234 PREFACE. 
Arborum, why endeavor to increafe their num- 
ber ? Are there not idle people enough already ? 
What fignifies whether Rich a plant be in blow or 
in leaf at the fame time with fome others ; or 
when Rich a bird comes or goes ; Rngs or is 
filent i If we hear the bird Rng, and know for 
what purpofes the plant is ufeful, we know all 
that is necelfary ; every thing beyond that is but 
the wifh, or rather dream of enthufiafm, which 
wants to give an air of importance to its favo- 
rite fubjech This perhaps may be faid by fome ; 
but the fame way of reafoning applied to other 
things will fliew, that it may poffibly be wrong. 
For inRance, the fea fwel'ls twice in 24 hours, 
and the moon pafles thro’ the meridian circle as 
often in the fame time. Now fhould it be faid, 
that if we know each of thefe truths feparately 
it is enough ; and that to know farther what re- 
lation in point of time one of thefe phenomena 
has to the other, is nothing to the purpofe ; i 
believe Rich an affertion would at this time ap- 
pear abfurd, however it might have pafled in ig- 
norant ages. I think we may affert univerfally, 
that whenever two things, however difparate in 
their nature, conftantly accompany one another, 
they are both actuated and influenced by the 
fame caufe. Now that caufe may probably ope- 
rate on other things that lye within the reach of 
our powers, and depend on our determination. 
Thus that conftitution of the air, which caufes 
the cuckow to appear about the time, when the 
fig-tree puts forth its fruit, may indicate the pro- 
pereR feafon to fow fome of our moR ufeful feeds, 
or do fome other work which it imports us to do 
at a right time j and that time niay not be ac- 
cording 
