230 MEMORIES OF MY LIFE 



The only fairly well understood feature in those 

 times, of movements of the air, was that of the 

 cyclone, or the huge tropical whirlwind carrying 

 destruction with it. It had been observed that when 

 these whirlwinds occurred in the northern hemi- 

 sphere they circled in the opposite direction to that of 

 the hands of a clock, round a centre of low barometric 

 pressure, and therefore round an area of uprush of 

 heated and moist air, accompanied, as it would be, 

 with heavy rains. This circling was justly attributed 

 to the spherical shape of the earth in combination 

 with its easterly rotation. An indraught, coming 

 from the direction of the equator, was impressed with 

 an excess of easterly movement, and one from the 

 nearest pole with a deficiency ; in other words, the 

 latter had a westerly movement relatively to the 

 place of observation. The observed twist was the 

 necessary result of their coming together. An 

 opposite direction of twist occurred, as would have 

 been expected, in the two hemispheres ; in the 

 southern one, the whirlwind circled round the area 

 of uprush in the same direction as the hands of a 

 clock. It was also surmised, that the direction of the 

 wind in ordinary weather was everywhere governed 

 by the same twisting conditions as in the terrible 

 cyclones of the tropics, where it had first been noticed. 



I felt greatly disposed to examine more closely 

 into these movements of the air, and it occurred to 

 me that enough help for the purpose might be obtained 

 in Europe from existing observatories, light-houses, 

 and ships in the neighbouring seas. They would 

 enable an experimental map to be made thrice daily 

 for a month, in which the observations should be at 



