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139 
Cyclones, 
(Wir SONr (PLATE: ) 
By Appian J. Brown, F.I.C., F.C.S. 
(Read before the Society, February ist, 1889.) 
of Galileo, the great astronomer, took a glass tube, 
closed at one end but open at the other, and filled it 
with quicksilver. After putting his finger firmly on 
the open end of the tube to prevent the escape of the metal, he 
turned that end downwards and plunged it underneath the surface 
of quicksilver in another vessel. In this position, of course no air 
could possibly get into the tube. On removing his finger from the 
end of the tube, the quicksilver at once sank a certain distance, 
and then remained steady, leaving a column of the metal about 30 
inches in height standing in the tube. I will now repeat this ex- 
periment. At first sight this experiment looks curious, for why 
does not the whole of this heavy metal run out of the tube? 
Part of it has gone, as we see; why does not the rest follow? 
Torricelli accounted for the phenomenon by saying that the air, 
which, like everything else in this world, possesses weight, pressed 
so heavily on the quicksilver outside the tube, that it only allowed 
the metal to escape until the column of quicksilver inside the 
tube sank to such a point that the weight of it, pressing down- 
wards, was exactly equal to the weight of the air pressing on the 
quicksilver outside, and that in this way they balanced each 
le N the year 1643, an Italian named Torricelli, a pupil 
‘other. This theory of Torricelli’s was eventually proved to be 
quite true by Pascal, a Frenchman. Pascal argued in this 
_ manner: he said, if the weight of the column of air above us 
really supports the column of quicksilver in this tube, then, if I 
carry the tube up the side of a mountain, the higher I go the less 
