114 
UPWARD GROWTH OF THE HEAD, AND [Part II. 
flat a contradiction in terms as to say that light 
is caused by darkness. 
It is, indeed, the part of a thorough philo¬ 
sopher not to wonder at any thing. Those who 
have no pretence to that character must wonder 
at every thing ; and, among others, at the. at¬ 
tractive force of gravity. Why a stone when 
dropped from the hand in the air should fall to¬ 
wards the centre of the earth is, of itself, a most 
unaccountably marvellous fact. But this is in 
unison with our universal, every-day experience; 
and the philosophic may not, and the unphilo- 
sophic do not, wonder at it. But how infinitely 
more unaccountably marvellous would it be if, 
owing to the same force,—gravity, one half of 
the stone were to fall towards the centre of the 
earth, and the other half were to fly off in the 
exactly opposite direction ; that is, towards the 
zenith! As this would be contrary to our uni¬ 
versal, every-day experience, possibly the phi¬ 
losophic, certainly the unphilosophic, would 
wonder at it. Yet if we refer the direction 
of the vertical growth of plants to gravity, this 
is precisely what does take place: namely, the 
first start of the root is with the attraction of 
gravity towards the centre of the earth ; the 
first start of the stem is against it, in the exactly 
