INFLUENCE OF CLIMATE ON PLANTS. 
37 
other celestial luminaries appear to be either incapable of generating it, or are too 
far removed from us to render any emission of it perceptible from the rays which 
reach our globe. Indeed, the moon may be supposed rather to possess the power 
of attracting and abstracting it, for we have repeatedly remarked that frosts are 
most severe (and frequently occur only) when the moon's disk is visible, and parti- 
cularly when she is in the latter quarter of her revolution. During the period 
immediately succeeding the spring and autumnal equinoxes, when the moon rises 
unobscured, in a calm atmosphere, after twilight in the evening, it is almost 
invariably accompanied by a greater or less degree of frost : and when it is not 
seen above the horizon till near or after midnight, this is still more frequently the 
case. Hence it is that many tender plants have been injured in the morning at 
this period, because the atmosphere was not sufficiently cold at night to induce the 
cultivator to protect them, he being at the same time ignorant of the above facts. 
Now we know that the absence of wind and clouds would alone facilitate 
radiation from the ground, and that the temperature of the earth's surface is always 
lower after midnight, on account of the prolonged absence of solar rays, and the 
protracted radiation ; but the result of our observations is not confined to this period. 
On the contrary, we have noted the occurrence of the same phenomena when 
the moon was far advanced in the second quarter, and consequently when she rose 
before sunset. Frosty evenings at this period have very frequently been succeeded 
by rainy mornings, after the declension of the moon ; while precisely the reverse 
has occurred in the later stages of the lunar revolution. This hypothesis receives 
additional strength from the circumstance of frosts invariably being much slighter 
in those situations which are by any means shaded from the lunar rays ; and 
which, by their distance from the bodies which sheltered them, cannot be supposed 
to derive any heat from them, or to be at all assisted by them in retaining their 
temperature, otherwise than by their refracting the moon's beams. We do not, 
however, profess to assert this as an established principle, or one that is not liable 
occasionally to be departed from ; but it certainly appears to us to be founded 
in reason, and supported by facts : it is therefore well deserving of the unbiassed 
attention of the inquiring gardener. 
Cold — the direct converse of heat — is by many ignorantly considered a distinct 
principle, or entity. So far from this being the case, it is merely the state pro- 
duced by the abstraction or absence of heat ; in fact, a consequence, and not a 
cause ; a condition, and not a constituent. When we say, therefore, that certain 
plants are injured by cold, although the mode of expression appears to imply that 
cold is an active agent, we must be understood to mean that the injury is occa- 
sioned by the excessive radiation of heat from their substance, on account of its 
distributive property. It will thus be perceived that the effects of cold are due to 
the withdrawal, and not the introduction, of an element : and that the tempera- 
ture of those bodies which radiate heat most rapidly, is more speedily reduced to 
the medium of the surrounding atmosphere. 
( To be continued.) 
