Practical instructor and reference book for locomotive firemen and engineers: a practical treatise ...

Front matter

Class _1 __ 2

Book

GopightN -

Introduction

Realizing that the Locomotive Engineer who is all practical without any technical knowledge of the construction and operation of the Locomotive is giving way to those who are more progressive, and who are ambitious enough to want to know the why and wherefore, the cause as well as the effect of the action of the different parts of the Locomotive;

Therefore in writing this Book the Author has endeavored to combine technical knowledge with practical experience in such a way that anyone may thoroughly understand the explanations given, describing the different parts in a manner which will be appreciated by the Fireman student or Engineer who desires a practical book of reference.

In writing this Book the Author has made use of the knowledge gained by practical experience as well as technical research, combining the practical knowledge gained by years of experience in the Locomotive Shops and on the Road as a Fireman and Engineer with the technical knowledge gained by a careful study of construction and operation.

Hoping that this book may prove to be the key which will unlock the door to a successful future for many an

6 INTRODUCTION

aspiring and ambitious Fireman and Engineer, I am yours in the interest of my fellow men and the elevation of the standard of our calling.

THE AUTHOR.

I take this opportunity of extending appreciation and thanks to my many friends who have helped to make my first book, Instructions for Locomotive Firemen, a success.

Hoping that this Book (Instructions for Locomotive Firemen and Engineers) will receive as kindly a reception as my first effort,

Preface

Instructions for Locomotive Firemen and Engineers is written for the purpose of giving the fireman that practical working information which is necessary to his success and to help him to advance himself to the highest point of efficiency as a fireman and then assist him to gain a practical working knowledge of the Locomotive that will enable him not only to pass a successful examination but to become a successful engineer as well.

For the convenience of the student in the study of this book, it has been divided into six parts, each part being complete in itself.

Part One

The Fireman's Duties — How to Fill the Lubricator and Other Duties — Color Signals — Hand, Flag, and Lamp Signals — Engine Steam Whistle Signals — Air Whistle Signals Used in Passenger Service — Combustion — The Atmosphere — Definitions — The Process of Combustion in Detail — Methods of Firing — The Bank Fire — The Graduated Fire — The Level Fire — Addenda to Part One 1 7-34

Part Two

General Description of the Locomotive, Its Construction and Operation — The Boiler — Names of the Different Parts of the Boiler — The Engines — Reciprocating and Circular Motion — The Pistons — Cross-Heads and Guides — Main Rods — Parallel Rods ; — The Driving Wheels — The Crank-Pins — The Driving Axles — Locomotive Frames — Driving Boxes — The Spring Saddle — The Driving Springs — Spring Hangers — Equalizers — Engine Trucks— The Valves— The Slide Valve— The Allen Valve— The Piston Valve — Lap — Lead — Valve Gears — The Stephenson Valve Gear— The Link Block— The Saddle Pin— The Slide Valve Operated by The Stephenson Valve Gear — The Allen Valve Gear — The Walschaert Valve Gear — Direct and Indirect Motion of The Walschaert Valve Gear — Relative Positions of The Valve, Main Pin, and Eccentric of The Walschaert Valve Gear With Inside Admission Valve — Valve Setting — Injectors — To Operate the Injector — Injector Defects — To L^se the Injector as a Heater — Injectors Leaking Steam at Overflow — To Test for Leaks in the Supply Pipe — Names of Different Parts of the Lubricator — Lubricator Defects and Remedies — The McCord Force Feed Lubricator — Explanation of Operation — Operation 9

10 CONTENTS

of the Transformer — The Transformer — The Steam Gauge- Gauge Cocks — The Whistle and Bell — The Water Supply — Water Foaming — The Cause of Foaming and its Remedies — Running with Bad Water — Priming — Steam — Superheated Steam — How Steam Passes through the Engine and Operates it — Names of Principal Parts of the Locomotive 35-122

Part Three

Locomotive Breakdowns and their Remedies — Front Cylinder Head — Back Cylinder Head — Cross-Head — Main Rod — Side Rods — Main Pin — Front, Back, or Intermediate Pins — Main Axle — Front Axle — Intermediate Axle — Rear Axle — Broken Tire — To Remove Front Side Rod Connection — To Remove the Valve Stem Pin from the Rocker Arm — Broken Valve Yoke — Main Steam Valve, Steam Pipe, or Steam Chest — Broken Eccentric Strap or Rod, Broken Spring, Spring Hanger, or Equalizer — Broken Reverse Lever, Reach Rod, Link Hanger, or Tumbling Shaft — Breakdowns of The Walschaert Valve Gear — Broken Eccentric Rod — Broken Eccentric Crank or Link Extension — Broken Lift Shaft or Radius Rod Hanger — Broken Radius Rod — Broken Cross-Head Arm — Broken Combination Lever — Broken Cross-Head — Testing for Blows — To Test the Cylinder Packing — Pounds — How Located — Driving Box Adjustment — Driving Box Wedges — To Throttle Valve Cocked or Disconnected — Sand and Its Use — The Mallet Articulating Compound Locomotive, General Construction — General Dimensions of the Double Consolidated Mallet Type Locomotive, Class E-3.

123-155 PART FOUR

Air Brakes — The Westinghouse Air Brake System — The Westinghouse Nine-and-a-Half-Inch Air Pump — Westinghouse Eightand-a-Half-Inch Cross Compound Compressor — The Steam End — Air Pump Governors — The S F Air Pump Governor — Engineer's Brake Valves — The Combined Automatic . and Straight Air Brake — Automatic Brake Valves — The G-6 Type of Engineer's Brake Valve — Running Position G-6 Type — Service Application Position G-6 Type — Lap Positions — G-6

CONTEXTS 11

Type — Emergency Position G-6 Type — The E T Locomotive Brake Equipment — Piping of the E T Xo. 6 Equipment — The Dead Engine Feature — The Distributing Valve and Double Chamber Reservoir — Explanation of Diagrammatic Mews of the Distributing Valve — Distributing Valve, Automatic Operation of Charging Position — Distributing Valve, Automatic Service — Distributing Valve, Service Lap, Distributing Valve, Automatic Release — Distributing Valve, Emergency — Distributing Valve, Emergency Lap — Distributing Valve, Independent Brake, Operation of — Distributing Valve, Independent Release — Distributing Valve, Quick Action Cylinder Cap — Emergency Position of Distributing Valve with Quick Action Cylinder Cap — The H-6 Engineer's Brake Valve — Rotary Valve, H-6 Automatic Brake Valve — Charging and Release Position, H-6 Type — Running Position, H-6 Type — Service Position, H-6 Type — Lap Position, H-6 Type — Holding Position, H-6 Type, Emergency Position, H-6 Type — -The S-6 Independent Brake Valve — Running Position, S-6 Type — Slow Application Position, S-6 Type — Quick Application Position, S-6 Type — Lap Position, S-6 Type — Release Position, S-6 Type — B-6 Feed Valve — Double-Heading — Triple Valves — Quick Action Triple Valve — Charging Position — Service Position — Lap Position — Release Position — Emergency Position — The K-2 Triple Valve — The .Air Signal System — The Air Whistle Signal Valve — Pressure Retaining Valves — Testing Train Brakes — Applying the Brakes — Facts to be Remembered in the Operation of the Automatic Brake System — Releasing the Brakes — Disorders of the Air Brake Equipment and their Remedies 156-274

Part Five

Extract from Standard Rules — General Definitions — Signal Definitions — Interlocking Signals — The Time Table — Train Protection — The Locomotive Engineer — Economical Operation — Personal Injuries — Deportment 275-286

PART SIX Questions for Examination 287 ILLUSTRATIONS

PAGE

Air Compressor, 8J-Inch Cross Compound, Up Stroke . .165 Air Compressor, 8J-Inch Cross Compound, Down Stroke . 166 Air Pump, 9J-Inch, Showing Reversing Valve . . . .160 Air Pump, 9 J-Inch, Showing Main Valve . . . . .162

Air Pump, Governor, The S-F-4 .169

Air Whistle Signal Valve . . . . . . . .262

Allen Valve Gear . . . . .. . . . -7°

Angularity of Main Rod ........ 45

Automatic Reducing Valve -185

Automatic Brake Valve G-6, Release Position . . . . 179

Service Application Position . . . . . .182

Automatic Brake Valve, H-6 225

Removed from its Pipe Bracket .226

Rotary Valve 228

Rotary Valve Seat .229

Sectional View, No. 1 . . 227

Sectional View, No. 2 230

Boiler Check Valve . . . . . . . -93

Choke Valve 101

Choke Valve, Sectional View . . . . . . . 101

Combined x\ir Strainer and Check Valve ..... 193

Detroit Lubricator, Front View 94

Front Sectional View . . . . . . . -97

Side Sectional View 98

Sight Feed Glass and Fittings for Detroit Lubricator . . 96 Distributing Valve and Double Chamber Reservoir . . . 195

Instruction Diagram 189

Piping Diagram 188

14 ILLUSTRATIONS

Distributing Valve and Double Chamber Reservoir page

Diagrammatic View of . . . . . . . . 199

Pipe Connections . . . . . . . . .196

Distributing Valve . 200

Automatic Service ........ 205

Emergency Lap . . . . . . . . .214

Emergency Position with Quick Action Cap . . -223 Graduating Valve, Equalizing Valve and Seat . . .201 Independent Application . . . . . . .216

Independent Lap . . . . . . . . .217

Independent Release after an Automatic Application . .219 Quick Action Cylinder Cap for No. 6 Distributing Valve . 220 Release, Automatic or Independent ..... 203

Open 249

Removed From Pipe Bracket 246

Independent Brake Valve S-6 Complete . . . . 237

Removed from Pipe Bracket . . . . . -238

Reference Diagram . . . . . • . . . 241

Rotary Valve . . . . . . . . 240

Sectional View . . . . . . . 239

K-2 Passenger Locomotive ...... Frontispiece

Klinger Water Glass . . . . . . . . . 113

Large Duplex Air Gauge No. 1 . . . . . ■ . ■ . 192

Mallet Locomotive, Double Consolidated ..... 146

Boiler Extension and Feed Water Heater • . . . .148

McCord Force Feed Lubricator . . . . . . .102

How Oil is Applied to the Driving Boxes . . . .109

Lubricator Attachment . . . . . . .104

Section Through One Pump 105

Section Through Transformer . . . . . .107

Transformer Ratchet . . „ 108

Monitor Injector 87

Monitor Injector, Sectional View 88

Nathan Bull's Eye Lubricator 99

ILLUSTRATIONS 15

AGE

Nathan Sight Feed Glass and Fittings for Nathan Lubricator . ioo Non-Lifting Injector, Sectional View ...... 90

Piston Valve 59

Piston Valve and Arrangement of Ports in Steam Chest . . 60

Position of Brake Valve Handles 242

Quick Action Triple Valve, Release Position . . . . 252 Emergency Position . . . . . . . . 257

Service Application Position . . . . . .254

Reducing Valve C-6 . . . . . . . . 261

Safety Valve E-6 224

Sectional View of Steam Chest Slide Valve and Seat . . -55

Sellers' Injector . . . . 82

Sellers' Injector, Sectional View ....... 83

Simplex Injector, Sectional View . 86

Slide Valve Seat and Arrangement of Ports . . . 56

Slide Valve Showing Lead . . . . . . . 57

Small Duplex Air Gauge No. 2 ....... 192

Stay Bolts 38

Steam Gauge, Sectional View . • . • • • ■ .111

Stephenson Valve Gear . -67

Throttle Valve • ' . . 143

Throttle Valve Case .142

PRACTICAL INSTRUCTOR AND REFERENCE BOOK FOR

LOCOMOTIVE FIREMEN AND ENGINEERS

Part One THE FIREMAN'S DUTIES

i. To become a locomotive fireman the student will be required to make a sufficient number of trips under instruction of the engineer and fireman to learn his duties.

When the engineer is satisfied that the student can do the work of a fireman alone, the engineer will sign him up as being capable of performing the duties of a locomotive fireman.

2. The fireman must report for duty at the required time.

3. He must examine the bulletin board before starting on each trip.

4. He must assist (when conditions require it) in placing the required supplies on the engine, such as oil-cans, lanterns, torches, shovel, etc.

5. He will then see that all the necessary equipment which is supposed to remain permanently on the engine are in their proper places, such as coal pick, fire-hook and scraper, grate shaker, tank bucket, etc.

2 17

18 THE FIREMAN'S DUTIES

6. He will see that the signal equipment is in good condition and ready for use.

7. The signal equipment consists of one. red flag, two white flags, and four green flags; one red lantern, one white lantern, two classification lamps and two marker lamps. (Some roads require this equipment to include torpedoes and a fusee.)

8. The head-light, red and white lanterns and markers must be lighted at sundown and put out at sunrise, except when the view is obscured by fog or other causes, when lights may be used.

9. The classification lamps will be lighted and set to show green or white only by instruction of the engineer.

HOW TO FILL THE LUBRICATOR AND OTHER DUTIES

10. The first move to be made -in filling the lubricator is to see that all steam valves in connection with it are closed, by turning them to the right.

11. Now open the drain cock at the bottom of the lubricator and drain all of the water out of the bowl. It may be necessary to loose the filling plug at the top of bowl before all of the water will run out; then remove the filling plug and close the drain cock.

The lubricator is now ready for filling; fill the bowl with valve oil and replace the filling plug; now open the steam valve and the condensing valve wide open.

After the oil has become thoroughly heated in the lubricator the feed valves may be opened and adjusted to feed at the required rate.

THE FIREMAN'S DUTIES 19

12. After filling the lubricator the fireman will see that the cab is swept out, the boiler head wiped off, and the windows cleaned.

13. The fireman will now see that the fire is in proper condition for beginning the trip.

14. While on the road the fireman will endeavor to fire in such a manner as to maintain an average pressure of steam on the boiler.

The average pressure should be just a little less than the pressure at which the safety valves are set to open.

15. The fireman will take water and coal, and assist the engineer in making repairs when necessary. He will assist the engineer in keeping a look-out on the track for signals or obstructions, and call the indication of signals to the engineer. The fireman will take charge of the engine in the absence of the engineer.

16. He must not run the engine in the absence of the engineer, unless in some emergency he is directed to do so by the conductor or some one in authority.

17. The fireman must protect the front end of the train when necessary.

18. At the end of the trip he will assist in removing the supplies which are assigned to the engineer from the engine, when required.

19. The engineer turns in a time slip for the trip. The fireman's time is taken from this slip.

20. After the time slip has been turned in at the end of the trip the fireman is then relieved until called to go on another trip.

21. The fireman must be familiar with the rules that

20 COLOR SIGNALS

apply to the protection of trains, and the use of signals which he must be prepared to use promptly.

22. The fireman reports to and receives his instructions from the Road Foreman of Engines or Master Mechanic.

23. He must obey the orders of the Superintendent and Train Master.

24. When at the engine-house he is under the directions of the Engine-house Foreman.

25. When with the engine, the fireman must obey the orders of the Engineer respecting the proper use of fuel arid performance of his duties.

The fireman must be familiar with the following signals:

COLOR SIGNALS

26. Red — Means stop.

White — Proceed.

Green — Proceed with Caution (and for other uses prescribed by the rules).

Green and White— The Combined green and white is to be used to stop a train only at the flag station indicated on the schedule for that train.

Blue — Is a signal used by car repairers and air-brake inspectors to protect themselves while working about cars or engine.

While thus protected the cars or engine must not be moved until the signal has been removed by the same workmen who placed it there, and any obstruction must not be placed so as to obscure the view of such a signal.

27. A Fusee on or near the track, burning red, must

HAND, FLAG AND LAMP SIGNALS 21

not be passed until burned out. When burning green it is a caution signal.

HAND, FLAG AND LAMP SIGNALS

28. Swung across the track, Stop.

Raised and lowered vertically, Proceed.

Swung vertically in a circle at half arm's length across the track, when the train is standing, Back.

Swung vertically in a circle at arm's length across the track, when the train is running, Train has Parted.

Swung horizontally above the head when train is standing, Apply Air Brakes. Held at arm's length above the head when train is standing, Release Air Brakes.

Held horizontally at arm's length when train is moving, reduce speed.

Any Object Waved Violently on or near the track is a signal to stop.

ENGINE STEAM WHISTLE SIGNALS

29. One short blast of the whistle means Stop. Apply brakes.

Two long blasts — Release Brakes.

One long, three short— Flagman go back to protect the rear end of train.

Four long — Flagman return from the west or south on passenger track.*

Four long, one short — Flagman return from west or south on freight track.*

* Where three or more tracks are used as running tracks.

22 ENGINE STEAM WHISTLE SIGNALS

Five long — Flagman return from east or north on passenger track.*

Five long, one short — Flagman return from east or north on freight track.*

Three long when train is running — Train parted.

Three short when train is standing — Back the train.

Three short when train is running — Answer to conductor's signal to stop at next station.

Four short — Is a call for a signal.

Two short — Is an answer to any signal not otherwise provided for.

One long, two short — Used to call attention of other trains of the same or inferior class, that signals are being displayed for a following section.

Two long, two short — Used when approaching public road crossings at grade.

One long — Approaching stations, junctions, railroad crossings, etc.

A succession of short blasts of the whistle is a danger signal.

The explosion of two torpedoes, not more than two hundred feet apart, is a signal to reduce speed, and look out for a stop signal. One torpedo means the same as two, but the use of two is required.

AIR WHISTLE SIGNALS USED IN PASSENGER SERVICE

30. Two blasts when train is standing — Start. Two when train is running — Stop at once.

* Where three or more tracks are used as running tracks,

Three when train is standing — Back.

Three when train is running — Stop at Next Station. Four when train is standing — Apply or Release Air Brakes.

Four when train is running — Reduce Speed. Five when train is standing — Call Flag. Five when train is running — Increase Speed.

31. A chemical analysis of the elements entering into combustion together with their change in form and effect during the process of combustion proves that a careful study of the subject will be of great value to the locomotive fireman or engineer, not only in the economical use of fuel and abatement of smoke, but in general efficiency and the saving of labor as well.

32. The process or action of fire in consuming a body, as the burning of wood or coal, is generally known as combustion.

33. Combustion is accomplished by the union of an inflammable substance with oxygen.

In the burning of a substance heat is disengaged or thrown off and oxygen is absorbed.

Combustion therefore is the disengagement of heat, or heat and light, which accompanies certain forms of chemical combination.

34. Bituminous coal being the fuel most generally used by the different railroads, we will first consider its composition, and then the relation of other elements to its

24 THE ATMOSPHERE

composition, and the effect they have in obtaining the most effective combustion.

Bituminous coal is composed of from 50 to 80 parts fixed carbon.

Table showing the average analysis of Ohio coal.

Fixed carbon . 61 per cent.

Volatile matter -33 ■■" "

Ash 3 f " "

Sulphur i " "

Moisture ij " "

Total ........... . ioo per cent.

THE ATMOSPHERE

35. The atmosphere is a mechanical mixture and its two main constituents exist very nearly as follows in volume: Oxygen, 20.61 per cent; nitrogen, 77.95 per cent.

Table giving the average composition of air in detail.

Oxygen , 20 . 61 per cent.

Carbon dioxide o . 04 " "

Water vapor 1 . 40 " "

Nitric acid Trace.

Ammonia "

Total 100 per cent.

36. Table showing the composition of water.

Oxygen 88 . 8 parts by weight.

Hydrogen 1 1 . 1 " " " .

Carbon 1 " " Cl

Total 100 parts by weight.

DEFINITIONS 25

In order that the meaning of all the terms used in explaining the composition of the different elements necessary to combustion may be thoroughly understood, a list of definitions is given.

DEFINITIONS

37. Carbon — An elementary combustible substance, existing pure and crystallized in the diamond, and sometimes in graphite, and forming the basis of animal and vegetable charcoal and coke. It is the chief constituent in coal.

38. Carbon Dioxide — With water gas, is the product of complete combustion.

39. Carbon Monoxide — With water, vapor is the product of incomplete combustion.

40. Hydrogen — One of the elements of water, of which it contains one-ninth part. Hydrogen gas is the lightest body known; it is extremely inflammable.

41. Oxygen — Is the vital part of the atmosphere, and is the supporter of combustion.

42. Nitrogen is the principal ingredient of atmospheric air, and under ordinary conditions is non-combustible; its chief function is to dilute the oxygen.

THE PROCESS OF COMBUSTION IN DETAIL

43. The minimum quantity of air required for the combustion of one pound of bituminous coal is 143 cubic feet, but "under ordinary working conditions from 225 to 250 cubic feet is required.

26 PROCESS OF COMBUSTION

44. When carbon burns in a free current of air with ample oxygen present to complete the combustion, 12 parts by weight of carbon unite with 32 parts of oxygen to yield carbon dioxide.

45. Hydrogen is expelled from the coal at a fairly low temperature in combination with some of the carbon. This combination of gas is inflammable at a fairly low temperature, producing a flame which surrounds the fuel heating it and producing more gas. This leaves the remainder of the fuel in a porous condition and helps to make the combustion more complete.

46. The more pure carbon the coal contains the less flame will be produced by its combustion.

47. Soft coal consists to a large extent of volatile matter. All of the hydrogen or hydro-carbons of the volatile portions burn first; then if there is a sufficient amount of oxygen, the carbon combined with the hydro-carbons burns and finally the fixed carbon. This action does not take place separately but forms a combination.

48. The elements entering into combustion with oxygen are hydrogen and carbon, the hydrogen burning to water vapor, and the carbon producing either carbon monoxide or carbon dioxide, according to the volume of oxygen present.

49. Water vapor and carbon dioxide are the results of complete combustion.

50. Water vapor and carbon monoxide are the results of incomplete combustion, the carbon monoxide being capable of further combustion with a fresh supply of air.

51. Under ordinary conditions when building a fire in

PROCESS OF COMBUSTION 27

a furnace about one and one-half to two per cent of the carbons and hydro-carbons liberated escape from the stack unconsumed, but as the mass of fuel becomes thoroughly ignited and the furnace heated, the volume of smoke becomes much less. As the temperature of the furnace is now increased to a point where nearly all of the combustible gases are being consumed, the fire will burn clear and bright.

52. When a fresh supply of coal is fired, the temperature of the fuel and the quantity supplied will exert some influence on the temperature of the furnace.

53. In order to ignite the new fuel it must be heated to a temperature of a little over i,8oo° Fahrenheit.

54. If a large quantity of coal is fired at each firing, the temperature of the furnace will be reduced to such a degree that all of the combustible gases will not be consumed. The result will be a large volume of smoke, and a corresponding loss in the amount of effective heat generated per pound of coal consumed.

55. In order to secure the greatest per cent of efficiency per pound of coal, it should be fired often in a quantity that will just supply the rate of consumption.

56. The smoke which is expelled from the stack of a locomotive is composed of a very complex mixture and consists of unburnt carbon, tar vapor, and carbon monoxide gas, with small particles of ash and coked coal, which are drawn from the furnace by the force of the draft.

57. The density of the smoke depends particularly on the volume of unconsumed carbon which it contains.

28 PROCESS OF COMBUSTION

The gas arising from this volume of cooling carbon is monoxide gas and is very poisonous, and if breathed in large volumes, amounting to five per cent of the atmosphere, will cause death.

58. A British thermal unit is the amount of heat required to raise one pound of water i° Fahrenheit.

59. One pound of coal will produce from 11,500 to 14,000 British thermal units.

60. And evaporate from five to eight pounds of water.

61. The latter per cent of efficiency is seldom obtained because of the loss from several sources, such as improper firing, defective draft, faulty construction, and carelessness in the care of the boiler.

62. The rate of combustion varies according to the nature of the service, and will fluctuate between 20 and 140 pounds per square foot of grate surface per hour.

63. The average evaporation is about seven pounds of water per pound of coal.

64. A gallon of water weighs eight and one-third pounds, and if one gallon of water is evaporated per pound of coal, it is considered exceptionally good.

65. It has been shown that air is just as necessary as coal to produce combustion.

66. When no heat is lost and perfect combustion is obtained as in a testing plant, only 143 cubic feet of air is necessary to burn one pound of coal, but in actual practice with the locomotive about 19 pounds or 250 cubic feet of air per pound of coal is necessary to insure complete combustion.

PROCESS OF COMBUSTION 29

67. The supply of air to the furnace should be regulated in proportion to the amount of fuel to be consumed.

68. By admitting too much air to the furnace the excess draft will cool the gases below the igniting-point ; the excess air, becoming heated, passes out through the stack at a high degree of temperature, carrying a large quantity of unconsumed gases with it.

69. Air must be admitted to the furnace in such a way and in such volume that the temperature necessary to burn the coal and gases can be maintained.

70. Most of the air necessary to complete combustion can be admitted through the grates, passing up through the fire, burning the coked coal first, and forming carbon dioxide. As the air comes in contact with the fresh coal on the surface of the fire and joins with fresh carbon, carbon monoxide is produced.

71. If sufficient oxygen is not present at this time, a part of the gases will pass out through the stack unconsumed, but if a fresh supply of air is admitted to the surface of the fire, the carbon monoxide will combine with the oxygen in the air thus supplied and form carbon dioxide, completing combustion.

72. A small amount of air admitted to the fire-box above the surface of the fire, especially when the fire has become dirty, is very beneficial,, and for that reason the dampers in the fire door should be regulated accordingly.

73. The front dampers of the ash-pan should be kept closed as long as sufficient air can be supplied through the back ones.

74. The highest temperature that can be maintained in the fire -box under ordinary conditions by the combustion of bituminous coal is a little over 2,000° Fahrenheit, 2,200° Fahrenheit being the maximum heat obtainable under working conditions.

75. The greater part of the heat produced by the combustion* of coal in the fire-box is absorbed by the water in the boiler and it is due to this fact that the furnace is kept from attaining a higher temperature.