4 THE BOOK OF NATURE STUDY 



heat-giver, and the stretching of a mantle of cloud between us 

 and him means cold, it is yet true that from one day to another 

 the temperature is greatly influenced by the nature of the 

 wind. 



It is obvious, then, that whatever simple form of chart, diagram, 

 or figure we employ for our daily weather observations, we should 

 not be content to say only " windy " or " calm " ; we should add a 

 note on the direction of the wind. It will soon be found that in 

 summer our hottest days generally come with an easterly wind, 

 while in winter the east wind means often intense cold and frost, 

 though the weather is possibly dry and as we say " healthy." 

 When the wind is westerly, again, it is never so cold in winter nor 

 so hot in summer as with an easterly wind, but it is often wet. 

 The class will not have continued its observations long before they 

 will notice that west winds are commonest with us, and that 

 therefore generally our weather is not very cold in winter, and not 

 very hot in summer. 



As to the fourth point, the dampness or humidity of the air, 

 it is well to prepare the way for future observations on evapora- 

 tion and rain formation by simple everyday facts illustrating the 

 variations in the amount of moisture contained in the air. If the 

 air is moist the road is muddy ; if it is dry the road is dusty. The 

 road dries more quickly after rain in summer when the air is warm 

 than in winter when the air is cold. When the air is very moist, 

 the trees, the railings, the walls are all dripping with water ; 

 in summer, especially if it is both windy and warm, the ponds 

 begin to dry up, and the boggy places in the road are no longer 

 muddy. Let your class collect for you little facts of this kind, 

 let them reach themselves the conclusion that sunny days are 

 dry days, that cloudy days are days when the air is moist, and 

 that when the air is moist it rains sooner or later, all these little 

 commonplaces are valuable to them if they have reached them 

 themselves, and the observation of them is paving the way for 

 a fuller treatment later. 



When these simple observations have been continued for 

 some time what have we gained ? We know that it is the sun 

 which sends heat and light to the earth, but that its rays may 

 be partly stopped by cloud. We know that clouds are made 



