110 



MANUFACTURE OF SUGAR. 



inches square, which is placed beneath the delivering cock, 

 to prevent the washing away of the charcoal. In niters of 

 the size described, the depth of syrup above the superior 

 metallic plate, should be regulated at four inches. This has 

 been decided by practice, as the most suitable depth, and 

 can easily be regulated by a float-cock. A greater depth 

 in these small vessels is found to create what are called 

 false-channels, through which the syrup runs without filtra- 

 tion. On leaving the filters the syrup is colourless. 

 Whenever it retains a portion of colour, the charcoal is then 

 considered as exhausted for the time, and must be renewed. 

 The process of revivifying charcoal, by which its decoiourat- 

 ing power is restored, consists simply in washing and 

 burning in suitable vessels. * * * Eight filters such 

 as have been described, and lined with zinc, may be pur- 

 chased in Havre for £16 sterling. They are sufficient for 

 a boiling house making from 3 to 4 tons per day. Two are 

 recharged daily." Peyron's filters are thus described by 

 Dr. Evans : — " These filters are composed of a series of 

 cylindrical copper vessels, each having a double bottom as 

 those of Dumont, and being hermetically closed at the top. 

 They are closely packed with animal charcoal j and into 

 the upper part of the first vessel is introduced a pipe for 

 the admission of the syrup, which is made to descend from 

 a sufficient height, or which is forced in by means of a 

 pump, in such a manner, that from the pressure employed, 

 it passes rapidly through the charcoal, and is received by 

 the space between the two bottoms. Here it enters another 



