Of the Use of Steam. 325 



is to heat ; otherwise this liquid will be in danger of 

 being forced back by this opening into the steam-boiler : 

 for, as the hot steam is suddenly condensed on coming 

 into contact with the cold liquid, a vacuum is necessarily 

 formed in the end of the tube ; into which vacuum the 

 liquid in the vessel, pressed by the whole weight of 

 the incumbent atmosphere, will rush with great force 

 and with a loud noise ; but if this tube be placed in a 

 vertical position, and if it be made to rise to the height 

 of six or seven feet above the level of the surface of the 

 liquid which is to be heated, the portion of the liquid 

 which is thus forced into the lower end of the tube will 

 not have time to rise to that height before it will be met 

 by steam, and obliged to return back into the vessel. 



There will be no difficulty in arranging the apparatus 

 in such a manner as effectually to prevent the liquid to 

 be heated from being forced backwards into the steam- 

 boiler ; and when this is done, and some other neces- 

 sary precautions to prevent accidents are taken, steam 

 may be employed, with great advantage, for heating 

 liquids, and for keeping them hot in a variety of cases 

 in which fire, applied immediately to the bottoms of the 

 containing vessels, is now used. 



In dyeing, for instance, in bleaching, and in brewing, 

 and in the processes of many other arts and manufac- 

 tures, the adoption of this method of applying heat 

 would be attended not only with a great saving of 

 labour and of fuel, but also of a considerable saving 

 of expense in the purchase and repairs of boilers, and 

 of other expensive machinery : for, when steam is used 

 instead *of fire, for heating their contents, boilers may 

 be made extremely thin and light ; and as they may 

 easily be supported and strengthened by hoops and 



