THE object of the writer's present paper is to give a brief resum of what takes place in a condenser, and particularly to discuss some points which are important for getting the best result out of condensing plants. The paper is limited to the condenser proper and the pumps. In almost every case the condensing is done by the cooling action of water, while the air, which enters the condenser in different ways, and which would destroy the vacuum, is pumped out, either separately or together with the water. The prevailing custom is to measure the low pressures created in the condenser by comparing them with the average barometer ; but, as the barometer varies in different places, and in one place at different times, this method does not show what a condenser does, while it also is likely to lead to mistakes ; for instance, a Rand engineer, who has gone to much trouble in studying condensation problems, stated some years ago that turbines would not be a success on the Rand, the altitude there being too great to allow of the high vacuum which a turbine needs for a low steam consumption. Now, an engine will give the same results, other conditions being equal, with the same absolute pressure in the condenser, no matter what the vacuum is. It is therefore useless to ask the maker of a steam engine or turbine to guarantee a certain steam consumption at a certain vacuum. The difference in Broken Hill, where the average barometer is 28r, compared with 30" at sea level, may be very much to the advantage of the engine-maker.