20 REPORT—1848. 
wherever there is a reservoir of putrid matter, for then the exhalations 
are also abundant, and bubbles may be seen to rise from filthy water. It 
is not improbable that the state of the atmospheric pressure may cause this, 
as Mr. E. W. Binney has shown that the gases in coal-pits are caused to 
escape rapidly during a lowering of the barometer. Bodies that are 
moist will therefore give out more organic vapours; if there be abun- 
dance of water, as in a lake, the vapours would to a great extent be dis- 
solved, even if the same kind of decomposition were to proceed as in merely 
moist or marshy ground. We might expect then that soil, if moist, will 
give out, not pure vapour of water, but water with organic matter in it. 
Wet soil is a little acid generally, and if very acid is bad land, sour as it is 
called ; but if made alkaline either by the direct adding of ammonia, or by 
decomposition producing ammonia, it becomes fertile. If any alkali be 
added which gives out ammonia by decomposing the humate of ammonia in 
the ground, the same state of fertility is attained. This end is generally 
attained by adding lime. This state of almost neutrality of the soil is also 
regulated by nature, and a fertile alkalinity obtained by the rapid decompo- 
sition of organic matter through moisture and heat. In this alkaline and 
warm state more vapours will of course be given off, and the ammonia will 
assist in the removing of organic matter into the air. How far this occurs 
on sowed land has not yet been seen by me satisfactorily ; but on peat land 
the ammonia formed is abundant in hot weather, so much so as to be per- 
ceptible directly by the senses, and to take with it in solution a large quan- 
tity of humus and salts of humus, containing food for plants, as I showed in 
a paper to the Philosophical Society of Manchester. 
I mention this to show how organic matter may be lifted into the air, 
and why hot weather promotes it; also I wish to show how various this 
matter must be in its properties, as all vegetable solutions give out a certain 
amount of matter from them. 
To ascertain if organic matter were really to be got from such vapours 
from land, I collected some dew by condensing it on a glass cylinder, and 
allowing it to drop into a glass below. ‘The fewness of the evenings fa- 
vourable for the purpose this year has of course retarded me. I saw plainly 
however that the substance thus obtained from the dew was very different 
from that obtained by condensation in a warm room; whereas that from a 
crowded room was thick, oily, and smelling of perspiration, capable of de- 
composition and productive of animalcules and conferve ; the dew was 
beautifully clear and limpid. When boiled down the odour was not dis- 
agreeable, and I may say not remarkable; but when the small portion of 
solid matter which remained dissolved in it was exposed to heat, the smell 
was that of vegetable matter with very little trace of any nitrogenized 
substance. It was also rather agreeable than otherwise. The dew was 
collected in a flower-garden, and I have no doubt in favourable weather of 
being able, in dissimilar situations, of getting it of different characters. It is 
not improbable that the matter in the dew may be a measure of the amount 
in the atmosphere ; if so, the decided difference between that of the country 
and that of crowded rooms is to be remarked, and may probably form a 
good guide towards a knowledge of comparative purity of atmosphere. 
eee esse beta ie 
In walking along the fields on an evening when there is much dew, it — 
may be observed how much effect a dry soil has; indeed I might almost — 
say the climate of a field will be found to vary almost every yard. Every — 
cause of cold, the formation of a drain, the lowness of any spot, its being 
4 
higher or more level or more sheltered, is indicated by this delicate ther- 
ten 
