In the older type the combustion chamber (of metal or glass) is sunk in the calorimeter proper, tubes being provided for the entrance and exit of the gaseous substances involved in the action.
In the newer type (which was first proposed by Andrews for the combustion of gases) the chemical action takes place in a completely closed combustion chamber of sufficient strength to resist the pressure generated by the sudden action, which is often of explosive violence.
The steel combustion chamber is of about 250 c.c. capacity, and is wholly immersed in the calorimeter.
(a) The gas is made from the fuel in a detached fireplace and conducted while hot into the combustion chamber of the furnace, and the air for complete combustion is heated by the products of combustion on their way to the chimney.
The large combustion chamber B permits thorough combustion of the gas.