_Motive Power._--The paper-maker has taken advantage of every modern improvement in steam engines for the purpose of reducing the cost of motive power. Amongst other alterations in this direction the use of a high speed enclosed engine and the employment of the modern steam turbine may be noted. In the enclosed engine the working parts are boxed in by a casing fitted with oil-tight doors. The cranks and connecting rods splash into the oil, which is thus thrown about in all directions, so as to ensure sufficient lubrication. Another feature of this engine is the variable speed, and it is possible to run the paper machine at speeds varying from 100 to 500 ft. per minute without the use of change wheels. _Electrical Driving._--The application of electricity for motive power has made steady advances in the paper mill. At first it was limited to the driving of machinery in which variations of speed or load were not required to any large extent, but of recent years beating engines, calenders, and paper machines have all been fitted with electrical drives. [Illustration: FIG. 56.--An "enclosed" Steam Engine.] The following details relate to the installation at the Linwood Paper Mills:-- The installation consists of 250-K.W. steam dynamos. The engines are Willan's high speed triple expansion, working with a boiler pressure of 250 lbs. per square inch at the stop valve, the steam being superheated to give a temperature of 500° Fahr. at the engine. By means of jet condensers a vacuum of 25 to 25½ inches is obtained on the engines. The two boilers are of the Babcock type, and have 3,580 square feet of heating surface each. The furnaces have chain grate stokers, and the boilers are arranged with their own superheaters. The motor equipment consists of eight 80, two 50, and ten 25 B.H.P. motors. Six of the 80 B.H.P. drive the beating engines, and it has been found that the motors readily respond to an overload of 50 per cent. without beating or other trouble. To remedy the excessive and sudden variation a belt drive was adopted. An 80 motor drives the pulp refining engine. The two paper-making machines have each two motors, one a 25 and a 50 and the other two 25 B.H.P. motors. The speed can be regulated with exactitude. The auxiliary plant of the paper-making machine, pumps, agitators, etc., is worked from lines of shafting driven by motors. Calender motors are of the variable speed type, being designed to run from 100 revolutions per minute to 600 revolutions per minute. Variations from 300 to 600 revolutions per minute can be regulated by the shunts, the loss being negligible. Several of the motors are geared up to the various machines, as is the case with the calender. As regards cost, the capital outlay on the 500-K.W. generating plant, including engines, dynamos, boilers, condensers, steam pipes, filters, etc., and all engine room accessories, was £9,500. [Illustration: FIG. 57.--An Electrically Driven Paper Machine.]