9 
new forms, the destruction of one order of beings 
tends to the conservation of another ; solution and 
consolidation, decay and renovation, are connected, 
and whilst the parts of the system continue in a 
state of fluctuation and change, the order and 
harmony of the whole remain unalterable. 
After a general view has been taken of the na- 
ture of the elements, and of the principles of che- 
mical changes, the next object will be the structure 
and constitution of plants. In all plants there 
exists a system of tubes or vessels, which in one 
extremity terminate in roots, and at the other in 
leaves. It is by the capillary action of the roots 
that fluid matter is taken up from the soil. The 
sap in passing upwards becomes denser, and more 
fitted to deposit solid matter : it is modified by 
exposure to heat, light, and air in the leaves ; de- 
scends through the bark, in its progress produces 
new organized matter ; and is thus, in its vernal and 
autumnal flow, the cause of the formation of new 
parts, and of the more perfect evolution of parts 
already formed. 
In this part of the enquiry, I shall endeavour to 
connect together into a general view, the observa- 
tion of the most enlightened philosophers who have 
studied the phisiology of vegetation. Those of 
Grew, Malpighi, Sennebier, Darwin, Decandolle, 
Mirbel, and above all of Mr. Knight. He is the 
latest enquirer into these interesting subjects, and 
his labours have tended most to illustrate this part 
of the economy of nature. 
The chemical composition of plants has, within 
the last ten years, been elucidated by the experi- 
