1874.] Tropical Zoology. 331 
out victorious from the struggle for existence. Were it not 
for man’s constant intervention, the vine and the wheat, the 
rose and the carnation, would soon succumb to a tribe of 
weeds as devoid of utility as of beauty. Further, when man 
takes in hand to improve any race, his first step is to stamp 
out the struggle for existence, whether between individuals 
of such race or between the race itself and other species. 
If we examine the case of a turnip-field we find that the 
number of plants is strictly proportioned to the extent of the 
land, and that an unrelenting war is waged against all 
weeds. Were the struggle for existence permitted to rage 
unchecked we should certainly find some of the turnips 
larger than others, whether in virtue of more favourable 
circumstances or of more intense vitality in the seed. But 
the yield from the whole plot would be trifling, and no rout 
would reach the dimensions attained where every plant finds 
a sufficiency of room and of nutriment. Perhaps, in like 
manner, the men most valuable to the world—the discoverers 
and inventors—are not those who win the ordinary prizes of 
life. Perhaps society or its rulers may one day find it 
necessary to take for a model the farmer’s management of 
his turnip-field. 
We can do no more than briefly call attention to the 
author’s view of cyclones. From these terrific manifestations 
of force down to the eddy of dust which we often see crossing 
aroad ora common, we have, according to Mr. Belt, one 
and the same phenomenon, differing merely in degree. 
Hence he recommends a careful study of these small dust- 
whirlwinds, as calculated to throw light upon the origin of 
cyclones. His own theory, first advanced in 1857, in a paper 
read before the Philosophical Institute of Victoria, is that 
the particles of air next the surface do not always rise im- 
mediately they are heated, but that they often remain and 
form a stratum of rarefied air next the surface, which is in 
a state of unstable equilibrium. ‘This continues until the 
heated strata are able, at some point where the ground 
favours a greater accumulation of heat, to break through 
the overlying strata of air and force their way upward. An 
Opening once made, the whole of the heated air moves 
toward it, and is drained off, the heavier layers sinking 
down and pressing it out. That hot air does not always 
immediately rise is proved by the hot winds of Australia, 
which blow from the heated interior towards the cooler 
south, instead of rising directly upwards. 
In conclusion, we feel bound to give this book our most 
cordial recommendation. Few men possessing any degree 
