18 NATURAL CONDITIONS OF PLANTS. 
“ If the laws of Nature, on the one hand, are 
invincible opponents, on the other, they are irre- 
sistible auxiliaries ; and it will not be amiss if 
we regard them in each of these characters, and 
consider the great importance of them to man- 
kind : — 
“ Firstly. In showing us how to avoid attempt- 
ing impossibilities. 
“ Secondly. In securing us from important mis- 
takes in attempting what is in itself possible, by 
means either inadequate, or actually opposed to 
the ends in view. 
“ Thirdly. In enabling us to accomplish our 
ends in the easiest, shortest, most economical, and 
most effectual manner. 
“ Fourthly. In inducing us to attempt, and en- 
abling us to accomplish objects, which, but for 
such knowledge, we should never have thought of 
undertaking.” — Herschel. 
