G4 On the Temperature and Atmosphere of Barbadoes, 



In December and January, only fourteen direct determinations were ob- 

 tained at 3 p. M. These being treated in the same manner, give the cal- 

 culated dew point 66°.13, and the observed 6&°.56,— the former being 

 In excess by 0°.27. These experiments made, respectively, when the 

 moisture and stillness of the atmosphere were greatest, and when they 

 were about least, will give a pretty accurate idea of how far the indica- 

 tions of the wet bulb thermometer may be depended on in the West 

 Indies. 



A similar depression occurs in the dew point at 3 p. m., in most of the 

 months, to that already noticed in the temperature of the air about mid- 

 day, and which was obviously attributable to the same cause. The 

 variations of the dew point from day to day, though sufRcientl}" marked, 

 were never very great; it was always higher with a south-easterly wind 

 than with the regular trade, unless immediately after rain; and when 

 the moon's declination was north, the air being then generally' stiller 

 than when it was to the south of the equator, the dew point was usually 

 considerably above the average for the corresponding month. 



The cloudiness of the s\y varied considerably in different months, and 

 scarcely less so at various periods of the same month ; its effect on the 

 temperature, as was to be expected, and, indeed, as is obvious from the 

 table, was very considerable. From the impossibility of procuring an 

 eligible site for a rain-gauge, which, at the same time, might be free 

 from interruption, I was unable to form any idea of the quantity that 

 fell. The number of days on which it occurred are given in table II. ; 

 and, though the year was accounted unusually dry, it is found that 

 showers, frequently heavy, fell, on the average, every second da}'. 

 Heavy and continuous rain always came from the southward of east j 

 but up to October, when the moon's declination was northerly, yevy 

 heavy showers from the E.N.E. or NE. were common. 



The prevailing winds are given in the table, in the order of their pre- 

 valence, during each month. The regular trade wund from the E.N.E. 

 predominates ; and the others, v/ith very few exceptions, are but va- 

 rieties of it. The generally received explanation of the cause of the 

 trade winds is accurate in the main; but there are several most im- 

 portant modifications, which seem to be chiefly owing to the differences 

 in the moon's declination and time of transit, and which, if fairly exa- 

 mined into, bid fair to throw much light on the origin of, if not actually 

 to account for, the phenomena of the West Indian hurricane. 



