116 



MANUFACTURE OF SUGAR. 



selected, whether the heat be applied to them by the 

 furnace, or bv high pressure steam. As soon as the 

 syrup has attained a density ranging from 27° to 32° 

 Beaume, according as it is to be again filtered or not, at 

 which latter density it will have reached a temperatm'e of 

 about 220° F., it must be drawn off into a cistern or other 

 convenient receiver, that the concentration may be finished 

 at a lower temperature. A variety of plans have been 

 tried to effect the rapid concentration of syrups at a 

 low temperature, but the most perfect is by the vacuum 

 pan, in which the concentration is finished, without injury, 

 at a temperature of 160° to 180° F., and sometimes much 

 lower. The high price of this apparatus has caused 

 many contrivances to be made for effecting the object in a 

 less costly manner. Some of these require a steam engine 

 to work them, but in these the difference in cost not 

 being very great, it would be far preferable to have the 

 vacuum pan at once. Others are of a very simple and 

 economical description \ and of these the most useful is the 

 vessel known latterly as Gaddesden's pan, although I 

 believe it had been used in the French Colonies both in 

 the East and West Indies, for many years before Mr. 

 Gaddesden brought it to the notice of the public. Dr. 

 Evans describes it as follows : — " This gentleman's appara- 

 tus consists of an iron or copper pan, having nearly the 

 form of the half of a hollow cylinder, in which is placed a 

 drum or wheel, adapted to the shape of the vessel, and 

 formed of a number of metal rods so arranged that the 



