indirectly, to astronomical 

 causes. The wells are more than 100 miles from the coast, and over 2,700 

 feet above sea-level. 



Wednesday. July 17th: Dr. L. Peringuey, F.E.S., F.Z.S., President, 

 in the chair. — " Addendum to revised list of the flora of Natal " : J. M. 

 "Wood. — " Descriptions of some new batrachia and lacertilia from South 

 Africa": J. Hewitt and P. A. Methuen. The following were described: 

 Natalobatrachus bonebcrgi, new genus and species ; Bufo 

 benhoidetx, new species; Tetradactylus eastwoodcr, new species; and 

 Zonurus Cceruleopunctatus, new species. — " Notes on Namaqualand Bush- 

 men " : Miss L. Currle. An account of the characteristics of Cape Colony 

 Bushmen, including descriptions of their mode of life, their food, their 



