LETTER XVIII. 



" The provisions of Nature in the constitution of each individual 

 of the human species are not confined to his own immediate wants : 

 they extend to his adaptation for social intercourse ; to the relief 

 of his sufferings by the sympathy, and the increase of his enjoyments 

 by the participation of others, and to the cordial union and co-ope- 

 ration of numbers in prosecuting objects and surmounting difficulties 

 for which the exertions of individuals would be inadequate." 



William Pulteney Alison. 



" No sin his face defiling, 



The Heir of Nature stood, 

 And God, benignly smiling. 

 Beheld that all was good ! 



Yet in that house of blessing, 



A single want was known ; 

 A wish the heart distressing ; 



For Adam was alone ! " 



Reginald Heber. 



" Amid Nature's infinitely diversified productions, we find but 

 one original model or pattern." Dr Edward Hitchcock. 



August 18, 1855. 



My Dear Sons, 



1. In bringing to a close my argument with Dr 

 Carpenter, and, with it, the whole proof and defence 

 of my theory of trees, I will venture to suggest and 



