On the Water of Tunbridge Wells. 347 
veniencies would be equally benefited by being made acquainted 
with the cause of the hardness, provided the carbonic acid were 
found, upon experiment, to be the sole cause of it, for I need 
scarcely add that other acids, combined and free, are also the 
cause of the hardness of waters, by disengaging the alkali from 
the oil in soaps. I therefore, with no little alacrity, set to work 
to ascertain the fact, and I was soon confirmed in the correctness 
of the opinion I had formed. 
I took some of the water, not recently drawn from the well, 
but which had remained in an open cistern twenty-four hours, 
and poured it into a stone filtering jar; this jar is divided into 
three compartments, the top one in which the water is first 
piaced, the centre one into which a piece of sponge is pretty 
tightly crammed, the bottom of this division being pierced with 
pin-holes to suffer the water to escape into the third compart- 
ment below, after it has past through the sponge. Upon mix- 
ing soap with some of the water filtered in this simple, easy, 
and expeditious way, I was extremely well pleased to find that 
it was become soft. I was now, therefore, sure that the incon- 
venient degree of hardness was owing to the carbonic acid ; but 
being desirous that a more able and experienced chemist should, 
in a better way, ascertain, beyond doubt, the ingredients of the 
water thus filtered, 1 brought some of it to town and requested 
Mr. Faraday, of the Royal Institution, to analyze it, and he 
very obligingly sent me the following satisfactory answer. 
Royal Institution, 
October 10, 1822. 
Sir, 
I have examined the water attentively, and find xo tron in it. 
It is by no means abundant in saline matter, containing only a 
little muriate and sulphat of soda and lime. There is no car- 
bonic acid or magnesia in it. 
I am, &c. &e. 
Upon ascertaining the fact that the hardness of the water 
depended upon the carbonate of iron from which it might be 
freed by not being immediately used when drawn, and by sub- 
