June 20.] THE NEW ZEALAND GAZETTE. 1885

they be shut? Neglect of these cocks leads to what dangers?

48. Scale: Of what does it consist? Where is it most objectionable? How is it removed? How is its formation prevented? What evil effects are produced by it?

49. What is a salinometer? Of what does it consist? How does it act? How is it graduated? Can it be used at any temperature indiscriminately?

50. What harm may be done through the check-valve of one of a set of boilers being defective while under way? How would you work to avoid this harm?

51. How is the leak from a split tube stopped in a boiler at sea? Describe the operation.

52. What is the use of dampers? Where are they fitted? When should they be used?

53. When there are no dampers fitted, what is used instead? What evil to the boiler is sometimes attributed to this? When the heating-surfaces are clean, does this occur?

54. Describe the piston of a steam-cylinder with its different rings and their uses? There are generally round pieces let in flush on one side of a piston: what are they? How are these pieces fixed?

55. Cylinder drain-cocks: what is their use? There is sometimes a valve upon each cock: what purpose does it serve?

56. Cylinder escape-valves: Of what do they consist? How protected? How regulated? When are they most needed? To what danger do they expose the engineer? What precaution is sometimes used to obviate this danger?

57. What is a compound engine? What different kinds are there for screw-steamers in respect to the number and arrangements of their cranks and cylinders? What is a triple-expansion engine?

58. What is link-motion? What are some of its advantages? In modern engines for the screw propeller, when there is no link-motion, what takes its place?

59. What is a separate expansion-valve? Why is it not fitted to all engines? What effect has an expansion-valve upon the starting and upon the reversing of the engine?

60. What arrangement is applied to reduce the friction of a slide-valve? To what is the friction due?

61. Describe a loose eccentric. How does it act? In what engines are the loose eccentrics still employed?

62. What is the travel of the eccentric rod? How is it measured on the eccentric? What is the travel of the slide-valve when the link-motion is in mid-gear, and the engine still moving?

63. What are “double-beat valves”? What objections are there to their use?

64. What is a circulating-pump? Is it always worked by the main engine? Give an example from your last steamer of the three water-temperatures generally noted by careful engineers?

65. An air-valve is sometimes fitted to a circulating reciprocating pump: what purpose does it serve?

66. What is the difference between a bucket air-pump, a piston air-pump, and a plunger air-pump?

67. Whether are double-acting air-pumps made with plungers, with pistons, or with buckets? Circulating-pumps: describe their construction and action.

68. What is an air-pump trunk? When is it necessary? How is it attached to the bucket? Centrifugal pumps: describe their construction and mode of working.

69. What class of air-pump requires both foot and delivery valves, and in what other class can either of these valves be in some cases dispensed with?

70. What are marine governors? What is their general construction? How do they act?

71. With a surface condenser and a single-acting air-pump, what is the effect of a leaky foot-valve; and what is the effect of a leaky bucket when there is also a foot-valve?

72. Air-pump pet cock or valve: Where is it placed? How does it act? What is its object? Does it in every case reduce the effective capacity of the pump? Is it equally applicable to double-acting pumps?

73. At what temperature is the hot well worked? What is the effect of higher temperatures? What is the effect of lower temperatures? What limits the lowness of temperature? Has a very low temperature any disadvantages?

74. Bilge-injection with common condensers: What are the fittings required? When is it used? What precautions are necessary in using it?

75. When surface condensers are used, what takes the place of the bilge-injection? To what is the connection made? How is its valve formed? Why is this necessary?

76. What are the practical guides to the proper amount of opening of the inlet-valve for the circulating-pump?

77. Feed-pump pet cock or valve: Where is it placed? What is its use? How does it act? Is it always a necessary fitting?

78. What are some of the ways of fastening the ends of surface-condenser tubes? About what size and about what thickness are condenser-tubes? What parts of a surface condenser are made of brass?

79. What is a blow-through valve or cock? To what is it attached? There is sometimes a valve that when opened admits steam from the slide-valve casing to the exhaust port: What is its use? To which cylinder is it fitted?

80. What are snifting-valves? Why are they generally omitted now?

81. What connections are generally fitted to the donkey-pump, and to what services can it be applied?

82. When the engines are stopped with steam up, what are to be shut and what are to be opened?

83. How is an engine heated up before starting? What precautionary examinations are made before starting?

84. What is an interceptor or catch-water? Where is it fixed, what is its construction, how does it act, and what attention does it require?

85. Describe an air-pump bucket with its valve or valves and its packing. Of what are the valves generally made?

86. Of what materials are air-pump rods made? Why so?

87. What is the racing of the engine? When does it occur? What danger attaches to it? What is done to prevent it?

88. When under way, when the air-pump bucket is at the top of its stroke, at what height is the water in the condenser?

89. What is meant by the “pitch” of a screw propeller? How is it measured?

90. Explain the difference between a “right-hand” and a “left-hand” propeller, and state how each of them revolves.

91. What is the slip of a screw propeller? How is its amount expressed in figures?

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