Whilst passing through this apparatus, the air is deprived of 

 all traces of ammoniacal vapour, and is afterwards conducted into 

 a chimney, which conveys it away. 



The contents of the purifj/ing chamber, when fully saturated 

 with ammoniacal salts, are removed and sold as manure or other- 

 wise applied to some useful purpose ; fresh charcoal is then 

 placed in their stead. When several precipitations have been 

 effected, and it becomes necessary to remove the deposit that has 

 accumulated in the tank, a valve at the lower part of the vessel 

 (and to which the bottom inclines) is lifted up, and the semi- 

 fluid mass contained in the cistern is allowed to flow off into a 

 trough placed beneath, whence it is transferred to a series of 

 endless linen bands, revolving in a hot-air chamber. By these 

 means the manure is soon rendered perfectly dry, and is then fit 

 for the market. When the quantity of manure manufactured is 

 limited, and labour is of little or no object, it has been found 

 preferable to mould the deposit by hand, and stove-dry it. The 

 latter method, I believe, is at present pursued at the Cardiff Gaol. 



The water that runs off from the deposit in the tanks is almost 

 wholly inodorous, perfectly clear and limpid ; and, if first passed 

 through a filter of animal charcoal, might even be made use of 

 for drinking, although a natural prejudice would of course prevent 

 it from being so employed. 



It might, however, be well rendered available for the irrigation 

 of land in those places where the level would admit of its being 

 economically distributed. Indeed, the small quantity of alkaline 



