XXII. 



man's work on the farm, 



Hitherto we have been considering how the world's 

 fields are cultivated when the work is left entirely to 

 those who labour without hands — to air, wind, frost, 

 rain, snow, sun, glacier, river, earthquake, volcano ; to 

 the worms and others which plough the soil ; to the 

 insects which act the part of pollen-carriers between 

 the flowers, and to the birds which keep the insects in 

 order, and help the winds and waves to scatter the 

 seed. These and many other workers not here enu- 

 merated, are at work constantly in the fields which 

 man has taken under his own care, as well as in those 

 still left entirely to nature. Together they keep the 

 world green, and they would keep it green if there 

 were not a man in it ; for they are quite able to do 

 without his help in the matter, though he would be 

 entirely helpless without theirs. 



But man has done much to modify the result of their 

 combined labours, not only in that small proportion of 

 the earth which he cultivates or occupies, but even 

 beyond. Where men dwell together in numbers, there 

 the earth is necessarily less green, for towns, cities, 

 roads, railways, have invaded the woods and fields, and 



22 



