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The Friction of Locomotive Slide-Valves." Ry JOHS AUDLEY FREDERICK ASPISALL, M. Inst. C.E. THE attention of the Author has been drawn to the fact that few, if any, trustworthy data exist of the friction of slide-valves under steam. Hence he was led to make experiments on locomotives, with a view of ascertaining whether the amount of slide-valve friction was as great as it is commonly assumed to be. The only previous investigations of the friction of slide-valves with which the Author is acquainted are as follow :-In 1866, a Paper by Mr. Thomas Ada'ms, " On the Friction of the Slide-Valve and its Appendages," read at the Society of Engineers.l I n 1871, a Paper by Mr. W. G. Beattie, "Description of a Balenced Slide-Valve for Locomotive-Engines," was read at a meeting of the Institution of Mechanical Engineers.2 Both these Papers were intended to show the superiorit,y of balanced valves over the ordinary valve. But the Author is not aware that either form of balanced valve is now in use, as the mechanical difficulty of keeping them in order outweighs their other advantages. Mr. Beattie states that a valve 104 inches long

ENGINEERINGt CONFERENCE. [Conference surface was required. (4) Various methods of cooling condensing water were in vogue, such as spraying it in an artificial current of air, or trickling it over surfaces in thin films. No. 3.