MIXED CltOP OP UNIFORM AGE. 55 



rest during the prevalence of the predominating temperatures, and 

 so on. 



Absolutely speaking the effects of frost will be severer 



(1) In level than in hilly country, since, the elevation being one 

 and the same, radiation will be more unchecked and, therefore, 

 more rapid in the former case ; 



(2) On southerly and easterly than on northerly and west- 

 erly slopes, since on the former the sun shines as soon as it is 

 above the horizon and hence causes sudden thaw ; 



(3) At the bottom of valleys than on the overhanging slopes, on 

 which the air is in more constant movement and the young shoots 

 of the trees are smaller and less sappy and more quiescent; also be- 

 cause the cooled andltherefore heavier air from the open elevated 

 sides and ridges flows down into the depressions and collects there; 



(4) In confined places where the air is still than in breezy or 

 windy localities; 



(5) In places exposed to chilly winds than where such winds 

 cannot enter ; 



(6) In a mild climate, with a long season of vegetation, such as 

 we have everywhere in India outside the very high mountain ran- 

 ges, than in a severe climate, since in the former the young shoots 

 will always be more herbaceous and watery and will be less likely 

 to be in a qiu'escent state, and the frost will occur chiefly at night, 

 after and immediately before the action of a hot and, therefore, 

 also forcing sun ; 



(7) In a dry than a moist atmosphere, since there will be less im- 

 pediment there to radiation; 



(8) In a moist than in a dry soil, the same result taking place 



here as in (6) ; 



(9) In a sandy than in a clayey soil, since sand radiates more ra- 

 pidly than clay; 



(10) On a grass-covered surface than where the soil is bare, silica 

 the numerous small surfaces presented by the leaves and stalks of the 

 herbage will aggregate together a much larger radiating surface 

 than the naked superficies of the ground ; 



(11) At the surface of the earth than at any height above it: 

 meteorological observations taken at the Forest School and in the 

 Dehra Dun forests show a difference of sometimes as much as 5 D 

 Fall, between thermometers placed at 5 and 60 feet respectively 

 above the ground ; 



(12) In a shallow soil or one difficult to penetrate for roots than 

 in one in which the roots can go down easily (see page 49). 



