CHAMBERS'S INFORMATION FOR THE PEOPLE. 



use for illustrating the effects of climate on crops. 

 The mean may be made up by a wide range of 

 temperature, or the reverse. Thus, a mean of 60 

 may be made up of a maximum of 75 and mini- 

 mum of 45, or a maximum of 65 and a minimum 

 of 55. Such atmospheric conditions, however, 

 would be attended with different effects on the 

 soil and plants. Did our space permit, we would 



shew that the mean maxima and mean minima 

 temperatures put us in possession of data to esti- 

 mate the effects and intensity of many climatolo- 

 gical influences. The following are the mean 

 maxima and mean minima temperatures in the 

 different months at a few stations which, being 

 calculated for the same thirteen years namely, 

 1857 to 1869 are comparable inter se. 



TEMPERATURE. 



The highest summer day temperature occurs in 

 the district round London. Wheat is cultivated 

 with great success in Morayshire (Elgin) ; but the 

 northern limit of cultivation of this cereal extends 

 only a little to the north of this ; hence the mean 

 day temperatures of this place possess great value, 

 as indicating the approximate limit of the profit- 

 able cultivation of wheat. At Sandwick, wheat 

 and barley do not ripen properly, the region of 

 the cultivation of these cereals being now passed. 

 The temperature of 40, or rather 39 -2, the 



maximum density of fresh water, is an import- 

 ant temperature with reference to vegetation 

 experience having shewn that little vegetation 

 takes place when the temperature of the nights 

 falls to 39-2. In this respect, the table is of great 

 value. 



The quantity of rain which falls in different 

 districts is another important point. The table 

 below gives the amount of rain in inches at the 

 following stations, with the number of years for 

 which the averages have been calculated. 



RAIN. 



More rain falls on the west coast than on the 

 east ; but it is worthy of observation that the ex- 

 cess is principally confined to winter and autumn. 

 In the eastern and central counties of England 

 and Scotland, where the annual rainfall is small, 

 most rain falls during the warm months ; but 

 the evaporation being great, the climate is 

 then dry. At western stations, the autumnal 

 rains set in earlier than in the east. In the 

 north of Great Britain, the driest period of the 

 year is the month of May ; but in the south 

 and south-east, this occurs at least two months 

 earlier. 



From these tables, the distinguishing peculiari- 

 ties of climate in different parts of the British 



518 



Islands are apparent. The warmer nights and 

 cooler days of Cornwall give as high a mean as 

 the cooler nights and warmer days in Middlesex. 

 Even when the fall of rain is the same at two 

 places, the effects of this different composition 

 very marked upon crops, inasmuch as the rang 

 of temperature determines to a considerable 

 tent the force of evaporation. 



The drying or evaporating power of the atmos- 

 phere is also an important matter to be attended 

 to. The range of the thermometer is less on 

 mountains than in valleys, and, consequently, 

 corn is always more difficult to harvest on nig! 

 grounds, owing to the diminished evaporatic 

 (See METEOROLOGY.) 



