C V Boys' gas calorimeter, late 19th century.

Sir Charles Vernon Boys (1855-1944) was an English physicist who designed this piece of apparatus. A calorimeter can be used to discover the calorific value of a given fuel. A steady supply of gas is burned inside, and this heats a steady supply of water. By measuring the temperature rise, the calorific value of the burning gas can be calculated. From the late 19th century gas was used for both domestic heating and lighting. This device was used to charge customers the calorific value of the gas they had consumed.