Abstract: An apparatus for transferring liquid between regions of a first and a second pressure comprising:a vessel,a dividing member in the vessel, the vessel and the dividing member being relatively movable to divide the vessel into separate variable volume chambers,a first pair of valves,one of which controls passage of liquid between a first of said chambers and said region of a first pressure,the other of which controls passage of liquid between a second of said chambers and said region of a first pressure,a second pair of valves, one of which controls passage of liquid between said first chamber and said region of a second pressure,the other of which controls passage of liquid between said second chamber and said region of a second pressure,operating means repeatedly to perform the following cycle of operations;close the valves of one of said pairs and open the valves of the other of said pairs,then move the dividing member to cause the volume of said first chamber to increase and the volume of said second chambe

Abstract: A method of operating an internal combustion engine in which there is introduced into a combustion chamber, inert carrier gas, combustion supporting gas and fuel, the fuel is caused to combust in the combustion chamber and exhaust gas is exhausted from the combustion chamber wherein the carrier gas comprises a significant proportion of carbon dioxide and the exhaust gas is treated with water to remove from the exhaust gas and absorb in the water an amount of carbon dioxide generally equal to the quantity of carbon dioxide added by said combustion, and the thus treated exhaust gas is returned to the combustion chamber to provide the carrier gas. The carrier gas may have inert gas such as argon added thereto in proportions controlled such that the gamma value of the mixture of gases equals a predetermined value which may be approximately that of air.