22 REPORT—1848, 
promoting animalcular life to some extent, and small specimens may be 
seen moving solitary in it. If allowed to stand in a bottle, this may be 
more clearly detected. On this matter I must say more at a future 
time. 
My chief wish is to show that the general notions entertained by persons 
as to the air of towns are not without the support of what is called scientific 
observation, although at the same time the effects on life are greater than 
chemists by any observations could have made out. 
Vogel and others have found organic matter in the atmosphere; and 
Dr. Southwood Smith, in looking for matter which might produce fever, 
found an organic substance, I believe, in some of the streets of London. I 
give only in detail what I have myself observed. 
If this matter should from any cause be exposed to a decomposition more 
rapid than usual, we have before us a state of things worse because more 
general than a bad sewer, and can account for many diseases. I am there- 
fore disposed to think of it as Lord Bacon thought of the cause of jail 
fever :—“ Out of question such smells consist of man’s flesh or sweat putre- 
fied. There may be great danger of such compositions in great meetings 
of people within houses ; for poisoning of air is no less dangerous than 
poisoning of water. And these empoisonments of air are more dangerous 
in meetings of people, because the much breath of people doth further the 
reception of the infection.”—Bacon’s Sylva Sylvarum. 
The state of the air is closely connected with that of the water ; what the 
air contains the water may absorb, what the water has dissolved or absorbed 
it may give out to the air. Whatever the rain meets with in its course from 
the surface to the wells of a town is, if soluble, dissolved in the water. The 
enormous quantity of impure matter filtering from all parts of a large town 
into its many natural and artificial outlets, does at first view present us with 
a terrible picture of our underground sources of water. But when we 
examine the soil of a town, we do not find the state of matters to present 
that exaggerated character which we might suppose. 
I have often been struck with the extent to which water may purify itself. 
At Bala, on the hills, the water is brown; in the lake it is still coloured, 
but in its course it becomes beautifully clear. A still stronger instance 
may be observed on the hills beyond Bolton, the water in which is of a deep 
brown: when it falls into the reservoirs just below it ceases to be very 
dark, although still too brown for agreeable use ; but when it has run a few 
miles it ceases to be remarkable, and is often perfectly pure. I was struck also 
with the fact that filters do not become dirty in proportion to the amount 
of impurity which they seem to remove. The sand at the Chelsea water- 
works contains only 1°43 per cent. of organic and volatile matter after being 
used for weeks, and cannot be considered as impure in a high degree. 
In 1827 Liebig found nitrates in twelve wells in Giessen, but none in 
wells two or three hundred yards from the town (Annales de Chimie, 
vol. xxxv.). Berzelius made similar observations at Stockholm. In 1846 and 
1847 I examined about thirty wells in Manchester, and found none free 
from nitrates; many contained a surprising quantity, and were very nau- 
seous (Mem. of the Chem. Soc.). 
Wells in the country generally contain organic matter, and in the town 
the organic matter is oxidized into nitric acid, as if it required a certain 
intensity to promote the action. It is very probable that this acid is an 
effect of restricted oxidation, occurring as it does with such excess of 
organic matter, and, although near the surface, still under hard pavements — 
