20 BOOKS AND CUERENT LITERATURE 



solar-control model by which the areas of probable rainfall or dryness 

 for any, month of the year can be quickly shown. 



Although the memoir as a whole treats only of rainfall, two instruc- 

 tive chapters are devoted to the author's climograph and hythergraph 

 and are of much interest. The former has to do with the wet-bulb 

 thermometer and relative humidity readings. Climographs of repre- 

 sentative Australian stations in comparison with those for Berlin and 

 London are given. Hythergraphs are shown for certain tropical sta- 

 tions in Australia and a composite hythergraph is evolved which is used 

 as a comparison in an interesting figure giving those for various Indian 

 economic plants. 



An instructive vegetation map, based on the one by Diels, shows the 

 situation of the great groups and their relation to the 10-inch isohyet. 

 This map, together with the author's tabulated characterization of the 

 rainfall as regards the times of its probable occurrence, leads one to 

 suggest that very possibly the xerophytic stamp which so strongly 

 marks the Australian vegetation, may be due to the fact that it is 

 periodically exposed to drought. However that may be, it is shown 

 that the "mulga" (Acacia spp.) regions receive rains in summer 

 mainly, while the "mallee" (Eucalyptus spp.) are exposed to winter 

 rains. In the savannah and savannah woodlands, both of which 

 extend broadly latitudinally as well as longitudinally, the season of 

 rain depends on the situation, being mainly in summer or winter, as 

 the case may be. It is in restricted rain forests only that the rainfall is 

 fairly uniform throughout the year. So far as the actual amount of 

 precipitation in these various regions is concerned, it can be summed 

 up as follows: The rainfall of the mulga and desert regions is under 

 10 inches. That of the mallee is 10 to 20 inches as is also that of the 

 savannah. In the savannah woodland regions, however, it ranges 

 from 15 to 50 inches annually. And, finalty, in the rain forests the 

 precipitation amounts to over 30 inches a year. 



Omitting further account of the discussions relating to the general 

 climatic conditions, which are very interestingly treated, I will briefly 

 review the discussion of the regional correlations and rain origins, to 

 which the major portion of the memoir is devoted. 



The continent is conveniently divided into 15 regions and to each 

 region is given a separate chapter. Regional maps showing rainfall 

 and contours accompany formal presentation of the subject matter. 

 Storm charts and graphs are freely used. A striking feature is the 

 occasional employment of block models to illustrate possible topo- 



