486 e QUEENSLAND AGRICULTURAL JOURNAL. [1 Junx, 1899. 
surrounding air. This expands, rises, and absorbs, without condensing them, 
the vapours brought by the sea winds. Rain only comes in sucha district when 
a contrary wind meets this hot current, packs its layers one on another, and, as 
it were, squeezes out the wet from them. Hence such rain, due to “ atmospheric 
perturbation,” generally comes floods, and zo¢ like the gentle natural rainfall of 
forest land. Storms are rare in timbered countries, the electricity of the air 
being gradually drawn off instead of accumulating. Hail especially is more 
rare in places which are well timbered than in those where trees are few. Hail 
is caused by the very rapid evaporation of rain passing through an exceedingly 
dry stratum of air. Evaporation, we know, always causes cold (this is the 
principle of water-coolers, &c), and in this case the latent heat of the rain is 
withdrawn so rapidly that the result is frozen raindrops. Hence, in timbered 
districts, where the rain is always moist, the evaporation is slower, and rain falls 
instead of hail. M. Cantégoil, Inspector of Forests at Carcassonne, in France, 
has made some important observations concerning the effect of hailstorms on 
forests. In France many of these storms are very destructive to property. He 
found that they generally made a leap over a forest. Take, for instance, a 
hailstorm which swept over the department of Ariége early in June, 1874, and 
entered that of Aude. As soon as it reached the forest lands the hail totally 
ceased, but when it reached the treeless department of the Eastern Pyrenees it 
began again with great fury, yet there was electricity enough in the air over the 
forests, for several fir-trees were struck and shivered to pieces. 
Those who in this colony live in the neighbourhood of forests or well- 
timbered lands, will notice that just after nightfall the air has a soft warmth, 
quite different from the cold chill that comes on after a hot dry day in the open 
plains and -bare untimbered districts. The reason is this—evaporation and 
radiation of heat are five times greater in treeless districts than in timbered 
ones. Perhaps some reader will say, and I fancy there must be a good many of 
this class in Queensland as elsewhere, if the trees bring more rain, they use up 
more than the treeless ground, for their roots drain the soil, and their leaves 
drain the atmosphere. This is not so, for though wood is more than half water, 
the amount of water contained in all the timber in a forest is the veriest trifle 
compared with the rain that falls on it during the year. Experiments show 
that the amount of water decomposed by an acre of forest is very much less 
than that required by an acre of cabbages, or clover, or wheat. Again, people 
argue that because pines and other trees dry up marshes, the number of trees 
in a place must lessen the water supply. This, again, is not so. . Experiments 
prove that this drying up is not due to evaporation through the leaves, or to 
the water being in any other way sucked up by the trees. All the trees that 
have this property can, and do, grow and thrive also in dry hungry soils. What 
they really do is this: They drain the soil, by virtue of their spreading roots, 
which enable the water to 1un off into the lower strata. 
From what I have already said, it may be seen that forests lower the 
temperature, while they prevent extremes, and increase the rainfall, at the same 
time that they regulate it and keep off those deluges of rain which cause sudden 
and destructive floods. Floods do occur in well-timbered districts; but they 
are not floods like those in bare treeless districts, which fill the rivers to over- 
flowing, and either scatter a mass of sand and shingle over the flooded landg 
and ruin it, or wash off all the best of the soil. From careful observations 
made in Savoy and Auvergne in France, it was found that wherever there were 
woods, or even quite recent plantations of trees, made terrace-wise along the 
hill sides, so as to cut across the torrents, and force them into a zigzag, the 
rains did little harm; but where the mountain and hill sides were bare, the 
roads and bridges were swept away in all directions, and the fertile lands in the 
yalleys were covered with sand and shingle. The peasantry soon saw the force 
of this, and began tree planting with most beneficial results. By tree planting 
they were able to save Embrun, at the mouth of the valley of Sainte Marthe, in 
the High Alps. This stream, after rains, is a raging torrent, and annually 
brought down millions of tons of rocks and sand, depositing them on the fertile 
