In this receptacle he directs the air to be heated , by the application of heat externally to the receptacle .
Thus he accomplishes the object of applying the blast , which before was of cold air , in a heated state to the furnace .
In this receptacle he directs the air to be heated , by the application of heat externally to the receptacle , and thus he accomplishes the object of applying the blast , which before was of cold air , in a heated state to the furnace .