22 BOOKS AND CURRENT LITERATURE 



which extends north-west and south-east across the north-east portion 

 of the region. Oodnadatta, with a rainfall of 4.68 inches is situated 

 along this line. The area with less than 5 inches of rainfall is over 

 36,000 square miles. The rain in the extreme north of the Eyre region 

 is due to northern, tropical, influences. Oodnadatta, however, which is 

 somewhat south of the northern boundary of the state, receives rain in 

 winter as well. But those of the south-west in particular are in winter 

 only. 



In presenting an account of the character of the rainfall, which is 

 summarized in an instructive table, it is found that 64 per cent is of 

 the trough type, 20 per cent antarctic, 10 per cent tropic, and 6 per cent 

 non-isobaric. In other words, one-fifth of the rainfall is that of winter, 

 one-tenth is that of summer, and far the most occurs from a union of 

 lows originating in the south and north, and do not appear so strictly 

 seasonal as the other two. The north-south swing of the climatic 

 complex is 1200 miles, or more. Since the northernmost point attained 

 by the center of highs coincides fairly well with the north boundary of 

 the state, the southern extremity reached is far south of the Eyre 

 region, or indeed of South Australia. The effect of this seasonal swing 

 is graphically shown by the author for the whole of Australia, as men- 

 tioned above, in his solar-control model. The influence of the swing on 

 the rainfall of the Eyre region can be easily and strikingly shown by 

 inserting the outlines of the region on the model. The types of winter 

 and summer storms are various, and need not be detailed here. They 

 are illustrated by numerous charts and fully described 



The general treatment of the rainfall as an environing factor of the 

 plants has been from the standpoint of a meteorologist, one would 

 judge from reading the work, rather than from that of a botanist, and 

 possibly this would ensure its better handling! Certainly the work is 

 well done. One cannot help questioning, however, the values of storms 

 of the same amount, or, which is not the same thing, rainfalls equal in 

 amount. It is clear that a 5-inch rainfall which is mostly in summer, 

 for example, may be less effective than a rainfall similar in amount but 

 occurring mainly in winter. This is largely owing to the unequal 

 rates of evaporation in the two seasons, and its corresponding effect on 

 plants. Then, also, it seems possible that storms at any season which 

 measure 0.15 inch or less, are of little use to plants, although a suc- 

 cession of them a few days apart would make a fair showing on the 

 rainfall totals. That this may be of no little importance is suggested 

 by the fact that at Oodnadatta in 1906, for example, 56 per cent of the 



