SiQ BAROMETUICAL VARIATION* 



Tropical varia- tioiis in a very fraall degree ; and, during the month of Apri^^ 

 tion of the boro- and iq i\^q 20th of May, this fmall tendency of the mercury 

 to perform the motions appeared at times, but was hardly 

 difcernible, the rife and fall being of fo fmall a quantity. 

 From the ISth of January to the 20th ©f May, the mercury 

 in the barometers was in general ftationary, except a very 

 fmall tendency towards the equatropical motions at times, 

 ill t other times fome change in the atroofphere difturbed the 

 mercury from its ftationary pofxtion ; but this was feldom the 

 cafe, as it was then the fair weather feafan, or norlh-eaft 

 nionfoon. 



We failed from Bombay on the 23d of May, 1803. The 

 inflant we got out of the harbour, the mercury in the baro- 

 meters conformed to the equatropical motions with great re- 

 gularity, and the difference between the high and low ftations 

 was very confiderable during the whole of the paflTage to 

 China, excepting a few days in the eaftern parts of Malacca 

 Strait, where the land lay contiguous on each fide of us ; the 

 difference between the high and low ftations of the mercury 

 was not then fo great as in the open fea. On clearing the 

 Strait, and entering the China Sea, the equatropical motions 

 were performed in greater quantity, and continued regular 

 during our paffage up the China Sea, until July 2, 1803. We 

 then entered Canton river, and the equatropical motions of 

 the mercury in barometers entirely ceafed. 



From July Sth to September 7th, the barometers were 

 placed on fhore in Canton, during which time the mercury 

 appeared to have no tendency towards performing the equa- 

 tropical motions; but it inclined to a ftationary pofiiion, ex- 

 cept when influenced by changes of weather. After the ba- 

 rometers were taken from Canton to the (hip, we were four 

 days in getting clear of the river, in which time the mercury 

 inclined to be ftationary, excepting that a fmall inclination 

 towards the equatropical motions feemed to evince itfelf at 

 times. But no fooner had we cleared Canton river, Sep- 

 tember 13, 1803, than the mercury in the barometers began 

 to conform to the equatropical motions, of two elevations and 

 two depreffions every 2i hours, at equal intervals of time, 

 (although we were near the land until the 15th September.) 

 And the mercury, with great regularity, continued to per- 



forni 



