PREFACE. 



JL he utility of such a work as this cannot, we pre- 

 sume, be doubted, while the sciences of Botany and 

 Agriculture are so liberally encouraged. We are 

 happy to boast the friendly assistance of men of the 

 first abilities, whose encouragement cannot but be an 

 honour to us. The undertaking was begun at a time 

 when we had but just become aware how far we were 

 behindhand in this most essential knowledge, when 

 even the Diamond, one of the oldest jewels in the 

 known world, had but recently been discovered to be 

 pure Carbon*. Discoveries, scarcely less remarkable, 

 are continually making. 



The use of figures to illustrate a subject not gene- 

 rally understood, and which it requires so much study 

 to bring to perfection, will be every day more and 

 more apparent 5 and we have been flattered by the 



* See page 106. 



