1 16 New Method of applying the Filtering Stone. 



Thus then, it appears, sir. that Dr. Masktlyne never de- 

 termined the njeau density of the tarih: ihai Mr Caven- 

 dish's late attempt can be considered onlv as a pretty and 

 amusing little exjieriment, tending to corroborate the result 

 of the calculations made on the large exi)criment; by, sir. 

 Your obliged himible servant, 



Charles Hutton. 



London, August 14, 1811. 



XXVr, Description of a neiv IMethod of applying the Fil- 

 tering Stone for purifying Water, By Mr. William 

 Moult*. 



Sir, If you think the following information, relative to a 

 new methodof filtering water, is deserving of the attention of 

 the Society of Arts, &c. I wish you would lay it before them. 

 My objections to the old method of filtering by jnitting wa- 

 ter into the filtering-stone are, that the dirt falls to the bot- 

 tom, 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 comes in contact with the stone, 

 and therefore a smaller quantity only, in such a state, can 

 pass through. Likewise a filtering-stone used in the ■com- 

 mon way soon becomes 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 onlv to stand within the 

 water cistern ; it will thus filter, in an equal time, double 

 the quantiiy 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, sir. 



Your humble servant, 



No. 37, Bedford-square, April 18, 1810. VVlLLIAM MoULT. 



To C. Taylor, M.D. Sec. 



• From Trannacllons of the Society for the Encouragement of Arts, Mannfac- 



tares, and Contmerce, for 1810. The Society voted their silver medal to 



Mr. William Mf/ult for this communication. 



Re. 



