RAILWAYS 



555 



for economy of fuel is the adaptation to the loco- I doing duty in one cylinder or pair of cylinders is 



motive of the ' compounding ' principle which has 

 effected such a revolution in steam navigation. By 

 this invention (see STEAM-ENGINE ) the steam after 



made available through its expansive power in 

 another and larger cylinder. Engines formed on 

 this plan are used extensively on the London and 



Fig. 3. Compound Express Passenger-engine, North-Eastern Railway. 



North- Western Railway, the North -Eastern, ami 

 the Great Eastern. A saving of from 10 to 15 per 

 cent, in fuel is claimed by advocates of compound 

 locomotives, the objection being a complication of 

 parts. 



Considerable diversity has hitherto existed in 

 the type of locomotive on various lines ; but the 

 policy now adopted by nearly all the leading com- 

 panies of manufacturing their own rolling-stock, 

 and the obvious advantage of having interchange- 

 able parts, has led of late to the gradual adoption 



of a more uniform style of construction for the 

 different kinds of service required. As a general 

 rule inside cylinders are in use on the through 

 lines of the United Kingdom, it being contended 

 by many authorities that for high speeds the 

 placing of the weightier parts of the machine close 

 to the centre of gravity minimises oscillation. It 

 is held further that the moving part of the 

 machinery is better protected by being placed 

 within the wheels. On the other hand, the 

 objections to be urged are the increased cost and 



Fig. 4. Typical American Engine. 

 (From "The Railways of America.") 



complication of the driving-axle and the compara- 

 tive inaccessibility of the valves and pistons for 

 purposes of repair. Outside cylinders have been 

 adopted on the London and Soutli-Western Railway 

 and on other lines ; and, supported by the 

 bogie-truck, this form of engine approxi- 

 mate* closely to the type in use on 

 American railroads. The bogie-truck con- 

 sists of a separate frame carried by two or 

 more Bete of wheels anil attached to the 

 engine or carriage by a central pivot ; by 

 this contrivance the wheels adapt them- 

 selves more readily to ineqoalitiei or to 

 sharp curves. The lxiler on English loco- 

 motives is invariably carried on a stiff plate 

 frame, while in the comparatively cheaper 

 form in use in the United States the 

 running portion of the machinery is at- 

 tached directly to the boiler by means of 

 a bar frame, which in Britain is thought 

 to throw undue strain upon the structure. 

 Be that as it may, the types of passenger 

 express engines in England and in the United 

 States are undoubtedly approximating more and 

 mure closely (see fig. 4'). The large nogle-drivin 

 wheel at one time generally used on express loco 



motives is now more rare, except in the case of 

 some of the new compound engines, but for high 

 s|>eeds it possesses some advantages. For goods- 

 engines the six-coupled wheel, inside cylinder type, 



Fig. 5. Six-coupled Goods-engine, 1.. <V- V. Railway. 



is in most general use, while the forms of tank- 

 engines for local and suburban lines and for shunt- 

 ving ing purposes vary with the different companies and 

 loco- tliu different services to be performec'.. Of acct-s- 



