go2 Marvels of the Universe 
The pressure at the centre of a 
cyclone is always lower than at 
its borders. When this fall is 
gradual we have the more or 
less unsettled weather condi- 
tions with which we are all 
familiar ; when it is very rapid 
over a short space we get 
the storms of greater or less 
violence to which various local 
names are also given. The 
tropical cyclones, besides being 
more intense, are usually much 
smaller than those of tem- 
perate regions. Of a some- 
what different character is the 
tornado, which may be described 
as a mass of air in rapid rota- 
tion round a nearly vertical 
axis; in height it may be as 
much as one hundred and fifty 
to two hundred feet, but its 
breadth is usually very much 
less. The cylinder of air, or 
funnel “ spout,” as it is called, 
has a violent upward motion ; 
it sways to and fro, and the 
whole system also has a for- 
ward motion. The speed of 
the rotary motion may some- 
times run up to five hundred 
miles per hour; the upward 
A CYCLONE IN AUSTRALIA. motion, though slower, often 
When these cyclones, or * willi-willis,’’ take place the damage caused is exceeds eighty miles per hour. 
enormous. Ships are often thrown inland by huge tidal waves, while in the swirl of The forward movement is much 
the ebb thousands of cattle perish. 
slower than this, and usually 
in a north-easterly direction. The central column of rarefied air being cooled by expansion, any 
vapour within it is condensed, and so we sometimes have a “ water-spout”’ accompanying it. Great 
damage is often done by tornadoes—houses, trees, fences, churches, etc., being blown down and 
[By Arthur Tuwidle. 
carried up into the air for a considerable distance. 
The “ dust-whirl’”’ of the roadside is a miniature tornado, whilst the “simoon”’ of the desert 
is a whirlwind carrying large masses of sand and dust, under which caravans are sometimes buried. 
The “ pampero”’ of the Argentines is accompanied by much moisture, whence arises thunder, rain, 
and a typical form of cloud, the “ cloud wreath.” In northern latitudes a similar kind of disturbance 
is known as a line squall, and such a line squall it was which caused the capsizing of H.M.S. Eurydice 
off the Isle of Wight in 1878. 
Of various other local varieties of Wind distinguished by special names, we may mention the 
Féhn Wind of Switzerland, the Sirocco of Italy, the Mistral of Southern France, the Chinook 
Wind of Canada, the Blizzards and “ Barbers’ of the States, the Nortes of Mexico, the Harmattan 
