Mabcu 1. 1901.1 



KNOWLEDGE. 



00 



country. The following tiguies are taken from a pajxn- 

 wliicb appearetl in the " QuaiUnly Joiu'iial of the Royal 

 Meteorological Society, and are based on the published 

 reports of the Cape Town Meteorologieal Commission. 



For the present purpose it will be couvonieut to 

 divide the Cape Peninsula into three ai-eas, nanioly, the 

 Western Division, the East-ern Division, and Natal. The 

 stations to wliich refex'ence will be made cover an arc<i 

 which extends from Cape Town to Durban, and reaches 

 as fai- north as Kimberley ; and they are, moreover, 

 at various heights above the sea level, and represent 

 climates of places which like Sinions Town is only "JO ft. in 

 height, and others like Aliwal North which has an 

 altitude of 4400 ft. Now tliere is a very wide range in the 

 yearly rainfall in these vaiious localities, and as regai'ds 

 the yeai'ly averages the records show that the values 

 range from 54.17 ins. at Bishop's Court, in the Western 

 Division, to 8.36 ins. at Camfer's Kraal in the Eastern 

 Division. Taking individual years, as much as 82.82 ins. 

 has fallen during twelve mouths at Durban, but. on the 

 other hand, at Camfer's Kraal the rain-gauge dm-ing a 

 certain year only succeeded in collecting rain to the 

 amount of 3.10 ins. The most obvious fact, therefore, 

 as regards the rainfall in South Africa, is its lack of 

 uniformity, and not onlv do the amounts vary from one 

 locality to another but there is also a lack of symmetrv 

 from year to year. In respect of the individu.il districts 

 tlie average yearly fall over the Western area is 

 27.34 ins.; over the Eastern, 17.06 ins.; and in Natal, 

 38.21 ins., the average for all stations combined being 

 22.44 ins. . Along mountain ranges such as Table 

 Mountain in the Cape Peninsula, and along the Katberg 

 and Amatola Mountains, the yearly fall varies from 50 

 to 70 ins. In parts covered with forests, as in T'Zt^nkania 

 on the south coast, and in Natal, the range is from 

 30 to 50 ins. A strip of country along the mountains 

 near and parallel to the coast in the eastern division of 

 Cape Colony has an average yearly fall of from 20 to 

 30 ins. ; and a band of country along the inland side of 

 Molepolola in Bechuaualand has from 10 to 20 ins. ; 

 while in a patch of country in the Great Karro lying 

 between Zwarteberg and the Nieuwvolt Mountains and 

 the extreme north-west regions of Cape Colony, the 

 average yearly fall is under 5 ins. 



The thi-ee districts mentionetl above are, of course, 

 drained by the Orange and Vaal rivei-s, and it has been 

 cajculated that they discharge into the oceaji 

 900,000.000.000 cubic feet of water during the year. 

 In the future administration of the countrj', therefore, 

 not the least of the important problems to be solved 

 will be those connected with devising some scheme 

 whereby this abundant supply of water may be stored 

 by sviitable reservoirs and irrigation works, and thus 

 rendered available for developing the agricultural 

 resources of the countiy. From this point of view, 

 those who concern themselves with collecting rainfall 

 statistics may be encouraged to continue their labours, 

 for in the work connected with the opening up of new 

 countries such statistics are of the highest value. 



As a means of fiu-ther illustrating the variation to 

 be observed in tlie amount of rain which falls in different 

 parts of South Africa, a table is appended which shows 

 for a few selected stations the mean yearly rainfall to- 

 gether with the total rainfall measured during the 

 wettest and the driest years experienced during the 

 period in which the obsei-vations were made, a period 

 which is in no case less than ten years. The height of each 

 station above the level of the sea is given in brackets. 



THE SIZE OF OCEAN WAVES.-Il. 



By V.vu<!HAN Cornish, M.s(j,(vic'r. ), f.c.s., k.r.g.s., 

 Afiionate of the Oiveng College. 



Paris .states that wind can create waves which move 

 faster than itself, but adds that when the sea is rough 

 the waves are always slower than the wind. He 

 endeavovu-s to find a relation between the velocity of 

 wind and that of waves, but when he has eliminated all 

 " swells," all ohservations in rather shallow water, and 

 all cases where there appeared to be circumstances 

 interfering with the required conditions, there remain 

 only 31 days' obsei-vation on which to found a generalisa^ 

 tion. The observations on these days give the velocity 

 of the wave proportional to the square root of the 

 velocity of the wind. He explicitly states, however, 

 that the number of observations is too few for the 

 establishment of an empirical law, and wishes for the 

 accumulation of a large mass of data, which, if carefully 

 discussed, might .show whether the above relationship 

 is merely accidental, or if, on the other hand, it is 

 general. 



More interesting, perhaps, are the two tables (II. 

 and III.), in which are grouped on two different plans 



Tahle II. 



the observations of the whole 4000 waves. In Table 

 II. the grouping is without regard to locality, being 



