THE BEECH. 



333 



A fourth cause of the coohiess of the air in a 

 wood^ dependent on those already mentioned, 

 may, and probably does, also exist, though I have 

 never had an opportunity of testing the efficacy of 

 this. On the outside of the wood, the air nearest 

 to the ground would naturally be the warmest, 

 and would consequently rise into the upper re- 

 gions. Colder air from the wood would rush out 

 to supply the place of that which had ascended, 

 and thus a light breeze would be produced, con- 

 stantly setting from the centre of the grove to its 

 circumference. On this theory we are to ac- 

 count for the superior stillness of our summer 

 nights over the days, the temperature during the 

 absence of the sun being more nearly equalised. 



This may seem a long and uncalled for digres- 

 sion ; but I am unwilling to pass by any oppor- 

 tunity of drawing the attention of my readers to 

 those instances of design on the part of our 

 Heavenly Father, which, though mainly instru- 

 mental to the production of other efiects, are 

 greatly conducive to the comfort and enjoyment 

 of mankind. In the present instance we have a 

 striking example of several of the more secret 

 operations of Nature, each exercising a peculiar 

 influence of its o^^ll, yet all harmoniously com- 

 bining to produce an effect appreciable by us, and 

 contributing to our advantage. Were we to look 

 on them in another aspect, we should find each 

 cause combining with others to further some 



skirts tlie higtLway road, rather than on the road itself, the combined 

 effects of radiation and evaporation rendering the grass cooler to the 

 feet. In a winter's morning we prefer the dry road, radiation of 

 heat from the blades of grass having reduced them to so low a tem- 

 perature, that they are covered with dew or hoar-frost condensed 

 from the warmer atmosphere around them. 



