166 THE COMMON METHOD BY HEAT. 
clined plane is broad. The space between these strips 
forms a continuous channel through which the juice flows 
alternately in opposite directions, and thus passes slowly 
over the whole surface before it arrives at the bottom.” 
It would be difficult to describe more accurately and 
minutely in its essential features the sorghum evaporator 
before mentioned, but from the connection in which the 
description of this one is found, it is evident that it was 
proposed to limit its use to the evaporation of previously 
defecated solutions, and therefore that it was not open to 
the objection above alludedto. Derosne’s pan was heated 
by steam, but this form of surface was not found to possess 
any peculiar advantages, nor can any such be justly claimed 
for it now in its present resuscitated form. 
It is noteworthy, also, that those who advocate the use 
of heat, unassisted even by lime, thereby limit its action 
to a very small share of the influence of which otherwise 
it is really capable. Fresh cane juice is always more or 
less acid, and when in this condition its temperature is 
raised to the boiling point, and it is afterward allowed to 
remain at rest for a short time, a scum separates, in which 
may be detected more or less albumen, green coloring mat- 
ter, ete. The liquid underneath is still more or less turbid, 
and of a greenish-yellow tinge. The action of heat is con- 
fined to the coagulation of only a portion of the albumin- 
ous matter, the remainder is held in solution by means of 
the acid, a boiling heat has no further effect upon it, and it 
passes into thesyrup. The greenish tinge so common in 
all the light-colored acid syrups is the best evidence of the 
presence in it also of incoagulable albuminous matter and 
gum, which hold a portion of the coloring matter suspended 
in the solution. The consequences of this practice are 
hurtful to both the sugar and syrup by 1. The production 
of an acid syrup. 2. The destruction of a part of the 
