Dr. Lardner's Experiments on the Great Western Railway 408 Experiments on Resistance 409 Restrictions on Gradients 410 Compensating Effect of Gradients 412 Experiment with the "Hecla" 412 Disposition of Gradients should be uniform 415 Methods of surmounting steep Inclinations 415 CHAP. XII. LOCOMOTIVE ENGINES ON TURNPIKE ROADS. Railways and Stone Roads compared 420 Gurney's Steam Carriage 423 The Boiler of Gurney's Engine 423 His Method of cleansing Boilers 428 Convenience and Safety of Steam Carriages 432 Two Methods of applying Locomotive Engines upon common Roads 434 Horse Carriages compared with Steam 435 Extract from Mr. Farey's Evidence before the House of Commons 435 Hancock's Steam Carriage 436 How it differs from that of Mr. Gurney 437 Ogle's Locomotive Carriage 438 Dr. Church's Steam Engine 439 CHAP. XIII. STEAM NAVIGATION. Form and Arrangement of Marine Engines 441 Arrangement of the Engine-room 446 Marine Boilers 448 Effects of Sea Water in Boilers 450 Remedies for them 451 Blow-off Cocks 452 Indicators of Saltness 453 Seaward's Indicator 454 His Method of blowing out 454 Field's Brine Pumps 456 Tubular Condensers applied by Mr. Watt 457 Hall's Condensers 458 Substitution of Copper for Iron Boilers 460 Process of Stoking 462 Watt's Expedient of attaching Felt to the Boiler Surface 463 Means of economising Fuel 463 Number and Arrangement of Furnaces and Flues 463 Howard's Marine Engine 464 Application of the expansive Principle in Marine Engines 466 Recent Improvements of Messrs. Maudslay and Field 467 Humphrey's Marine Engine 470 Common Paddle-wheel 472 Feathering Paddles 474 Galloway's Patent for a Paddle-wheel with movable Paddles 476 Split Paddle 478 Proportion of Power to Tonnage 480