126 E. T. Quayle: 



moving air compelled to rise at least 3000 feet to cross the Aus- 

 tralian Alps, it can be shown that up till nearly the end of Octo- 

 ber, every addition to the water vapour means so much extra 

 condensation on the mountains. 



The monthly mean 9 a.m. relative humidities at Echuca from 

 March to October are 55, 63, 78, 86, 85, 78, 70 and 55 per cent. 

 (A minimum of 43 per cent, is reached in January). The cor- 

 responding 9 a.m. mean temperatures are 67°, 59°, 51°; 46°, 

 40°, 49°, 54°, and 62°, which are also very nearly the daily mean 

 temperatures. 



Now, since wind directions north of the Divide during these 

 months are very largely from points in the northern semicircle, 

 and almost entirely so in rainy weather, the air from the plains 

 is eventually driven over the mountains froming " the Divide." 

 This involves ascent of at least 2000 feet, and with westerly com- 

 ponents of wind direction from 3000 to 4000 feet, owing to the 

 altitude of that portion known as the Australian Alps. The 

 ascent being forced, the rate of cooling up to condensation level 

 will be adiabatic. The figures for March give the ascent neces- 

 sary for condensation as 3060 feet, for April 2340 feet, May 

 1200 feet, June 720 feet, July 720 feet, August 1190 feet, Sep- 

 tember 1730 feet, October 3000 feet. Hence, we can say that 

 •during the winter half of the year, at all events, practically every 

 addition to the moisture in the air over the plains, shows as cloud 

 before crossing the highlands. The consequent lowering of the 

 "level at which condensation takes place would certainly, in all 

 weathers, increase the effectiveness of fogs in wetting mountain 

 vegetation, and in rainy weather would increase the rainfall 

 probably to an extent greater than the actual addition. That the 

 former is not negligible is well shown by Dr. Marloth's experi- 

 ments on the moisture collecting power of vegetation in saturated 

 .air on Table Mountain. 



Other Evidences op Increased Rainfall from Local 

 Evaporation Areas. 



(1) From River Floods. 



Hints of evaporation effects increasing rainfall may be ob- 

 tained from a study of the average annual rainfall maps of 

 Northern Victoria and the Riverina, which show a marked ten- 

 dency for the isohyets to form loops or peaks extending down 

 the Murray and its numerous anabranches. 



