1834.] Range for the Culture of the Tea Plant. 179 



The climate of the whole of China is remarkable in respect of tem- 

 perature, and it must be duly weighed when the acclimatization of any 

 of its peculiar vegetable productions in another country is concerned. 

 Latitude alone is here no guide, the mean annual heat being much under 

 what is observed in most other countries at an equal distance from the 

 equator. Pekin, lat. 39° 54', nearly at the level of the sea, has a mean 

 annual temperature of 54.36 ; calculated for the latitude theoretically by 

 a formula* of very general application for the distribution of heat ac- 

 cording to latitude without reference to other modifying causes, we get 

 62° 5' ; — a difference of about 7°. 5 above the observed mean temperature 

 of the year. But it is in the excesses of the summer and winter seasons 

 that the climate is most remarkable. It has a winter temperature of 

 26° .42, or nearly that of Upsal in lat. 59° 51' (20° further north) and a 

 summer heat of 82°. 58. Its winter climate is that of Copenhagen, and 

 its summer heats are as scorching as at Cairo. Between the mean 

 temperature of the hottest month in summer and the coldest of winter, 

 there is a difference of not less than 59° of Fahr., a climate of excesses 

 almost without parallel in any part of the globe except Quebec in 

 Canada. This condition, which is owing to the vast accumulation of land, 

 extending from the arctic pole on through eastern Asia to China, is not 

 confined to the northern provinces. It extends to Canton within the 

 tropic, but modified there by the equalizing effect of a now tropical ocean 

 about it. The mean annual heat of Canton, lat. 22° 10', calculated 

 theoretically for this latitude, gives 7 5°. 5, Fahr. ; reduced from a regis- 

 ter in the Transactions of the Medical Society of Calcutta, the observed 

 mean temperature is 73° nearly. The mean of the coldest winter month 

 is 54° ; of the hottest summer month 85°. 5. I am not aware that any 

 determination has been made of the climate in the provinces between 

 Pekin and Canton, and I have not access to the later writers on China. 

 But an approximation may be made to the temperature of the tea dis- 

 tricts from the facts known regarding Pekin and Canton. Assuming 

 that the most productive tea districts extend from 27° to 31° N. lat. 

 and taking 29° as the central tract, by calculation for this latitude we 

 get 71° Fahr. for the mean annual heat at the level of the sea. As- 

 suming further, that the refrigerating influences on the climate of China, 

 which have been seen to be 7°. 5 at Pekin and 2°. 5 at Canton, amount 

 to 5° Fahr. in the parallel of 29° lat., and deducting this from 71°, we get 

 66° for the mean annual temperature. The elevation of the tracts of 

 tea cultivation above the sea will form another abatement on this sum. 

 But on this point I have no grounds to form any thing like a precise 



* Mean temperature=81 Cos. Lat. 

 t Vol 6t'a, by Mr. Pearson. 



