88 STEUGGLE FOR EXISTENCE. [Chap. in. 



plantations, which were not to be seen on the heath; 

 and the heath was frequented by two or three distinct 

 insectivorous birds. Here we see how. potent has been 

 the effect of the introduction of a single tree, nothing- 

 whatever else having been done, with the exception of 

 the land having been enclosed, so that cattle could not 

 enter. But how important an element enclosure is, I 

 plainly saw near Farnham, in Surrey. Here there are 

 extensive heaths, with a few clumps of old Scotch firs 

 on the distant hill-tops : within the last ten years large 

 spaces have been enclosed, and self-sown firs are now 

 springing up in multitudes, so close together that all 

 cannot live. When I ascertained that these young 

 trees had not been sown or planted, I was so much 

 surprised at their numbers that I went to several points 

 of view, whence I. could examine hundreds of acres of 

 the unenclosed heath, and literally I could not see a 

 single Scotch fir, except the old planted clumps. But 

 on looking closely between the stems of the heath, I 

 found a multitude of seedlings and little trees which 

 had been perpetually browsed down by the cattle. In 

 one square yard, at a point some hundred yards distant 

 from one of the old clumps, I county thirty-two little 

 trees ; and one of them, with twenty-six rings of 

 growth, had, during many years tried to raise its head 

 above the stems of the heath, and had failed. Xo 

 wonder that, as soon as the land was enclosed, it 

 became thickly clothed with vigorously growing young 

 firs. Yet the heath was so extremely barren and so 

 extensive that no one would ever have imagined that 

 cattle would have so closely and effectually searched it 

 for food. 



Here we see that cattle absolutely determine the 



