OF GROWTH IN TREES. 103 



this connection : that sensation links us with matter, is the germ 

 of intellect, and the avenue of human knowledge. 



Notwithstanding the unbounded liberty which the mind of 

 man seems to possess, it is in reality confined within very nar- 

 row limits ; for when we carefully analyze our ideas, simple and 

 complex, we can trace them without an exception to past im- 

 pressions made on our organization. We can form no con- 

 ception of anything without a reference to ideas previously 

 acquired. I may conceive of a golden mountain, but it is 

 obvious that if I had not previously acquired, by impressions 

 from external Nature, the ideas of mountain and gold, it would 

 have been impossible to have formed the combination. 



"We are very frequently compelled to receive ideas independ- 

 ently of our will. I may, for instance, be looking out of my 

 window, and see a man shot down, and a year afterwards recol- 

 lect the circumstance. I have thus involuntarily acquired an 

 idea. Impressions thus received, when powerful and painful, 

 will recur again and again, and influence our conduct through 

 life. 



Now if our knowledge of an external object was limited to 

 the moment of perception, and was extinguished forever with 

 the fading sensation which gave it birth, if we had no memory 

 of past impressions, then we should be creatures utterly inca- 

 pable of reasoning or reflection. But we are so constituted 

 that the knowledge derived from without lives within us. All 

 our past impressions are secured to us. They are associated 

 together according to certain laws, which have evidently been 

 contrived with the most admirable adaptation to our wants, so 

 as to bring again the knowledge previously acquired by the 

 senses at the very time when its return is the most profitable. 

 "A burnt child fears the fire," for example. Hence we are ever 

 expanding ourselves over the long series of our past sensations, 

 for memory is the mind relapsing into a former state, and the 

 use of reason becomes more and more apparent as these sensa- 

 tions from the external world are increased in number and 

 variety. 



How beautifully are the upper and lower extremities of a 



