RAINFALL AND DISCHARGE OF THE MURRAY RIVER. XLIX. 
ground without rising. It is first caused to ascend by being 
intermixed with the vapour particles. According to their 
buoyancy, the vapour particles tend upwards through the atmos- 
phere, thereby carrying the air with which they are intermixed 
upwards also, and the ascent of a current of damp air is estab- 
lished. The vapour is the real cause of this motion, each and all 
of its particles acting as so many minute balloons. The ascending 
current after having passed through the heated surface air, gets 
suddenly into a much colder stratum, and condensation takes 
place by mixture of the rising damp air with cold air as it is 
passing through.” 
Coming in contact with the earth’s surface, a portion of 
the rainfall is immediately absorbed by vegetation, a portion 
runs directly into streams, a portion is evaporated, a portion 
sinks into rock fissures and reappears in springs. As in 
the case of the artesian area of New South Wales, a con- 
siderable proportion is absorbed in the porous strata, thereby 
constituting a supply of great importance to the State in 
an area sadly deficient in running streams. 
Summer Thunder-Storms in Australia.—With reference 
to the cause of rainfall, as stated in the foot-note below, a 
large percentage of the rain of Australia is precipitated in 
connection with storms of the last mentioned class. Inthe 
southern portion of Queensland, which forms the northern 
part of the drainage area of the Darling River, and in the 
Western Division of New South Wales, there are frequent 
visitations of cyclonic storms, often resulting in swelling 
the Darling, when the Murrumbidgee, Goulburn, and other 
rivers are diminishing in volume. 
Professor Henry, Chief of the United States Weather Bureau: 
Rainfall of the United States.—‘“ Cooling by expansion is one of 
the most effective causes of rainfall. The ascensional movement 
of air is brought about in several ways, chief of which are: (1) 
The air may be forced up the side of a mountain into a region of 
4—Sept 1906. 
