PHYSICAL CLIMATE. 



497 



identity between the temperature of the caves of the Observatory of Paris at about 85 feet 

 below the surface, and the mean of the annual extremes. " We may regard, " he 

 remarked, " the air of the caves as the mean state of the climate." "Where this method is 

 impracticable, one daily observation of the thermometer through the year at the surface 

 is in many places sufficient, because at a certain period of the day it has been found by 

 experience to stand at the daily average temperature. In our own country, the thermo- 

 meter is thought to give the mean heat for the day at about a quarter or half past eight in 

 the morning. According to Humboldt also, the mean temperature for the months of 

 April and October are very nearly equal to the annual mean temperature, the latter month 

 making the closest approximation, a highly important remark for travellers to bear in 

 mind. The temperature of the year, he states, is found at Buda in Hungary, from the 

 15th to the 20th of April, and from the 18th to the 23rd of October. The close 

 approximation of these months to the mean annual temperature appears in the annexed 

 comparison : 



In almost all northern latitudes, January or February is the coldest month of the year, 

 and July or August the warmest. The greatest cold during the day is usually about an 

 hour before sunrise. The greatest heat in latitudes between 35 and 60 is from two to 

 three o'clock, and from one to two o'clock between the equator and 35. 



The mean temperature of different months, in various places, takes a very wide range 

 above and below the mean annual temperature, and constitutes what Buffon has indicated 

 by the name of " excessive" climates, where the winter and summer are in violent contrast. 

 These are chiefly found in North and Eastern Europe, in Asia and America. 



The climates of the Atlantic region of the United States, and of the northern part of 

 China, are among the most " excessive," the winters and summers strongly contrasting 

 in their temperature. Thus, at New York, says Humboldt, we find the summer of Rome 

 and the winter of Copenhagen. At Quebec, grapes sometimes ripen in the open air, 

 whereas the winter is that of Petersburgh, during which the snow lies five feet deep for 

 several months, and travelling is performed in sledges, frequently on the ice of the 

 St. Lawrence. At Pekin in China, where the mean temperature of the year is that of 

 the coasts of Brittany, the scorching heats of summer are greater than at Cairo, and 

 the winters as rigorous as at Upsal. These violent contrasts render such climates 

 trying to the constitution of a western European, unused to such extremes of temperature, 

 the excessive heat of summer, after the rigour of winter, increasing the irritability of the 

 nervous system. 



K K 



