36 VARIATIONS OF TEMPERATURE. 



lowest range of the thermometer as given in the 

 Appendix, we shall be surprised at the little variation 

 which really occurs, at least in the south. The 

 variation of temperature which takes place in the 

 course of a day, and from day to day in England, 

 is frequently greater than that which happens 

 during a whole month at Canton and Macao. The 

 greatest variation occurs during the N.E. monsoon, 

 the monthly mean of which may be stated at 25°, 

 while that of the S.W. monsoon is about one half 

 or 13°. The mean variation of the three coldest 

 months may be stated at 30°, while the three 

 hottest months, June, July, and August, exhibit 

 only 11°. On some occasions at Canton, and ap- 

 parently throughout the empire, a depression of 

 thirty or more degrees has taken place within 

 twenty-four hours. But these great changes of 

 temperature are rare, and happen only during the 

 N.E. monsoon, when the season of cold and dryness 

 prevails, and vegetation is at rest. Indeed, the 

 few vicissitudes of temperature to which vegetation 

 is exposed during the period of its greatest activity 

 from spring to autumn, when stimulated by the 

 combined action of heat, bright sunshine, and 

 moisture, and the uninterrupted dryness of the 

 atmosphere, with some few exceptions on the sea- 

 coast, during the winter season, may account, at 

 least in an eminent degree, for the varied and 

 widely extended distribution and intermixture of 

 inter and extra tropical products over this vast 



