134 
On the Iiifluence of Water 
Popular belief is often founded on correct observation, and 
sound practice is not unfrequently in advance of science. It also 
not uncommonly happens that the evidence of practical truths is 
received with scepticism, because we are unable, immediately, to 
" interpret nature," and frame a satisfactory theory or explanation 
of the origin of particular phenomena. Hence the discovery of 
causes is of the highest importance to the arts, and a correct 
theory of any action so rapidly accelerates, extends, and perfects 
sound practice, that we cannot too highly prize its possession. 
This admitted truth, together with the rarity of Dr. Wells's ' Essay,' 
will, I trust, form a sufficient excuse for introducing the mention 
of phenomena explained by his theory of dew, which, though not 
directly affecting the soil itself, are of no slight consequence to 
the cultivators of the soil : — 
"The bare mention of this article," Dr. Wells observes, "will be 
apt to excite ridicule, it being an attempt to show in what way the 
exposure of animal substances to the moon's light promotes their 
putrefaction. 
" I have no certain knowledge that such an opinion prevails any- 
where at present, except in the West Indies ; but I conclude, from 
various circunistances, that it exists also in Africa, and that it was car- 
ried thence by negro slaves to America. It was entertained, however, 
by persons of considerable rank and intelligence among the ancients ; 
for Pliny affirms it to be true, and Plutarch, after making it a subject 
of discussion in one of his Symposia, admits it to be well founded. 
" As moonbeams communicate no sensible heat to the bodies on 
which they fall, it seems impossible that they can, directly, promote 
putrefaction. But still a reason for ascribing such a power to them 
may be derived from their being received by animal substances at the 
verv time that a real but generally unnoticed cause of putrefaction in 
warm climates (and it is in these alone the opinion I am treating of has 
ever prevailed) is taking place, which ceases to act as soon as the moon's 
light is excluded. 
"•The nights on which a steady moonshine occurs must necessarily 
be clear, and nights which are clear are almost always calm. A moon- 
shiny night, therefore, is one on which dew forms plentifully ; hence 
the expressions 'roscida' and ' rorifera luna,' employed by Virgil and 
Statins ; and hence also an opinion, held, as appears from Plutarch, 
even by philosophers among the ancients, that the moon communicates 
moisture to the bodies which are exposed to its light. 
" Animal substances are among those which acquire dew in the great- 
est quantity. To do this, indeed, they must previously become colder 
than the atmosphere ; but, having acquired the moisture of dew, in 
addition to their own, they will, on the following day, be in that condi- 
tion which is known by experience to favour putrefaction most power- 
fully in hot climates. 
" The immediate cause assigned here for the putrefaction of animal 
substances which have been exposed to the moon's rays in a hot country, 
