DECEMBER 313 



tinues to radiate or part with more heat than the sun is 

 able to give it. This is liable to modification by varying 

 atmospheric conditions. Thus, if in December clear skies 

 preponderate over clouds, radiation will go on faster, 

 causing the mean temperature to fall lower, than in a 

 cloudy January. Under a cloudy sky the heat radiated 

 from the earth is reverberated from the cloud canopy, 

 keeping the intervening atmosphere warm. If you leave 

 a table out upon the lawn during a clear, still winter 

 night, the grass around will all be white and crisp with 

 hoarfrost in the morning ; but under the table it remains 

 soft and green. The heat radiated from that fraction of 

 the earth's surface cannot escape into space; it strikes 

 the under side of the table, and is returned whence it 

 came, radiation and return going on until the surround- 

 ing atmosphere has become so bereft of heat as to flow 

 into the protected space. 



Although it is vain to reckon the turn of the year 

 as corresponding with the passage of the shortest days, 

 certain living organisms respond to a vivifying influence 

 of which we grosser creatures are utterly insensible. 

 While we are piling fresh logs to combat the growing 

 cold (or to put it more scientifically, to replace the waning 

 heat), a few humble herbs are on the point of developing 

 their supreme vitality. Among these, the most familiar 

 to dwellers in the west is the snowdrop, probably not 

 a true native of any part of the British Isles, but a 

 colonist which has established itself in multitude wher- 

 ever a cool soil and moist climate combine to encourage 

 it. In certain westland woods it occupies many acres, 

 making a marvellous display in January and February, 



