268 Meteorological Observations. 



The inequalities of pressure in the opposite seasons at Canton 

 will appear more strongly, if we omit the months of April and 

 October, which have nearly the mean pressure of the year. We 

 have then a mean for the five mouths of the northerly monsoon 

 or winter period, of 30.178 inches : the mean for January being 

 as high as 30.24 inches. But for the five months of the south- 

 erly monsoon we find a mean of only 29.836 inches ; and the 

 mean of July and August is still lower, being 29.80 inches. We 

 have thus an inequality of 0.342 inch : more than one third of 

 an inch, for the average period of the two monsoons ; while as 

 between January and July and August, in the opposite monsoons, 

 we have the still greater difference of 0.440 inch ; approaching 

 to half a7i inch of the barometric column. I have alluded to this 

 extraordinary inequality of barometric pressure, on a former oc- 

 casion.* 



In regard to the prevalent winds at Canton, and their state of 

 humidity, we perceive that the greater number of rainy days and 

 the greatest depression of the barometer, accord nearly with the 

 period in which the southerly monsoon most steadily prevails. 

 The smallest number of rainy days and greatest atmospheric 

 pressure accord equally with the prevalence of the northerly 

 monsoon. 



At New York, and also at Newfoundland, the tendency of the 

 winds and the distribution of rain, throughout the year, is proba- 

 bly more uniform than at Canton ; but the region about New- 

 foundland is believed to be somewhat remarkable for its humidity, 

 particularly in the summer months ; while, as we have seen, in 

 the latter season the barometer maintains more than its average 

 elevation. 



In view of all the facts presented, therefore, there appears no 

 good reason to ascribe to hygrometric considerations, in any con- 

 siderable degree, the great differences in the equality of atmos- 

 pheric distribution which are here brought to our notice. 



New York, December 3d, 1839. 



* 3.ee this Journal, Vol, xxxiii, p. 264. / 



