202 of superheated steam, an increase in the high-pressure cylinder diameter is not always advisable, and many times not possible. In such cases, if the same indicated horsepower is to be obtained, it is necessary to increase the cut-off in the high-pressure cylin- der, thus giving an increased volume of steam at cut-off, and, in effect, decreasing the cylinder ratio, If the volume at cut-off is not increased the indicated horsepower will be slightly decreased, assuming, of course, that the boiler pressure is not changed. The operation of engines using su- perheated steam is but very little dif- ferent from saturated steam operation. The two chief points under this topic are starting up and lubrication. In starting up, particularly with new en- gines, or if new liners or rings have been applied, nearly all superheater manufacturers recommend that sat- urated steam be used for a_ short time. After the engines are well heated, the mixing-pipe valve may be partly closed and the temperature of the steam in the high-presusre chest gradually raised. When the vessel is on a run, some hours should elapse before the full degree of superheat is used. The Problem of Lubrication Lubrication is probably the most prominent point in mind when first considering the use of superheated steam. In reality this need not cause apprehension. With low degrees of superheat, it is not always necessary to use any oil internally. This may be explained by the fact that the superheat is not sufficient to carry the steam through the high pressure cylinder without condensation. Where condensation occurs oil lubrication may not be necessary, and this is par- ticularly true when low pressures are carried. Low superheat really does little more than eliminate part of the initial condensation. With moderate degrees of superheat opinions differ as to the necessity for the use of oil. Cases are on record where a super- heat of more than 100 degrees has been successfully taken care of with- out internal oil lubrication. It seems probable, however, that in such cases heavy swabbing of rods was resorted to. When high degrees of superheat are considered, lubricating oil should certainly be applied internally. The quantity of oil needed to satisfactorily take care of 150 or more degrees of superheat is probably imagined as be- ing greater than what is actually re- quired. The average of a large num- ber of boats using high degrees of superheat shows that very favorable «results were obtained with about 0.3 THE MARINE REVIEW gallon of oil per 1,0U0 horsepower per 24 hours. The keynote of the lubrication question with highly su- perheated steam is that a regular sup- ply rather than a large quantity . of oil is required. The oil furnishes the lubrication previously afforded by the water present in the saturated steam, but it does not follow that a regular supply of oil means a large quantity of oil. Necessary Equipment Equipment to handle superheated steam, some of which may not be considered for saturated-steam installa- tion, is confined to lubricating-oil pump and pipes, filters, pyrometers, and mixing pipes for leading saturated steam to main steam pipe and super- heated steam to auxiliary steam pipe. An oil pump, driven from some con- venient part of the engine, is required to feed oil in a steady and regular manner. Inexpensive pumps are on the market,.and are reported as being reliable in service. Many of them are so arranged that the oil con- tainer is not under pressure, thus permitting a renewal of the. oil supply without trouble or danger. In mod- ern practice, the oil is introduced into the steam pipe between the throttle valve and the engine. The delivery end of the oil pipe fitting extends into the steam pipe, so that the cur- rent of steam entrains the’ oil and it is atomized before reaching the wear- ing parts. Filters are, of course, necessary where there is any possibility of oil being taken into the boilers. A large proportion of steamers using saturated steam in condensing engines are at present equipped with filters. It is believed that in a good many ships the filtering apparatus now installed, particularly with proper attention giv- en to cleaning, is adequate to pre- vent oil reaching the boilers. A num- ber of recently built ships, using high superheat, have had two filters ar- ranged in series, and reports from engineers on such boats indicate that oil does not get into the boilers so as to cause any damage. or give trouble. Pyrometers are desirable for mea- suring the temperature of the steam at various points. It appears, at the present time, common _ practice to have one pyrometer indicating the temperature of steam at the engine stop valve, also to have other py- rometers at points nearer the super- heater for indicating the temperature of the steam where it leaves the superheating apparatus. A pyrometer to register the temperature of steam in the intermediate-pressure chest is June, 191 also frequently applied. Various types of pyrometers which measure these temperatures accurately are available and are reliable instruments; the elec- tric pyrometer, especially, appears to have been developed in a satisfactory manner for marine practice. The in- formation given by the pyrometer is important, and makes it possible to determine how far superheat is being carried through the engine, and wheth- er any boiler is being properly or improperly fired. By showing a re- duction in steam temperature, the pyrometer gives warning of an im- pending fall in boiler pressure; in other words, it acts as a danger sig- nal as regards pressures. A small diameter mixing pipe is generally provided, so that saturated steam can be taken from the boiler directly to the main steam pipe lead- ing to the engines. The use of this pipe has been criticized in some quar- ters on the ground that the propor- tion of steam flowing through the pipe, if adjusted for a certain condi- tion of maximum load, will, at other loads, permit a different quantity of steam to flow through the pipe, and the temperature of the engines will fluctuate. It is further contended that at ‘light loads too much steam. will pass through the mixing pipe, having a tendency to short circuit the super- heater, in which case the superheater pipes may become overheated. Economy of Superheat Auxiliary machinery may be more economically operated when super- heated steam is available. Pipes for accomplishing this may be arranged so that the desired amount of super- heated steam can be led to the auxil- iary steam line, the quantity depend- ing on the kind of machines to be operated, the distance of these ma- chines from the mixing pipe, and the severity of weather. If auxiliary ma- chinery is fitted for the full degree of superheat obtainable, maximum economies are, of course, possible. If the machines are not arranged for superheated steam, there is still op- portunity of effecting considerable saving by feeding enough high-temper- ature steam into the auxiliary line, to carry practically dry or even slightly superheated steam up to the auxiliary engines. With long pipe lines lead- ing, for instance, to steam winches operating in cold winter weather, the economy in steam which is obtain- able will be very readily appreciated. Winches thus provided will use steam instead of a very high proportion of hot water. In fact, the percentage of economy, by using thoroughly dry steam, in auxiliary machinery will