B2 Filtration of Water ; 
No. 7. 
JV ® ew Method of applying the Filtering Stone for purify- 
ing Water . By Mr. William Moult. 
[With an engraving.) 
Sir- — I f you think the following information, relative to 
a new method of filtering water, is deserving of the atten- 
tion of the Society of Arts, &c. I wish you would lay it 
before them. My objections to the old method of filtering 
by putting water into the filtering stone are, that the dirt 
falls to the bottom, and fills up, or chokes the pores of the 
filtering- stone, so that the stone requires frequently to be 
cleaned with a brush and sponge to allow the water to 
pass, after which the water passes through the stone in a 
muddy state for two or three days ; it likewise requires 
to be frequently filled, and as it empties, less water conies 
into contact with the stone, and therefore a smaller 
quantity, in such a state, can only pass through. Like- 
wise a filtering stone used in the common way soon be- 
comes useless, from the filth insinuating itself into the 
internal parts of the stone, out of the reach of the brush. 
In the method I propose and practise, the filtering- 
stone is placed within the water to be purified, which 
presses upon the outside of the filter, and the stone does 
not require to be supported in a frame as it needs only to 
stand within the water cistern ; it will thus filter, in an 
equal time, double the quantity of water procured in the 
common mode ; it fills itself, and requires no cleaning. I 
have upon this plan used one for more than three years 
with great success. I am, &c. 
April 18, 1810. William Moult. 
* Nicholson, vol. xxix, p. 324. From Trans, of the Soc. of Arts, vol. xxviii* 
p. 212. The silver medal was voted to Mr. Moult. 
