NECESSITY OP RAPID EVAPORATION. 



115 



left in the back of the boiling-house for the escape of the 

 steam. This is called a chimney of aspiration, and is an 

 effective method of sending a current of air across the sur- 

 face of the boiling liquid, sufficient to carry off the steam 

 as fast as it appears, when, as is usual in the lesser Antilles, 

 the evaporating vessels are erected on the lee-side of the 

 building, through which a current of air generally passes. 

 Whenever this method cannot be rendered effectual, it 

 would be advantageous to produce an artificial current of 

 air, by means of an insufflator, or any other available 

 method, as this would hasten evaporation, and economize 

 fuel to a great extent. For the process of evaporation, if 

 the vessels are of the proper form, the direct heat of the 

 furnace is as effective as that of steam, the only advantage 

 which the latter possesses in any part of the operation, 

 being the ease with which the degree of heat can be 

 regulated. Many planters imagine, that syrup does not 

 become caramelised if concentrated in a steam tavche ; but 

 this is quite a chimera, the degree of heat and suscepti- 

 bility of injury therefrom being in both cases alike. 



The advantage which steam possesses in this, as in every 

 other part of the process, consists in the ease and readiness 

 with which it can be managed, any degree of heat as may 

 be found requisite being easily applied, and the instant 

 cessation of its action at command, when no longer 

 required. The most important object to be attained in 

 the process of evaporation is rapidity ; and the vessels best 

 adapted to accomplish this end are to be judiciously 



