26 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



found for the West India cyclones. The average velocity of progress of these storms when ad- 

 vancing northward was 9.3 miles per hour. 



The average course of these storms, after turning eastward, was 35° east of north, and their 

 velocity of progress was 9.8 miles, which is scarcely half of tlie velocity found for West India 

 cyclones. 



Column 10 shows that rain aecomi)anied every one of these storms, and generally the rain-fall 

 was escessivelj- great. These observations were gi nerally made from vessels on the ocean, and 

 the amount of the rainfall could not be measured, but the rain was generally characterized by the 

 strongest terms which the English language furnishes, such as, very heavy rain — constant heavy 

 rain — ceaseless rain— excessively heavy rain — incessant heavy rain — sheets of rain — deluge of rain — 

 rain poured down in torrents — dense, thick, impenetrable rain — rain with a vengeance — rain and 

 very large hail — rain and sleet — hard sleet — torrents of rain and sleet, &c. 



38. When a storm center passed overland where a rain-gauge was observed the measurements 

 showed that the preceding terms were no exaggeration. The following table shows the amount of 

 rainfall in twenty-four hours at certain stations within the limits of the cyclones named in 

 Table VII : ' 



Table VIII. — Eainfall in trojncal cyclones. 



From this table we see that these cyclones were accompanied by an amount of j-ain such as 

 seldom occurs even within the tropics, and we seem authorized to conclude that excessive rain 



