AL. : Proceedings of the British Association 
points Dr. Smith particularly directs attention. Regarding the condi- 
tions of many springs, which never become muddy, but possess a con- 
‘stant brilliancy and a very fae! temperature: at all Soiteins of the year, 
the author thinks that there is a purifying and cooling action going on 
beneath. The surface water.from the same place, even if filtered, has 
not the same brilliancy ; it has-not the same freedom from organic mat- 
ter, neither is it equally charged with carbonic acid or oxygen gas,— 
there are other influences therefore at work. The rain which falls has 
not the purity, although it comes directly from the: clouds ; 3; it may even 
salts; and it is shown by Dr. Smith that their purity is due entirely to 
_, the power of the soil to separate all-organic matter, and: at the same 
time to compel the mixture of cae acid.and oxygen. The amount 
is remarkably pure, and the drainage of the soil is’ such” that there: is 
very little of any salts of nitric acid in it. If the soil,:says Dr. Smith, 
has such a power to decompose by oxydation, we ‘want to know how it. 
gets so much of its oxygen. We must, see look to the air as the * 
only source, and see how it can come tro When water become: 
deprived of oxygen, it very soon takes it ai siete may be prov 
by experiment. This shows us that as fast as the oxygen is: consumed 
by the organic matter, it receives a fresh portion, conveyed to it by the 
' porous soil. Several experiments of the following character were giv- 
best, according to Dr. Smith, as far as clearing the water is con- 
being of steel filings,—oxyd of iron, oxyd of manganese, and 
wdered bricks all answering equally use This shows that the sep- 
aration of the organic matter is due to some peculiar attraction of the 
orous mass presented to the uid. This paper was a 
continuation of Dr. pmb Monet published last year,——and he pro- 
poses continuing the inqui 
On the Proportion of P spor Spotl in some Natural Waters 3 . 
be ake object of this wii was to riche siteiition toa ces ts rce 
; many of our fields may be economically supplied with 
Pi 
a 
