1 Jay., 1899.] QUEENSLAND AGRICULTURAL JOURNAL. 67 
moisturein the air. This can be hastened by the use of afan. Very much the same 
thing occurs in vegetable life. Living vegetation possessesa normal temperature 
of 45 degrees I". to 50 degrees F. When the weather is very hot the spiracles 
or pores open, and there is considerable transpiration of moisture. Exact 
observations by American scientists have shown that a moderate-sized soft- 
leaved tree will transpire as much as 40 gallons of water perday. It is easy to 
imagine that a very large quantity of water must be thrown out upon the air 
when we remember that trees renew their leaves and make a deal of growth 
every year. Deciduous trees throw their leaves within a week or two ; evergreen 
trees are shedding and renewing all the year round. Nearly all, if not all, 
this growth is made by the sap brought up from the roots. This sap contains 
a very small portion of solids, but only those solids are used in the coustruction - 
of leaves, twigs, wood, bark, &c. All the rest, consisting of water, is transpired, 
and goes into the air. What an amount of moisture there must be thrown 
into the atmosphere where large areas of forest exist! In the course of 
transpiration and absorption a cooling effect is naturally produced. What 
would be the effect of the presence of a large bulk of living vegetation having 
a normal temperature of, say, 50 degrees I. when the air temperature is at 100 
degrees F’. or even 150 degrees F'.? It is well known that hot air is always 
moist air, and that air will absorb moisture according to its temperature. 
When it is cooled down, it parts with an equivalent portion of its moisture ; 
so, when a hot wind comes into contact with a mass of cool green vegetation, 
it must be cooled, and it must part with some portion of its moisture. Where 
tall trees exist, there is shade, and shade is cooler than the open sunshine— 
every animal knows this—and even the shade of a rock is cool. The shade 
under tall green trees is much cooler than under rocks or walls. During very 
hot weather the difference between the heat in the open and beneath the shade 
of green trees is very considerable. Beneath the shade of forests a rich humus 
is formed, and this keeps the roots cool in summer and warm in winter, besides 
absorbing and retaining a great quantity of water. By this means the springs 
are kept supplied, and rivulets are maintained. When the trees are destroyed 
the humus is quickly burned up by the heat of the sun, and instead of the 
rains and dews being retained all the water rushes at once into the channels 
and away to the sea. The soil is impoverished greatly, and plants perish for 
want of moisture. Everyone knows that dark substances absorb heat, and 
light dry substances radiate or throw off heat. Where large forests exist, the 
leaves absorb and reduce heat. Where large areas of open country 
prevail — especially where dry grass, bare soil, and white vegetation 
only grows — there is a great radiation of heat, a tremendous 
expansion of the air above, and therefore there is a very large area 
of “high pressure” to be pushed out of the way when a “low pressure ”’ 
area approaches our coast. If it were possible to establish a thousand square 
miles of forest in the Far North, it would most probably have a most bene- 
ficial influence on the climate to the southward, because there would be an 
area of much lower pressure over the forest ‘That South Australia once 
ossessed large forests and a great rainfall is evident from the great deposits of 
ones of monstrous kangaroos, wombats, marsupial lions, and moa birds so far 
north as Lake Callabonna or Lake Mulligan. These monstrous animals could 
not have existed without a most luxuriant vegetation, and no doubt exists that 
these conditions prevailed long since the glacial period, which also once pre- 
yailed. What brought about the destruction of the heavy forests and 
cessation of the tropical rains, no one at present can explain. It may have been 
due to an inroad of girdling insects, or to a rather long period of dry weather 
and occurrence of disastrous fires, but that there was once luxuriant vegetation 
is quite as certain as its absence now. It would be as wrong in himself to 
dogmatise upon the matter as it is wrong in others to do so in a contrary 
direction. It did not follow because a man was scientific in regard to geology, 
entomology, or any other “ ology” that he should be able to decide positively 
that “trees do not exercise any influence upon climate, rainfall, temperature, 
