Fig. 2. KOUM AND POSITION OF THE SCREW. 



STEAM NAVIGATION. 

 CHAPTER II. 



28. Arrangement of the engine-room ; governor and other regulating parts 

 omitted. 29. Flue boilers and tubular boilers. 30. Construction of 

 flue boilers. 31. Tubular boilers. 32. Indications of engineering 

 ignorance. 33. Number and dimensions of tubes. 34. Incrustation 

 produced by sea water. 35. Hydrometric indicators. 37. Thermo- 

 metric indicators. 38. Seaward's contrivance. 39. Brine-pumps. 

 40. Blowing out. 41. To detach the scale. 42. Effect of corrosion. 

 43. Efficiency and economy of fuel. 44. Coating the boiler and 

 pipes with felt. 



28. The general arrangement of the engine-room of a steam- 

 vessel is represented in fig. 3, page 131. 



The nature of the eftect required to he produced hy marine 

 engines, does not render either necessary or possible that great 

 regularity of action, which is indispensable in a steam-engine 

 applied to the purposes of manufacture. The agitation of the 

 surface of the sea will cause the immersion of the paddle-wheels 

 to be subject to great variation, and the resistance produced by 

 the water to the engine will undergo a corresponding change. 

 The governor, therefore, and other parts of the apparatus, con- 

 trived for giving to the engine that great regularity required in 

 manufactures, are omitted in nautical engines, and nothing is 

 introduced save what is necessary to maintain the machine in its 

 full working efficiency. 



Marine boilers are constructed in forms so infinitely various, 

 that, in a notice so brief and popular as the present, we can only 

 indicate some of their more general arrangements, and aid the 



LARDNER'S MUSEUM OP SCIENCE. K 129 



No. 122. 



