on the Temperature of Soils. 
135 
is the same as that given by Pliny and Plutarch ; but they attributed 
the origin of this immediate cause, the additional moisture, to the pe- 
culiar humefying quality which they supposed that luminary to possess. 
This false theory has probably contributed to discredit, with the moderns, 
the circumstance which it was employed to explain." — Essay on Dew. 
The belief that moonshiny or clear and dewy nights advance 
the process of putrefaction is not altogether confined to the an- 
cients or to tropical climates, as was supposed by Dr. Wells. I had 
personally noticed the phenomenon of an increased putrefactive 
vigour in dungheaps, after nights of a copious precipitation of 
dew, succeeded by hot days, some years before I was acquainted 
with Dr. Wells s ' Essay ;' and I frequently conversed on this 
subject with an intelligent and observant farmer near Warwick, 
who corroborated mj idea that such was the fact. Several far- 
mers have recently confirmed this early opinion ; and it is very 
common in France, among the numerous peasant-farmers near 
Paris. During a residence of several years in that country, my 
house being surrounded by small, unenclosed, and variously- 
cropped plots of ground, with a heap of night-soil or dung usually 
contiguous to each, the sense of smell somewhat too frequently 
informed me of extreme activity in the putrefactive process. On 
inquiring of the peasants how it happened that, on certain morn- 
ings, the odour was so pungent, they commonly replied, " It is 
owing to the dew of last night. Sir ;"' but I do not recollect that 
any one of them imputed the effect to the moonbeams. 
A knowledge of all that is requisite for the perfect preparation 
and management of dung is yet a desideratum in agriculture. 
Means of accelerating and retarding, at will, the putrefactive 
process, are much needed. The study of this art is certainly 
worthy of closer attention, and more exact experiment, than it has 
yet received. A movable roof-shelter might be a useful adjunct 
to the sunken pit, or raised mass, in order to obtain command 
over the meteorological agents — air, heat, and water ; each of 
which performs a part in the process ; and more frequently to the 
injury than to the benefit of that species of manure which 
home-made, and the most natural, if not the most beneficial, to 
the farmer. 
"1 had often," says Dr. Wells, " in the pride of half-knowledge, 
smiled at the means frequently employed by gardeners to protect tender 
plants from cold, as it appeared to me impossible that a thin mat, or any 
such flimsy substance, could prevent them from attaining the tempe- 
rature of the atmosphere, by which alone I thought them liable to be 
injured. But, when I had learned that bodies on the surface of the 
earth become, during a still and serene night, colder than the atmos- 
phere, by radiating their heat to the heavens, I perceived immediately 
a just reason for the practice, which I had before deemed useless," 
