UC-NRLF 8 ^ ats LI BRARY OF THE UNIVERSITY OF CALIFORN: OF Received A ccessions No . // ^ /^//. Shelf No . UJTIVERSITT 2 w H H 3 8 H ft 03 W fc H 8 Si THE MODEEN PRACTICE OP BOILEE CONTAINING OBSERVATIONS ON THE CONSTRUCTION OF STEAM BOILERS; AND UPON FUENACES USED FOE SMOKE PREVENTION, WITH A CHAPTER ON EXPLOSIONS. BY ROBERT ARMSTRONG, C. E., CONSULTING ENGINEER. REVISE D, WITH THE ADDITION OF NOTES, AND AN INTRODUCTION BY JOHN BOURNE, ESQ. llonfcon : E. AND F. N. SPON, 16, BUCKLERSBURY. 1856. [Sight o/ Translation reserved."] CONTENTS. PAGE DEDICATION to Robert Stephenson, Esq., M.P.,F.R.S.,&c. vii PKEFACE ix INTRODUCTION BY JOHN BOURNE, ESQ., C.E 1 High. Pressure Steam 2 Smoke-burning 7 Explosions 8 D. K. Clark's table from Regnault's experiments 12 CHAP. I. ON BOILERS GENERALLY, and a radical reform in those for marine purposes suggested 17 Hay-stack boiler 18 Waggon Boiler 19 Boulton and Watt boiler 21 Marine boilers 27 The Galloway conical tube boiler 33 Kennedy's water meter 38 Exhibition boiler of 1851 53 Elephant boiler 69 Dunn's patent retort boiler (Fig. 1) 77 Galloway's patent marine boiler (Fig. 2) 80 CHAP. II. SMOKE PREVENTION and its fallacies 81 'Losh's double furnace system 87 Ditto as applied by R. Armstrong 87 Ditto by J. Bourne 90 Smoke-burning by John Wakefield 93 Ditto by J. Parkes 95 Universal Argand fire-grate 96 Copy of report on Williams's patent furnace 10*2 VI CONTENTS. PAGE ACCOUNT OP EXPERIMENTS at Houldsworth's FACTORY IN MANCHESTER, on the economy of smoke preven- tion Ill SUMMARY OP RESULTS of experimental trial of the com- parative economy of Mr. C. W. Williams' s patent system of smoke prevention, and the ordinary plan 1 14 A theory of the BEST POSSIBLE COMBUSTION 116 CHAP. III. EXPLOSIONS : an investigation into some of the causes producing them, and the deterioration of boilers generally 121 Experimental explosion (Fig. 3, p. 124) 123 The Cross Lane, Manchester, explosion 126 The Jersey Street ditto ditto 127 Sticking of safety valves 128 Deficiency of water 131 Loss of water by blowing off and leakage (fig. 4, p. 134) 133 Contrary conclusions drawn 138 Practical application of preceding principles 143 Defects of riveted plates 146 Fig. 5, p. 149, Fig. 6, p. 150. How change of form by expansion produces fracture . . 156 Fig. 7, p. 156, Fig. 8, p. 158. NOTES to Chap. III. A. Explosion at Brookes's Flax mill, Bolton 162 B. Spheroidal condition of water 168 APPENDIX : No. 1. Review of C. W. Williams's book, by J. Bourne, Esq 175 No. 2. American experiments on explosions 187 TO EOBEET STEPHENSON, ESQ., C.E., PRESIDENT OF THE INSTITUTION OF CIVIL ENGINEERS, H.P., F.R.S., &C. &C. EESPECTED SIR, I venture to dedicate these pages to you, both as a manifestation of my reverence for the memory of your late Father, of whose genius and persistency I was for many years an admiring spectator ; and as a slender token of my sense of your own eminent talents as an engineer, and of your estimable personal character. While some engineering reputations are known to rest on diplomatic adroitness, and others are alto- gether hollow and conventional, it is known to be your great distinction that the fabric of your fame is as solid as it is imposing, and is held in most esteem by those whose pursuits best enable them to judge of its quality. I am, dear Sir, faithfully yours, E. AEMSTEONG. PREFACE. THE design of the present work is to place the reader in possession of sound information re- specting some of the best kind of boilers at pre- sent in use, and also to indicate the course which future improvements to be efficient and of material benefit must necessarily pursue. The subject of smoke-burning which is reckoned one of the important topics of the present day I have endeavoured to illus- trate in such a manner as both to correct the erroneous and exaggerated statements made by interested patentees, and to convey just and moderate ideas upon that subject. The explosions of boilers is a question still involved in much obscurity, some of which X PREFACE. will I hope be dissipated by the remarks I have offered, and as the general introduction of steam of a higher pressure seems to be ine- vitable, this is a subject which more than heretofore stands in need of elucidation. I have much gratification in being able to present the present work enriched by the additions and corrections of MR. BOURNE, which he has kindly furnished in conformity with the friendly feeling which he has con- stantly manifested towards me for many years. R. AEMSTEONG. 65, Fenckurch Street, London, 1856. 0* INTRODUCTION. BY JOHN BOURNE, ESQ. 9. BILLITER STREET, FENCHURCH STREET, LONDON. MR. ARMSTRONG lias requested me to revise and add some notes to his present work on steam boilers ; a task which my esteem for him has induced me wil- lingly to undertake, though I do not know that any remarks of mine upon this subject can add weight to the doctrines of so established an authority. It is well known to engineers that Mr. Armstrong has had a more extended experience, and possesses probably a more accurate practical acquaintance with boilers and furnaces than any other person now living, and the public has reason to feel grateful that an engineer of such eminent capacity upon these subjects vouchsafes to offer them the fruits of his long and extensive practice. Of all kinds of books there are none so exhausting as books upon practical engineering. Truths of the most eminent value, and results which it may have B 2 CONVERTIBILITY OF HEAT AND POWER. required painful labour to collect are despatched in the compass of a few brief sentences, without any manifestation, at least to the cursory reader, of the toil and reflection involved in the brief exposition. Such works are in fact the essence of thought. There are consequently few of them written, and it ought to be appreciated as a service to humanity when such men as Mr. Armstrong come forward to lay before the public results which it has taken a life of labour to attain. The three topics of which Mr. Armstrong has mainly treated in the present work are, first, The Ne- cessity of Strong Boilers; second, Smoke-Burning; and third, Explosions. Upon each of these topics I propose to offer a few remarks, partly in recapitulation of what Mr. Armstrong has said, and partly as exhibit- ing the results of my own experience, or the nature of my own opinions on those subjects. HIGH PRESSURE STEAM. Eecent investigations have led to the discovery that heat and power are mutually convertible, and we are able to tell what rise of temperature the expenditure of a given amount of mechanical power would impart to water, and reciprocally what quantity of power a NECESSITY OF STRONGER BOILERS. 3 given quantity of heat if used in a perfect engine would produce. One result of this discovery is the manifestation of the great loss of power in the best existing steam engines. The best class of Cornish engines do not utilize above one tenth part of the heat expended in working them, so that in the best engines about nine tenths of the power is lost. The theoretical condition under which we would obtain the full effect of the heat in a steam engine consists in heating the water to the temperature of the fur- nace, and in suffering this superheated water to ex- pand under such circumstances, that during its expansion it would produce power. In ordinary engines, however, tins condition cannot be observed, but it will be approached by using steam of a high pressure and of an elevated temperature. The eco- nomy of fuel has now become an object of paramount importance in engines of every class, but more espe- cially so in the case of steam navigation ; as there, not merely the expense of the fuel but the expense of carrying it must be incurred. To attain even a mo- derate measure of economy, steam of a high pressure and elevated temperature is indispensable, and if we have steam of a high pressure we must have a class of boilers introduced into steam vessels which will be 4 NECESSITY OF STRONGER BOILERS. able to bear it. Mr. Armstrong lias addressed some of his remarks to this important question, and his opinion seems to be that a modification of that species of boiler termed sometimes the French boiler, and sometimes the Elephant boiler is the most suitable for the altered circumstances of steam navigation. It is clear that a boiler, to be able to bear a high pressure with safety, and without being encumbered with need- less stays, should be a boiler with a cylindrical shell, not too large in diameter. The furnace of such a boiler may either be within it or beneath it. I cannot say that I think internal furnaces very safe with high pressures. If they get even slightly out of shape they are liable to collapse ; and whereas, in the case of a cylindrical shell, the tendency of the internal pressure is to restore the cylindrical form should it nave been accidentally disturbed, in the case of a cylindrical flue or furnace-tube where the pressure is external, the tendency of the pressure is to destroy the cylindrical form, should it have been disturbed accidentally, by overheating or otherwise. My opi- nion, therefore, is, that a fire beneath the boiler is, so far as regards safety, better than a fire within it, sup- posing that the water is clean and that there is no deposit. In marine boilers, however, there is a sedi- ECONOMY OF HIGH TEMPERATURE IN CYLINDER. 5 ment lite mortar, which, if allowed to subside to the bottom of the boiler, and a fire be, at the same time, applied to the bottom, will cause the iron to be burned. But by providing collecting vessels within the boiler the deposit will take place within them, and may be from thence blown out into the sea ; and if the operation of blowing off the boilers be suffi- ciently practised, there will, in point of fact, be no sediment at all. By the application, therefore, of such simple expedients as a collecting vessel and a continuous blow-off, boilers may be employed for marine purposes which will not accumulate scale; and, if the formation of scale be prevented, a species of boiler may be used which will enable high pressure steam to be employed with safety. Steam of this kind, used expansively in the engine, will maintain any required speed of the vessel with a much smaller consumption of coal than would otherwise be required. In all engines working expansively it is important to maintain the temperature of the cylinder as high as possible, since the temperature of the steam is diminished, and a portion of it is even condensed within the cylinder in consequence of the communi- cation of mechanical power to the piston. For, as a 6 CAUSES OF CONDENSATION IN CYLINDER. certain weight of steam has a certain mechanical equi- valent which would be realized if the steam could be used in an engine without waste, it follows that the steam, in so far as it exerts power, must lose heat, else it would have both the power and the heat, which is impossible. Accordingly, it is found that there is a larger condensation in the cylinder of an engine which is at work than would lake place if the engine were not at work, although the steam is admitted to the cylinder freely in both cases. When the engine is stationary the whole condensation is that caused by the radiation of heat : when the engine is at work we have, besides this cause, the communication of mechanical power to the piston, which can only be effected at the expense of some of the heat, and therefore, with a certain condensation of the steam within the cylinder. In a perfect engine there would be no heat discoverable in the condenser, as the whole would have been changed into mechani- cal power ; and, in all engines, there will be an infe- rior quantity of heat in the condenser to that which leaves the boiler, by the equivalent in heat of the mechanical power generated in the engine. Steam- jackets act in counteracting the condensation caused bj the communication of power. NEW " SMOKE-BURNING FURNACE. 7 SMOKE-BURNING. With respect to smoke-burning, the best species of furnace for the accomplishment of this object, with- out the introduction of countervailing evils, is one which Mr. Armstrong has designed for Woolwich Dock Yard, on a nearly similar plan to several erected by him in the Arsenal. In this furnace the foremost length of bars slopes somewhat towards the mouth ; whereas, the after lengths of bars slope in the contrary direction, or towards the bridge. At the ridge where the opposite slopes meet, there is a doable bearing bar which permits some air to enter the furnace in that situation. The coal in the foremost length of bars is maintained in rapid combustion, whereas the coal upon the after tier of bars is undergoing a slow distillation. In charging the furnace, the coal is thrown chiefly to the back end, so that the surface of the fuel slopes forward from the bridge towards the furnace mouth. This coal,, being lighted on the top, becomes a kind of coal torch. The gas generated by the heat, in passing through the ignited stratum on the surface, is consumed ; and, from time to time, the ignited embers, from which the gas has been expelled, are raked forward, and fresh coal is thrown in to maintain the combustion. Yery little smoke is 8 ADVANTAGES OF FIRE-FEEDING MECHANISM. evolved from this species of furnace; and it differs little from a common furnace, either in construction or efficiency."* The best species of furnace, however, for marine purposes, is one which, while fulfilling all other indi- cations, will feed the fire by self-acting mechanism. The firing may be accomplished by some of these expedients, not merely in a more efficient manner, but at a materially diminished expense. In the case of a boiler on land, in which a man to look after the engine and boiler is required in any case, the intro- duction of a firing machine to do a portion of his work is not an object of much importance. But in the case of the furnaces of a steam vessel, which require a number of men to attend upon them every watch, an important economy would be accomplished by the substitution of mechanism of an efficient character. | EXPLOSIONS. The subject of boiler explosions is still involved * A representation of this newly designed furnace, as applicable to an " Elephant" Boiler, suitable for dockyards, saw mills, &c., where waste timber and other varieties of mixed fuel are used, is given in the frontispiece. CAUSES OF EXPLOSIONS. 9 in a good deal of obscurity. No doubt, a frequent, and, probably, the most frequent, cause of explosion, is the sudden generation of steam produced when the water-level has been allowed to fall so low that the flues get very hot ; and then is suddenly raised, so that the water comes into sudden contact with the heated metal. But there are other cases, in which the water is repelled from the iron by a strong heat, though no undue subsidence of the water-level has been suffered to take place. There are boilers in which the natural order of things is reversed Avhen heat is applied, the water being mostly in the top part of the boiler, and the steam in the bottom. Such boilers necessarily prime very much; or, in other words, much water passes into the steam-pipe, and, at the same time, the part of the boiler on which the flame acts is liable to become overheated from the absence of water in contact with the metal to conduct away the heat. There are boilers in which a lead rivet in the flues may, at any time, be melted out by firing very strongly; the water being so far repelled by the heat as to enable the tempera- ture of the metal to rise to the melting point of lead. In all boilers in which there is ebullition going on, the apparent level of the water will be greater 10 DANGEROUS AMATEUR SMOKE PROJECTS. than tlie true level, as the admixture of steam swells the water, producing what is called " false water/' by the drivers of locomotives. One effect of this ficti- tious augmentation of bulk is, that when additional feed water is turned on, from the water level becom- ing too low, the first effect is still further to lower the water level. This anomaly is caused by the conden- sation of the steam mixed with the water of the boiler, when an additional quantity of cold or cool water is introduced; but the water level may, at such times, be again raised by easing the safety-valve, which will enable the steam mixed with the water to swell to larger dimensions when the pressure is reduced, and thus compensate for the partial conden- sation which the introduction of additional feed water has caused. One cause of boiler explosions Mr. Armstrong considers to be the unskilful application of smoke- burning projects, which, by producing violent alter- nations of temperature in the boiler bottom, loosen the riveted joints, and, finally, cause them to give way. The occurrence of an accident of this kind in a boiler fitted with the smoke-burning furnace of Mr. Charles Wye Williams has led to a wordy war, which has been waged by that lively gentleman MR. CLARK'S RESULTS WITH LOCOMOTIVE BOILERS. 11 for many years. Mr. "Williams is a species of ama- teur engineer ; who, on the strength of an acquaint- ance with the atomic theory, and other elementary chemical truths, acquired, apparently, late in life, has set up as the engineering reformer of the age, in the department of smoke-burning; and he has obtained the approbation of the " Mechanic's Magazine" and other oracles of corresponding authority. A man's ambition need not be very exalted, which is satisfied with such successes; but if there be gratification sufficient to compensate the ridicule arising from harping eternally upon a single trumpery topic, there is no reason, that I know of, why it should not be possessed. The subject of locomotive boilers has been treated more fully by Mr. D. K. Clark, in his excellent work on ' ' Eailway machinery/' than by any other author, and he has shown that it is inadvisable to make the area of fire-grate or the area of the chimney very large, that the smoke box should not be of greater capacity than is absolutely necessary to collect the hot air from the tubes, and that the blast-pipe should stop short, by a few inches, of the foot of the chimney, instead of penetrating into it. The follow- ing table is taken from Mr. Clark's work : TABLE OF THE PROPERTIES OF SATURATED STEAM ; FROM REGNAULT'S EXPERIMENTS. Total pressure per Relative volume. Temper- ature. Total Heat. Weight of one inch. cubic foot. Ihs. Fahr. Fahr. Ibs. 15 1669 213 1 1178-9 0373 16 1572 216-3 11799 0397 17 1487 219-5 11809 0419 18 1410 222-5 1181 8 0442 19 1342 225-4 11827 0465 20 1280 228-0 1183-5 0487 21 1224 2306 11843 0510 22 1172 233-1 1185-0 0532 23 1125 235-5 1185-7 0554 24 1082 237-9 11865 0576 25 1042 2402 1187-2 0598 26 1005 242 3 1187-9 0620 27 971 244-4 1188-5 0642 28 939 246-4 1189-1 0664 29 909 248-4 1189-7 0686 30 881 250-4 1190-3 0707 31 855 252-2 1190-8 0729 32 830 254-1 1191-4 0751 33 807 255-9 1192-0 0772 34 785 257-6 1192-5 0794 35 765 259-3 1193-0 0815 36 745 260-9 1193-5 0837 37 727 262-6 1194-0 0858 38 709 264-2 1194-5 0879 39 693 265-8 U95-0 0900 40 677 267-3 1195-4 0921 41 661 268-7 11959 0942 42 647 270-2 1196-3 0963 43 634 271-6 1196-8 0983 44 621 273-0 1197-2 1004 45 608 274-4 1197-6 1025 EEGNAULT^S TABLE OF PROPERTIES OF STEAM. 13 (Continued.) Total pressure per square inch Relative volume. Temper- ature. Total Heat. Weight of one cubic foot. Ibs. Fahr. Fahr. Ibs 46 595 2758 1198-0 1046 47 584 277-1 1198-4 1067 48 573 278-4 1198-8 1087 49 562 2797 1199-2 1108 50 552 281-0 1199-6 1129 51 542 2823 1200-0 1150 52 532 283-5 1200-4 1171 53 523 284-7 1200-8 1192 54 514 2859 1201-1 1212 55 506 287-1 1201-5 1232 56 498 288-2 1201-8 1252 57 490 2893 1202-2 1272 58 482 290-4 1202-5 1292 59 474 291-6 1202-9 1314 60 467 292-7 1203-2 1335 61 460 293-8 1203-6 1356 62 453 294-8 1203-9 1376 63 447 295-9 1204-2 1396 64 440 296-9 1204-5 1416 65 434 298-0 1204-8 1436 66 428 2990 1205-1 1456 67 422 300-0 1205-4 1477 68 417 300-9 1205-7 1497 69 411 301-9 1206-0 1516 70 406 302-9 1206-3 1535 71 401 303-9 1206-6 1555 72 396 304 8 12069 1574 73 391 305-7 1207-2 1695 74 386 3066 1207-5 1616 75 381 307-5 1207-8 1636 76 377 308-4 1208-0 1656 77 372 309-3 1208-3 1675 78 368 310-2 1208-6 1696 79 364 311-1 1208-9 1716 80 359 312-0 1209-1 1736 TABLE OF THE PROPERTIES OF SATURATED STEAM j FROM REGNAULT'S EXPERIMENTS. (Continued.) Total pressure per square Relative volume, Temper- ature. Total Heat. Weight of one cubic foot. inch. Ibs. Fahr. Fahr. Ita. 81 355 312-8 1209-4 1756 82 351 313-6 1209-7 1776 83 348 314-5 1209-9 1795 84 344 315-3 1210-1 1814 85 340 316-1 1210-4 1833 86 337 316-9 1210-7 1852 87 333 317-8 1210-9 1871 88 330 318-6 1211-1 1891 89 326 319-4 1211-4 1910 90 323 320-2 1211-6 1929 91 320 321-0 1211-8 1950 92 317 321-7 12120 1970 93 313 322-5 12123 1990 94 310 323-3 12125 2010 95 307 324-1 1212-8 2030 96 305 324-8 1213-0 2050 97 302 325-6 1213 3 2070 98 299 326-3 1213-5 2089 99 296 327-1 1213-7 2108 100 293 327-8 12139 2127 101 290 328-5 1214-2 2149 102 288 329-1 1214-4 2167 103 285 3299 1214-6 2184 104 283 3306 1214-8 2201 105 281 331-3 1215-0 2218 106 278 331-9 1215-2 2230 107 276 332-6 1215-4 2258 108 273 333-3 1215-6 2278 109 271 334-0 1215-8 2298 110 269 334-6 1216-0 2317 HI 267 335-3 1216-2 2334 REGNAULT'S TABLE OF PROPERTIES OF STEAM. 15 (Continued.) Total pressure per square inch. Relative volume. Temper- ature. Total Heat. Weight of one cubic foot. Ibs. Fahr. Fahr. Ibs. 112 265 336-0 1216-4 2351 113 263 3367 1216-6 2370 114 261 337-4 1216-8 2388 115 259 338-0 12170 2406 116 257 338-6 1217-2 2426 117 255 339-3 1217-4 2446 118 253 339-9 12176 2465 119 251 340-5 1217-8 2484 120 249 341-1 1218-0 2503 121 247 341-8 1218-2 2524 122 245 342-4 1218-4 2545 123 243 343-0 12186 2566 124 241 343-6 1218-7 2587 125 239 344-2 12189 i -2608 126 233 344-8 1219-1 2626 127 236 345-4 1219-3 2644 128 234 346-0 1219-4 2662 129 232 346-6 1219-6 2680 130 231 347-2 1219-8 2698 132 228 348-3 1220-2 2735 134 225 349-5 1220-6 2771 136 222 350-6 1220-9 -2807 138 219 351-8 12212 -2846 140 216 352-9 1221-5 2885 142 213 354-0 1221-9 2922 144 210 355-0 1222-2 2959 146 208 356-1 1222-5 2996 148 205 357-2 1222-9 3033 150 203 358-3 12232 3070 160 191 363-4 1224-8 3263 170 181 368-2 1225-1 3443 180 172 372-9 12277 3623 190 164 377-5 1229-1 3800 200 157 381-7 1230-3 3970 16 CONCLUSION. With these cursory remarks I dismiss Mr. Arm- strong's present work. Its main suggestions, namely, the necessity of the adoption of cylindrical boilers in all cases in which economy of fuel is important, the practicability of burning smoke by simple arrange- ments without, however, the accomplishment of much, if any direct saving of fuel, the advantage of fire feeding mechanisms in steam vessels, and the doctrine of the accidental deficiency of water in boilers being the main cause of explosions, are all, in my judgment, sound doctrines, and, if so, public benefit cannot fail to arise from their wide acceptation. J.B. KOTE TO REG:N T A TILT'S TABLE, PREVIOUS PAGE. The above table of corresponding pressures, temperatures, and volumes of saturated steam is by the kind permission of Mr. Clark copied from his valuable work. The pressures and temperatures are the direct results of M. Regnault's experiments. The relative volumes are obtained by means of the formula P The fourth column is the result of direct experiment by llegnault. And the fifth column is calculated by dividing 62-321 lb., the weight of a cubic foot of water at 62 by the relative volume. 17 CHAPTER I. ON BOILERS GENERALLY, AND A RADICAL REFORM IN THOSE FOR MARINE PURPOSES SUGGESTED. THE main design of this short essay is to impart in few words, that information respecting boilers and furnaces, which persons employing steam-engines, desire to possess, but which they have not much time to acquire. While yielding our approbation to all investigations touching the science of steam, which seem likely to illustrate its nature, we are at the same time conscious that the bulk of mankind immersed in active business, have but little time for such speculations; and it is our design rather to state results, and enunciate general laws, such as are found to govern successful practice, than to embark upon the wide sea of theoretical disquisition, or to announce any mere theoretical conclusions. Still less is it our intention to parade the elementary truths of che- mistry as baits for the admiration of the ignorant expanded into all the forms proper to laborious dul- c 18 THE HAY-STACK BOILER. ness and varied in every phrase of emphatic iteration. That task has already been performed by Mr. Charles "Wye Williams in his work on the " Combustion of Coal and the Prevention of Smoke/' and the merits in which that work is deficient have been compen- sated by its artificial notoriety. We should be sorry to deprive Mr. Williams of any portion of the repu- tation which has cost him so much and the quality of which seems to satisfy his ambition, and there is cer- tainly no danger that in the present work we shall run into any similar extravagance, having so painful an example before us of this species of folly. To theory we take no exception, theory being indeed only the connection of individual facts into such a chain as to constitute a natural law. HAY-STACK BOILER. This boiler is termed the hay-stack boiler from its shape. In some districts it is called the balloon boiler, and the kettle boiler. It is a good kind of boiler up to 10 or 12-horse power, and 10 or 12 Ibs. pressure, where boilers are required to stand singly. It is strong enough within those limits, and has the greatest capacity for the least quantity of material THE WAGGON BOILER. 19 employed. Independent of its economy, which, with inferior fuel, need not be less than that of any other kind, it has, perhaps, the greatest evaporating power for its dimensions, and if set up, as it usually is, with a single wheel draft, it requires only a small chimney. The shape of the bottom of this boiler is generally not so well adapted as some other kinds of boilers for applying the usual arrangements for consuming smoke, but if made of copper, as such boilers are in some of the London breweries, they admit of coke being used to very great advantage. In Staffordshire, and some other mining districts, the hay-stack boiler has been frequently made much too large ; and where this defect has been sought to be corrected, by carrying the flue spirally twice round the boiler, the result has usually been unsuccessful, if not dangerous. THE WAGGON BOILEK. This boiler is, in principle, the hay-stack boiler just described, only put into an oblong instead of a circular form on the ground plan. It therefore per- mits of facilities in arranging a number of boilers side by side without wasting space. It is distin- PROPERTIES OP THE WAGGON BOILER. guished in mining districts as the oblong boiler. In other places it is sometimes called the caravan boiler, and by Mr. Wicksteed, the waggon-head boiler. It possesses some advantage over the hay-stack boiler in its being better adapted for the use of rich bituminous or flaming fuel, and Newcastle coal generally. It admits of being made of such a length, that the flame from a well-managed fire will be generally expended before reaching the end; and it can be easily varied in its proportions to suit the many varieties of flaming fuel wood as well as coal. As flaming coal is also smoky coal, the waggon boiler from its rectangular plan, is suitable for the application of such coal, because it admits of the ordinary rectangular fire- grate, with convenient space beyond for any ar- rangement of the furnace chamber and bridges, so as to meet almost any requirement for smoke-consuming purposes. The waggon boiler is, except in the direction of its length, nearly as strong as the hay-stack boiler, up to 5 feet diameter, and if provided with one, two, or three longitudinal stays, and 4 such stays of \\ inch square from end to end if above that diameter, together with cross stays at every two feet in the length, it may be safely worked up to 10 Ib. on the WAGGON BOILERS WITH INTERNAL FLUES. 21 square inch. For this pressure it is usually made of plates to average inch thick all round, the top being never less than , and the ends ought to be seven- sixteenths of an inch. Up to 20 or 25 horse-power, boilers which are as many feet in length by 5 to 5 \ feet wide, or equivalent proportions, made in this way, will weigh 17 or 18 Ib. per square foot of total surface, inclusive of nvets, overlap of plates, stays, &c. 17 or 18 square feet of such surface, may be reckoned as equivalent to a horse-power; from these data, the weight and cost (at present 25 to 30 shil- lings per cwt.) is soon obtained. Within the above limits, no boiler ever made can exceed this one in efficiency, economy, and durability, if well-proportioned to the engine it works, and to the fuel supplied to it. If required of greater power than 20 or 25 horse, boilers of this kind are made deeper in proportion to their length, and an internal flue tube is introduced, and such boilers are then called the BOULTON AND WATT BOILER. This boiler, when of 30 or 40 horse-power, is more economical in fuel than the plain waggon form ; but is weaker for the same thickness of iron, and ought 22 RULES FOR PROPORTIONING BOILERS. not to be worked at more than 8 Ib. per square inch. Its power is calculated in the same way as that of the waggon boiler, excepting only that the breadth or diameter of the internal tube is to be considered as so much added to the width of the boiler itself. Thus, if a waggon boiler of 20 feet long, by 5 feet wide, be equal to 20-horse power, being at the usual rate of 5 square feet of water surface, or horizontal ground plan per horse power, then a Boulton and "Watt Boiler of the same horizontal dimensions exter- nally, but having its inside flue tube of 2 feet dia- meter, will be two-fifths more powerful, or 28 instead of 20-horse power, it must be supplied, of course, with a proportionate increase of fire-grate, and is thus computed : Length 20 ft. x (5 + 2 =) 7 ft. wide = 140 = g Divided by 5 feet per H.P. 5 horse power. With these dimensions, however, it would have to be of very considerable depth, in order to have the required capacity for holding a sufficient quantity of water and steam for that power. It is therefore found preferable to make such boilers from 6 to 8 feet wide, by 8 or 9 feet deep, and they should never be more than 28 or 30 feet long. If a boiler of this RULES FOR PROPORTIONING BOILERS. 23 kind is not required to be above 40 horse power, there is no necessity, unless very bituminous coal is used, for its being much more than 20 feet in length. With that length it may be made 6 ft. 6" wide, by 8 ft. or 8 ft. 6" deep, and contain a circular flue-tube of 3 J ft. diameter. The computation in the same manner as above, will then stand as follows: 20ft.x(6ft. V + 3ft.6" =) 10ft. 200 = = - = ^U J.r. 5 5 As in my former works upon steam boilers, I gave some examples of the arithmetical calculations con- nected with this subject, at full length, for the spe- cial benefit of engine-men and stokers ; and having since ascertained the utility of such numerical exam- ples for the purpose intended, I shall give a similar example here : Width or diam. of boiler 6*5 feet. Ditto of inside flue-tube 3*5 10-0 Multiply by the length 20 Divide by 200 40-horse power. 24 ETJLES FOE PEOPOETIONING BOILEES. The slide rule formula for all such cases is, A | Gauge point 5 | or 5*7 | diam. of boiler and flue 10 <5 I Horse power 40 | 35 ["Length of ditto 20 If the second divisor or gauge point 5*7 be used, which gives about a square yard, or 9 square feet of effective heating surface per H. P v the result is seen to be only 35 H. P. But, by placing 40, the power required, opposite to 5-7 in the place of 35, we shall find, opposite to 10, the proper length to make the boiler 40-horse power at that rate, namely 22*8 feet as below, A [ 5-7 | diameter 10 | or 11 j. | 40 | length 22-8 | 20~ or, retaining the same length 20 feet as before, oppo- site to it is seen 11 as above, for the diameters of boiler and flue together, which may be conveniently made 8 feet, and 3 feet 6 inches respectively. A Boulton and Watt Boiler, thus proportioned, is much more economical of fuel than a waggon boiler of the same size or power ; but it requires more total surface of iron plate, although it is measured pre- cisely in the same way, that is, the lower half of all the flues is left out in the measurement, as non-effective in generating steam, and one half only of the vertical MODES OF STAYING BOILERS. 25 heating surface is considered as effective heating sur- face. In respect to strength, this boiler is weaker than the unflued waggon form, in proportion as its depth exceeds its diameter; notwithstanding it may be made of thicker plates in proportion to its increased size*. This defect is partially remedied by having two tiers of cross stays 1" square, placed one above, and the other below the inside flue. Besides these cross stays, it is usual to support the bottom of the boiler by oblique stays, commonly called "upright" stays, attached to the arch of the boiler bottom, and the other end secured by cotters upon, and near the ends of the upper cross stays. All these stays of which there are 4 for each plate in the length of the boiler, are attached by broad wrought iron straps and cotters, which last should not be made too taper, for when so, they are liable to wriggle loose by the working of the boiler. Besides the usual number of longitudinal stays from end to end, as in the plain waggon boiler, some per- sons put in " angle stays," extending from near the centre of each end, to the second or third plate on each side. Again, we occasionally find a stay carried obliquely downwards from the flat end of the boiler to the top of the flue tube, which we consider injudicious, 26 STAYING OF BOILERS. and rather tending to do harm than good. For the tube itself generally is, or should act as a stay from end to end ; and on that account should not be drawn out of its direct tensile action by any side attachment, liable to create lateral strain. The probable reason why stays were originally placed in this part by Boulton, Watt and Co., is that they did not latterly carry the flue-tube right through from end to end, but terminated it in a flat topped "take up" inside the boiler, to support the top plate of which this oblique stay assisted. With respect to similar oblique or angular stays carried from the ends to the arched top of the boiler, we cannot say much in their favour, although some of them have become popular under the name of "gusset" stays, from their being made of triangular plates instead of square bars, which would, we think, be more suitable, if needed at all. How- ever appropriate these gusset stays, or stay plates, instead of stay bars, may be in plate iron bridges and structures of that kind, where stiffness from external pressure and from twisting is the main object in view, any peculiar value they can have in resisting the internal strains to which steam boilers are subject, is not very apparent, especially when we consider that every unnecessary rivet, not to say seam of rivets, in a boiler is a source of weakness, not strength. WELDING OF BOILER PLATES. 27 If larger boiler plates could be manufactured, or could large plates be as easily ascertained to be sound as small ones, then the less rivetting the better. Since the new system of welding, instead of rivetting the edges of boiler plates together has been so far perfected by the patent process of Mr. Bertram, late of Woolwich Dockyard, as to prove its superior strength to even double rivetting, it is not now too much to look forward to the time when not only a boiler, but the iron hull of "the noblest machine that ever was invented " a SHIP, instead of being, as it may now be termed, "stitched" together in patches by " seams " and " gussets," will be forged in one entire piece ; at all events, Mr. Bertram has demon- strated the practicability of welding together iron plates in a cheap, rapid, and efficient manner, and there can be no doubt that his discovery must in time find many valuable applications. MARINE BOILERS. In this country marine boilers are almost all low pressure boilers, but the pressure has been gradually creeping up for several years, and pressures of from 20 to 301bs. on the square inch, are now by no means unusual. At the same time no corresponding 28 DEFECTS IN THE PRESENT improvements have been made in the structure of the boilers to ensure an equal measure of safety to that which previously existed. No doubt modern marine boilers are made of good iron, are well rivetted and are very much stayed. But the stays, especially in the region of the steam chest, are speedily corroded by the action of the steam ; the plates of the boiler also get thin, so that unless the engineer reduces the weights on the safety valve as the boiler gets worn, explosion will be apt to occur from mere weakness of the boiler. For tug boats and other commercial purposes, for war, and for sea-going vessels generally, we do not see how very high pressure, whether with condensing or non-condensing engines, and for war ships, extreme high pressure is to be avoided. The economy of the combined high and low pressure engine, and the ad- vantages of working very expansively, in various ways are so great, and so much more important afloat where the fuel has to be carried, than ashore, that it has long been a problem, whether it would not eventually be true economy to adopt the very strongest boilers which can possibly be made at once. Say to be able to work at not less than 100, and up to 200 Ib. on the square inch ; and we really see no very great CONSTRUCTION OF MARINE BOILERS. 29 difficulty in making boilers quite as safe from explo- sion at 200 Ib. as the ordinary marine boilers as now made, are at 20 Ib. pressure. It is merely a question of investment of capital, not in large ships, but in strong ships, so that we are inclined to side with those who would adopt such a system as good commercial policy. Because if the boilers are capable of working safely at 200 Ibs. there is no reason why, with proper arrangements, such boilers with suitable engines, should be less economical than ordinary boilers if worked at ordinary pressures. The greater cost of the boiler in the first instance will not only confer greater strength but greater durability. The present construction of the multitubular boiler, as it is called, may be truly stated as a disgrace to the science of this age of progress. The marine boiler yet remains, in fact, no more than a locomotive boiler, with the most important part of that boiler, the fire-box left out. It is not that we would put a fire-box, or anything like it, aboard a steam ship, though well adapted to the rail ; that is only suited for burning coke which is too bulky a fuel for marine purposes. Besides a blast or strong draft by some means seems a necessity for burning coke with ad- vantage. 30 SUGGESTIONS OF IMPROVEMENT Very much more, however, is either the blast or jet required, by reason of the multitude of small tubes through which the products of the combustion must be drawn. This creates an additional difficulty with the present marine boiler, and it is not likely that from 20 or 30 per cent, of its power can be afforded for blowing the fire, as is the case with some locomotives. What then, it may be asked, is the first step to improve the present practice? And my answer is ready, If a moderate improvement only is permitted, without greatly disturbing present arrangements of space in the ship, and a due regard to venerated pre- judices, which we have seen created during a single generation, and which have in that time erected the crude suggestion of Booth, successful though it has been made by others, almost into the position of an institution, the obvious course is to improve the fur- naces, shorten and widen the tubes, and, when draft is deficient, apply the exhausting fan with a short funnel. Although we do not insist so strongly on the last item, it may be observed in passing, that it would make " smoke burning" with economy in steam ships possible ; at present it is not. (See Chap, ii.) Should a radical reform of the marine boiler be aimed at, and we have never ceased strenuously to IN MARINE BOILERS. 31 urge its necessity, whoever attempts it must not stick at trifles. The Jboilers, in the first place, ought not to be " crushed down" to the bottom of the ship, where the draft has such difficulty to descend down after them. We would, in fact, abolish the stoke- hole, if not do away with the stokers, and stoking also. Instead of placing the fires so low down that, in a leaky ship they are soon drowned out, we would have them close up to the deck, in whatever situation the engines might be fixed. The "firing stage" should really be a platform elevated to the light of day, on which the most important processes in the economy and progress of a steam vessel is carried on, and to which the coals may be elevated, and, if re- quired placed in the furnaces also, by means of very simple self-acting mechanical appliances. In giving a reluctant assent to the proposition, let it not be forgotten by the reader, that this change of position in the boilers would really increase the available room for cargo, inasmuch as none would be wasted in pas- sages up and down for the hands, and for ventilation, to say nothing of the greater safety of the ship from fire; and though last, not least, when we think of the possible fate of the " President " or the " Pacific," from explosion. 32 ADVANTAGES OE A HIGH PRESSURE. In the case of vessels of war where the boilers, in this elevated position, might te obnoxious to the effects of shot, &c., the boilers may be retained in the usual position, and in such cases the room occupied by the stoking space is not so objectionable. Wrought iron boilers of simple forms, containing a steam pressure of 200 Ibs. per square inch, will be the most suitable in such cases. The communication of the boilers with each other, and with the cylinders may be easily arranged below the water level in the manner of the locomotive. The kind of boilers we propose for marine purposes, are not new schemes, but the inventions of practical men, matured by the experience afforded by extensive use. The principle is that of WOOLF where the pres- sure is exerted only within cylinders of comparatively small diameter, say up to 2^ or even 3 feet. The species of boiler made by Hall of Dartford, and others, known in London as the elephant boiler, may be ar- ranged to work at a pressure of 150 to 200 Ibs., and for low-pressure (say 80 to 100 Ibs.) when used in wooden vessels where internal furnaces are insisted on, we would recommend the modification patented by Galloway, of Manchester. The elephant boiler has been much used by the Trench, though but par- GALLOWAY'S CONICAL TUBE BOILER. 33 tially, perhaps, for steam navigation. Galloway's boiler has been used in this capacity, I believe, to some extent ; my own immediate experience with both has been principally confined to land. The latter boiler was first introduced into practice in London, and erected for public inspection and trial at the Great Exhibition in 1851. This boiler I shall now describe. THE GALLOWAY CONICAL TUBE BOILER. I use the term " conical/' rather than " patent/' in the designation of this boiler, because the pa- tentees have other patent boilers, also with vertical tubes, which tubes are not all conical, being partly "fire tubes" or, strictly speaking, small tubular flues, on the principle of the locomotive; and also to distinguish it in its most prominent feature, in relation to strength and durability, from the boilers of the American steamers "Pacific" and "Baltic/' Collins's line. The great and most important point of difference between the American and English boiler is, that in the former, the large internal fire- flue, or flame-chamber is occupied by a great number of parallel tubes, about 2 inches diameter, and 5 feet long, placed vertically, and connecting the upper and lower portions of the water chamber. Through these 34 GALLOWAY'S CONICAL TUBE BOILER. tubes the water, of course, circulates very rapidly, and there can be no doubt this arrangement forms a most effectual means of wanning a large quantity of water in a short time, and with great economy. Whereas in the Galloway boiler, the space behind the furnace is occupied by a smaller number of taper, or conical tubes of 5 or 6 inches in diameter at the lower, and nearly double that diameter at their upper ends ; consequently requiring more space in length of boiler, though less in depth, than the American plan, for the same quantity of heating surface. In a pamphlet written by Captain llamsay, R.IsT., published in 1851, entitled, " Eemarks on some of the causes that retard the progress of our STEAM NAVY/' several good observations are made in illustration of the necessity of using much higher steam than previously, in ships of war, and the diffi- culty in attaining that object with the ordinary construction of marine boiler, as well as on the ill- adaptation of that boiler with small tubes to the proper combustion of bituminous coal or other flaming fuel. In discussing this subject, Page 58, Captain Eamsay remarks, "The strongest form of boiler which we are ac- quainted with is one invented by Messrs. J. and W. GALLOWAY'S CONICAL TUBE BOILER. 35 Galloway of Manchester, and which, we believe, might, with modifications, be adapted to marine pur- poses. The peculiar principle of this boiler is the series of short vertical tubes which act as stays. The only objection to which these boilers are liable, as marine boilers, would be, that using water tubes, there is a liability to prime ; but we would meet that objection by making the upper part of the tubes very large in proportion to the lower parts." Now this last suggestion is a very important one, and had been previously made by the present writer, not with a view to prevent priming, solely, but also for insuring a more effective action of the flame against the sides of the tubes, as well as to prevent their being injured by overheating and burning out at their upper ends. In fact, I professionally advised the inventors, on being consulted by them, previously to taking out their patent for this water- tube boiler, in 1850, to adopt that course. This advice they followed, and have continued to pursue, with very great success ever since. Messrs. Galloway having supplied several 50 horse boilers, fortheGutta Percha Company's Works, City Road, and to several other factories in London, during that and the following year. 30 EVAPORATIVE POWER OF BOILERS. One of those boilers, erected under my superin- tendence, at the City Eoad Works is described and figured in my " Eudimentary Treatise on Steam Boilers/'' In that wort it was stated that this boiler was capable of evaporating a cubic foot of water per minute, with only about 6 Ibs. of bituminous coal per hour, not of the best quality, while driving a 30-horse non-condensing engine indicating 50-H.R, besides supplying steam for other purposes. This great, if not unprecedented, degree of economy has been doubted by some persons who have in vain tried to evaporate a cubic foot of water by less than 8 or 9 Ibs. under the same circumstances : that is, while driving an engine at full work, which is a very different thing to the kind of evaporating experi- ments some time ago carried on by order of Government, and published in sundry Eeports to Parliament on coals suited to the steam navy. These Eeports are merely an account of the results of cer- tain laboratory experiments, and, however valuable as scientific facts such investigations may be, it must be said that the labours of the eminent men engaged have been of little use in improving or illustrating the actual practice of engineers. The highest result obtained in these experiments was, 10*21 Ibs. of MODE OF DETERMINING EVAPORATION. 37 water evaporated from 212 for each Ib. of the best Welsh coal. (Ebbw Vale.) This result was obtained with a Cornish boiler. With a Galloway boiler, however, when new, with thinner tubes, that is, J inch instead of five-sixteenths, and welded up the side instead of being rivetted, I have, occasionally, obtained a larger performance than that given in the statement referred to. The result of the experiment in question was, that eleven and one-tenth pounds of water was evaporated by each Ib. of coal consumed of an inferior kind called East Adair's main. The pressure of the steam was carefully kept up during the experi- ment, (nearly 2 hours,) at exactly 40 Ibs. per square inch, the engine doing its ordinary work, except that the feed pump was stopped off, and, consequently, no feed-water was going into the boiler, which enabled me to measure very accurately the fall of the water- level in the glass water-gauge; and, knowing the exact internal dimensions of the boiler, the quantity of water boiled away was thus clearly ascertained with sufficient exactness for a short experiment : at any rate, the result was as near the truth as the quantity of coal used could be measured, considering that the quantity of fuel on the bars had to be esti- mated, to be equal at the beginning and the end of 38 WATER-METER TOR STEAM BOILERS. the experiment. At that time (1850) no such thing as an absolutely correct water-meter, at a moderate expense, for boilers, was in existence; that deside- ratum, however, now appears to be attained by the invention of Mr. Kennedy of Kilmarnock. So important an appendage to steam boilers as a correct boiler -meter, constantly registering the quantity of water boiled away, has been long looked for and longed for by every honest engineer. Besides being a continual check against that neglect of the feed- water which too frequently results in explosions, it will also be a serviceable check on the extravagant expectations often raised upon the statements of interested patentees of their schemes for saving fuel. I do not risk much in predicting that when these meters become more generally known and used, they will produce a revolution in the engine and boiler trade, quite as great as was produced by the first general introduction and improvement of Watf s indicator, by the late Mr. John M 'Naught of Glas- gow ; an era which makes us now look back to those times of hemp-packed pistons, " never tight," and air-pump buckets " never meant to draw," as to a long-bygone age, though but few years have elapsed since that barbarous time. And now, by the help of TEST OF SMOKE-BURNING PROJECTS. 39 the boiler-meter, we hope soon to dispel the present uncertainties of some hundreds of smoke patentees as to whether their plans save seven per cent, of fuel, or seventy, although, for aught they know, they are just as likely to do one as the other ; but I have a strong suspicion that the best of them, and I am far from denying that there are many good ones, will be found to come nearer two per cent, than twenty.* * Except, perhaps, 20 per cent, below par, negative " saving." But we trust this subject will yet receive, as it deserves, more serious treatment. At a meeting of smoke patentees, called by the authorities of Leeds, some years ago, one, the most notorious of them, whom we will call No. 1, promised 50 per cent, saving in fuel. No. 2, equally well known, promised 60 ! while others promised 70 and 80 ! ! not being particular to a few per cents., whom we may call, collectively, No. 3. The results are, No. 1 sent a new steam ship to sea with his plan, which ship very narrowly escaped the fate of "the President," being, only through the greatest care and discretion of her commander, brought back to Cork, to repair her boilers, after being nine days out on her way to America. No. 2 had his plan in operation not far from the Manchester Exchange, which ended in a well-known terrible explosion, killing nine or ten people. While No. 3, an 80 per cent, man, has more recently had one of the most destructive explosions on record in Yorkshire. 40 EXPERIMENTS ON EVAPORATION. Eeverting to our evaporating experiment at the Gutta Percha Works ; the pressure being 40 Ibs., the temperature of the steam and, of course, the water also, was at about 288 Fahr. In order to compare with the ordinary practice, the evaporation of 11*1 to 1 must be reduced to what it would be were the boiler supplied at the ordinary standard temperature of 100, which, by the Admiralty rule for that purpose, assuming the latent heat of water at 1000 is as Mows : (1212 actual temp. 288 Q ) X 11-1 q . 2 ]h (1212 - standard temp. 100) = 1112 " water to one of coal. It is proper to state that the rate of combustion did not much exceed 10 Ibs. of coal per square foot of grate bar per hour, and that the experiments were repeated in the presence of several f competent wit- nesses, occasionally reaching a corrected evaporation of 10 Jibs, of water to 1 Ib. of coal; or, in other words, a Galloway boiler made a common variety of bituminous Newcastle coal, in ordinary practice, go as far as the best Welch in a pet experiment with the far-famed Cornish boiler.1 In order to arrive at the best proportions to be PROPORTIONS OF THE BOILER. 41 observed in a boiler of this kind, we have ample experience to rely upon. Besides the experience afforded by the great number made by Messrs. Gal- loway, both for land and steamboat purposes during the last three or four years there is a sufficient number of them in the metropolis for the purpose of illustration. The dimensions of the boiler at the Gutta Percha Works, above referred to, where the evaporation experiments were made, are as follows : Length of boiler 30 feet 3 inches. Diameter of ditto inside, seven feet. Greatest diameter of main flue, 4 feet 6 inches inside, by 3 feet deep, con- taining 13 conical water tubes, each 11 inches inside diameter at top, and 9 inches at bottom, which tubes act as prop stays between the flat top and bottom of this main flue. The entrance to this main flue is by two parallel and similar furnace tubes, each 8 feet long, and somewhat oval in section, being 2 feet 6 inches wide, by 2 feet 9 inches deep* But they are stronger than if they were circular, on account of containing three strong cast iron bearing bars for supporting the grate, which act as prop stays from side to side. The fire-grates are each 7 feet 4 inches long, by 2 feet 6 inches wide, containing about | square foot of fire bar area per horse power for the 42 PROPORTIONS OF THE FIRE GRATE. 50-horse boiler. Each of the furnaces contained two lengths of fire-bars, the front bars being 1 inch, and those at the back 1J thick with f -inch spaces between them in both cases. This pitch of the bars was adopted without my concurrence, other- wise I should have preferred the front bars -inch thick, with the same spaces, and the back bars with J or five-sixteenth spaces, instead of f , in order to attain a more perfect combustion of the smoke ; that being the object for which Messrs. Galloway ori- ginally adopted the double furnace plan. These grates have since been replaced by Miller's (now expired) patent moveable bars as improved by Mr. Annan for Mr. Chanter, the proprietor of that patent, that is by making every alternate bar, only, moveable by hand, instead of the whole set, when each adjoin- ing bar moved alternately in opposite directions, according to the mode originally patented by Mr. Miller; These moveable bars, in some measure, answer the same end as the thin bars; that is, of increasing the rate of combustion and, of course, increasing the evaporating power of the boiler, at the expense, perhaps, of a little smoke, which, however, may consist with the most perfectly attainable econo- mical combustion of the fuel. JARGON OF SMOKE PATENTEES. 43 " Perfect combustion/' and the action of a " per- fectly smokeless furnace/' are very far from being synonymous, or even similar phenomena, and produce very different, and, sometimes, widely opposite results, both chemical and physical, not always likely to be recognised by every noisy patentee or pretender who takes his chemistry like his physic, from the pharma- copoeia. In some conspicuous instances, at least, the philosophical jargon employed really encumbers the path of science and progress and, finally, becomes a much greater nuisance than the smoke which these mock-philosophers pretend to subdue. So far from perfect combustion, and perfect smoke- lessness, in a steam-engine furnace being identical, they are, very commonly, the antithesis of each other; perfect combustion being the most completely effected when the whole of the oxygen passing through the grate, is the most nearly or perfectly used up in com- bining with the hydrogen and carbon of the fuel, although it may be occasionally accompanied by the inappreciably small loss of a few uncombined atoms of the latter substance in the form of smoke or soot, which in fact it is, in a finely divided and impalpable state, merely giving a black colour to the nitrogen and other useless incombustible gaseous products of 44 STRENGTH OF GALLOWAY* S BOILERS, the furnace. These products must pass off, visible or invisible, at whatever cost, although we question, were it possible to collect all the fuel in a large volume of visible snioke many hundreds of miles in extent, whether it would amount to a single ton of coals. A smokeless furnace, however, on the other hand, when the result of a thick fire, thick bars, and slow combustion may, and frequently does, occasion a loss of a large part of the carbon of the coal, which passes off by the chimney, only half-burned, in the shape of perfectly invisible carbonic-oxide-gas, thus creating a dead loss of 25 per cent, in coal. This evil, however, admits of prevention in these double furnaces, and by other simple means, As to the strength of this boiler, the furnace-plates are of Low Moor iron, f-inch thick, the flue and shell, of the same thickness $ the best Staffordshire, and the flat ends, -^inch* The ordinary working pressure of the steam being about 35 Ib. per square inch, gives a strain of about 4000 Ib. on each square inch sectional area of the iron in the circular part of the shell, leaving a surplus of about lOOOlbs. per square inch greater strength in that part of the boiler, which is equal to withstand a higher pressure of steam by 25 per cent., and we may be still assured that SUITABLE FOE HIGH-PRESSURE STEAM. 45 the boiler is not strained to one sixth of its ulti- mate power of elasticity, that being taken at about 20,000 Ibs. per square inch of sectional area. One object of adducing this case of a Galloway boiler at such length is to show the propriety of using a much higher pressure of steam than has hitherto been usual, or much practised in marine boilers, as well as the safety of those boilers for that purpose, and it is proper to state that the strength of the plates as above given is now found, after a trial of five years, constant work, amply sufficient for every purpose, with engines requiring steam from 40 to 50 Ibs. pressure. This boiler has been, during that time, which may be said to be nearly equal to 10 years' working the ordinary day work in a regular factory, and under the various vicissitudes commonly atten- dant on night and day working, it has not sustained a single casualty, and not even a leakage of any kind that could be discovered after the most careful in- spection. My own personal examination was parti- cularly and frequently directed to the upper end of the vertical tubes where the flame impinges with its greatest intensity immediately after passing over the furnace bridge. This particular part having been pronounced by all practical boiler makers as being 46 STRENGTH OF GALLOWAY^S BOILERS. the most vulnerable point in other vertical tube boil- ers. I, in consequence, subjected it from time to time to the most scrupulous examination ; the result on the whole has been so satisfactory that I now ven- ture to recommend this plan of boiler as pre-eminently suited to marine purposes. Should any doubt remain on the mind of any engineer as to the power of the " elliptical" flue, as it has been wrongly called, to re- sist collapse from 150 Ib. pressure, that doubt can only apply to the segmental or semicircular portion of its sides, the flat top, supported by any adequate number of tubes being impossible of collapse ; there is one exception which may be stated in order to re- move such doubt. And as exceptions sometimes prove the rule, this one will serve to corroborate our opinion, already expressed, as to the much greater strength of this form of boiler than those of the "Pacific," " Baltic," and others with longer vertical water tubes, and which therefore have the sides of their main flues, of greater depth, and consequently weaker. The exception is, that only a single case has occurred in the whole range of Messrs. Galloway's extensive practice in the manufacture of those boilers, where collapse in the flue took place, and on that occasion, as appeared from the report of another engineer, was OTHER EXAMPLES OF BOILERS. 47 clearly attributable to this portion of the flue having (from some unaccountable caprice) been made nearly flat, or at least with a very great radius of curvature. The proper curve, however, for this portion of the flue it is very clear should be a semi-cylinder, or a portion of one, of the same radius as the top of the furnace tube, when of the same thickness, they being both subjected to the same pressure. Besides other and larger boilers on the Galloway plan at the Gutta Percha works, I have also erected several of various sizes at other places, in which per- haps better proportions were attained. Two such boilers have been working for nearly four years past at the London Zinc Mills more success- fully perhaps, and with greater economy than has ever before been obtained with any other description of boiler, under similarly unfavourable circumstances. The dimensions of these two boilers are precisely the same, and are as follows : Length, 24 feet ; Dia- meter, 7 feet. Greatest diameter of main flue, 5 feet 7 inches, which flue contains 21 vertical water tubes, 11 J in. diameter at top, 6 in. at bottom, and 2 feet 10 in. long. These tubes are three-sixteenths thick, welded, and placed zigzag fashion, so that a man may creep easily along each side of the flue, and sweep in 48 DESCRIPTION OF MODE OF SETTING. amongst them. The boilers are placed upon a num- ber of fire brick blocks, or short columns, 18 inches high, 9 inches diameter, and 18 inches apart, so that the whole of the lower half of the external shell of the boiler, except where it rests on the columns is exposed to the smoke and hot air in the flame bed. The flame and smoke thus pass through among these columns immediately after passing through the main internal flue tube, and then dip underneath the ash pit, in order to pass into the chimney flue. Conse- quently the products of combustion, after proceeding from the furnaces, make but one return to the front of the boiler before passing off to the chimney, which happens to be situated near the front end of the boiler. The fact of the very great economy of these two boilers with this mode of setting, so very opposite to the Cornish, and indeed the too usual system of several returns of long winding flues, to which system it is in my mind utter condemnation, would justify any one, cognisant of this case, to set up such boilers in the direct manner, or without any return flues whatever. This circumstance shows the suitability of these boilers for marine purposes where no external flues can be admitted. The 4 furnaces of these 2 boilers are each 7 feet STRUCTURAL DETAILS OF BOILER. 49 6 inches long, by 2 feet 9 inches diameter, and 2 feet 11 inches deep, composed of Low Moor plates five- sixteenths thick. Each of these furnaces contained 3 lengths of fire bars, each about 2 feet 2 inches long, % inch thick, and f inch spaces between them, making about f of a square foot area of fire bar sur- face for each nominal horse power of the boiler, that being called 55 horse. The external circular shell of the boiler is f inch thick, and the ends seven- sixteenths of Stafford- shire plates, " Thorney croft's best best crown iron." The flat ends are stiffened by angle irons riveted across from side to side, midway between the flue and the top, and from these proceed stay bars 6 feet long, riveted in a sloping direction to the top of the boiler. Besides these, each end is further strengthened by 4 " gussett " or angular plate stays. The angle irons round the ends are 3| inches broad, and the rivets are 2 inches pitch. Each boiler is surmounted by a cylindrical horizontal steam " dome" 10 feet by 3 feet, with curved ends, the same thickness of iron as the boiler. This dome is riveted to the boiler by 2 cast iron necks, or short pipes 10 inches long by 8 inches diameter. To these domes the steam pipes are attached. One 5 inches flat disk lever safety valve ; and one E 50 BOILERS OF ROLLING MILLS. glass water gauge is attached to each boiler, but no float gauge nor self acting feed. These two boilers were employed to drive two 40 horse engines of the ordinary Boulton & Wattf s construction, made by Peel, Williams, and Peel, of Manchester; 34 inch cylinders, 6 feet stroke, and 20 turns a minute, working together a little over 200 indicated horse power, which they ordinarily did with less than 3 Ibs. of coal per horse power per hour. The steam, being 35 to 45 Ibs. in the boilers, is cut off by the governor and double beat throttle valve instead of a separate expansion valve, at an average of about \ to \ the stroke. It is perhaps useful to mention that the peculiarly sudden action of this double beat or equilibrium valve, when used as a throttle valve, has always a tendency to cause priming, much more than the ordinary spindle throttle valve of Boulton and Watt. This, together with the nature of the work carried on, that of rolling thick lumps of metal, called signifi- cantly enough "breaking down," and thin sheets called " finishing," where very great irregularity of resistance is inevitable, involves the necessity of keeping the steam very much higher in the boiler than is required in the cylinder ; the steam in the 1 CONDITIONS UNFAVOURABLE TO ECONOMY. 51 cylinder seldom ranging so high as 20 Ibs. per square inch, while in the boiler it is from 30 to 40 Ibs. The ever varying resistance caused by these lumps and sheets of metal passing through two, three, or four pair of rolls, at the same time, is one of the unfa- vourable circumstances for economy before alluded to. Another circumstance, unfavourable to very great economy in this case, was the draught, which, although the chimney is of sufficient elevation and capacity, was much injured by communication with other furnaces and fire-places, some of them open ones, which, without great care in, or total absence of stoking or stirring the fire, made it impossible to pre- vent some smoke at particular times, especially after the fire doors had been thrown open, and the furnace too much cooled. Although valves were applied for admitting air at the bridges of the four furnaces of these boilers, by which all dense smoke was thereby entirely prevented for a period of three or four months, and a certificate was obtained from Sir Eichard Mayne, the chief inspector under the Metropolitan Smoke Act, to that effect. Yet no sooner was there an occasion to change the fireman, for a more indus- trious stoker, than the smoke again appeared, and the owner was convicted, unjustly, as I think, in a 52 CONDITIONS UNFAVOURABLE TO ECONOMY. penalty under Lord Palmerston's Act. It is unneces- sary to add that the greatest economy of these boilers in fuel was before the Smoke Act came into operation. In addition to this,, the situation of the boilers was such as necessitated the " dipping" of the flue con- siderably,, in order to enable it to pass beneath the ash pit, which is well known to be extremely detri- mental to draught. Notwithstanding all those draw- backs against the probability of a good performance with,, at that time, nearly a quite new kind of boiler, these boilers have continued to work four years without mishap or difficulty of any kind nearly two years of that time night and day at the same extremely econo- mical rate. More practical reasons of the like kind might be here given; but what has been already advanced may be considered sufficient to warrant the conclusion that this plan of boiler might at once be applied as a marine boiler, with the greatest propriety and moral certainty of success. For this purpose the boiler will require very little modification from the form indicated by the above description. If any deviation be neces- sary, I would advise that for 60 or 70 Ibs. pressure the diameter should be reduced to between 5^ and 6^ feet, and to meet the exigencies of working with salt BOILERS AT GEEAT EXHIBITION. 53 water, besides using the ordinary surface " blow off," and other similar appliances,"* we would make all the plates one- sixteenth inch thicker throughout. If required to work nearly or quite up to the maximum pressure of 100 Ibs., then all the parts admitting of it should be double riveted, and the rest welded. THE EXHIBITION BOILEB, OF 1851. Ill recommending that the diameter of a high pressure Galloway Boiler should be about 6 feet, it is not without due consideration, and considerable ex- perience of various precedents that I offer this recom- mendation. One such boiler may now be referred to, belonging to the West-Ham Gutta Percha Co. of West Street, Smithfield, by whom it was bought of the Commissioners of the Hyde Park Exhibition of 1851, where it had been worked during the 6 months * Lamb's " Surface blow-off apparatus," as described in Murray on " Marine Engines," 1852, or my Boiler Cleaning Machine, as described in my Essay on Boilers in 1838, and first figured L in the Artisan Club's " Treatise on the Steam Engine," in 1844, may be used indifferently as they are substantially the same thing intended for different purposes ; the object of the former being to prevent scale, and that of the latter to prevent priming. 54 BOILERS AT GREAT EXHIBITION. that the Exhibition was open. And, although only one of nine boilers of about equal power used for the purpose, it supplied as nearly as could be estimated, about one third of the whole of the steam used in that building. To young engineers, who usually take theory before practice, it may be as well to state that my reasons, when consulted on the subject, for fixing on 6 feet as the most fitting diameter for this Exhibi- tion Boiler, were, in the first place, that with that diameter, according to the rules already given by me, a f inch plate is of ample strength for a working pressure of 40 Ibs. per square inch ; that being the steam pressure recommended by Sir W. Cubitt, and the other Commissioners, not to be exceeded, and from whom I obtained at last, with some little perseverance, their consent to exhibit this boiler, a difficulty created through some mistake, by which four boilers of a diffe- rent kind had been previously ordered. It was then erroneously supposed that those 4 boilers which were of the multitubular class, though without fire boxes, blast pipes, or large chimney for draught, would have furnished an ample supply of steam for all the pur- poses of the exhibition ; but in this power, as the event proved, they were utterly deficient, not producing even half the quantity of steam required, so that this BOILERS AT GREAT EXHIBITION. 55 Galloway Boiler was considered only as a supernu- merary one a circumstance which gave a very instruc- tive lesson to the railway and other engineers who had the principal share in managing the preparations for working the machinery on that occasion ; and the result was thai four additional boilers had to be supplied in great haste by the same contractor, making in all eight of the multitubular variety, and one Galloway Boiler, before an adequate supply of steam was obtained. Although had the architectural and deco- rative portion of the Commissioners consented to the erection of a brick chimney, which would have been quite in keeping with the engineering and scientific object of the Exhibition, instead of nine boilers, any three of them would have been sufficient, besides giving an excellent opportunity of exhibiting a variety of smoke-burning inventions which were thereby virtually ignored. As it was, there was a petty exhibition of locomotive chimneys, a few feet in height with one exception, the funnel of a marine boiler, only 20 feet high, which in spite of some opposition I succeeded in having erected to the Gallo- way Boiler we are now describing. The pressure of the steam being limited to 40 Ibs. per square inch, a f -inch plate will only have a ten- 56 BOILEES AT GEE AT EXHIBITION. sile strain upon it of something less than 4000 Ibs. per square inch, sectional area of the iron. The formula for the strength of boilers winch I usually. is 2 st employ , jp=- - where s is the strain which, in Cv this case=4000 Ibs., =the thickness of the metal in inches,=*375 or f , and <^=the diameter of the boiler, 72 inches, or, - will be the pressure of the steam allowable Avith these dimensions ; and I have no doubt whatever that double that pressure might have been put on with perfect safety, so far as the tensile strain on the circular portion of the boiler is concerned. Another reason for the particular dimensions of this boiler was, that, besides knowing well what a f plate will bear, it is so very much used that the pro- per thickness for securing the best workmanship can readily be obtained. There needs, perhaps, no excuse for having made this boiler "stronger than strong enough," seeing that it was to be erected in the close vicinity of so many thousands of persons, daily assembled in the Exhibition building, which was, of itself, a matter of no little RELATIONS OF STRENGTH AND QUALITY. 57 responsibility, for it was considered good policy not only to be perfectly safe, but also to enable the general public to feel themselves safe, by an assurance of a surplus of strength so far beyond any possible requirements. Por ordinary commercial purposes, however, where people generally know what they are about, as well as for warlike and other government purposes, where they ought to know, if any where, this very inordinate precaution is out of place. And although I have, both by precept and example, recommended, in common with many other engineers, 4000 Ibs. for "best" Staffordshire, and 50001bs. per square inch strain for Yorkshire iron, as a safe rule to be adhered to by boiler-makers ; I am now inclined to modify that opinion. By fixing too low a standard for strength of iron structures generally, the result has been to induce the manufacture of very inferior and low-priced qualities of iron, which are substituted for the best in many situations where detection of the inferior quality is difficult ; and, so long as such infe- rior qualities reached the low standard required for the best, at a much higher price, an inducement is gradually being created among boiler-makers to believe that, in many instances it is only " the name 58 RELATIONS OF STRENGTH AND QUALITY. of the thing," which their customers are desirous of paying for. Hence the various designations of " best " and " best best iron," although the latter, in some cases, signifies the worst of two or three qualities made at the same place. As f of an inch is a kind of standard thickness to refer to, and the kind called " Thorney croft's best crown " is so well known, it is proper to state that, not only has the boiler already referred to been working at from 50 to 60 Ibs., but several other boilers of the same kind of iron, same thickness, made by the same makers, and in every way similar, except in being 1 foot more in diameter, (which would be equivalent to an increase up to from 60 to 70 Ibs. upon this 6-foot boiler,) have been working nearly the same length of time, and they are working now with perfect impunity, at the same pressure. Those boilers were all tested at the injudicious pressure, in my opinion, of " three times their working pressure" There is an universal prejudice among engineers in favour of this "treble proof" of the strength of a boiler. This Exhibition boiler, for instance, was thus proved, in the presence of one of the Eoyal Commissioners, at 150 Ibs. per square inch, which pressure, in the Commissioner's and the maker's RELATIONS OF STRENGTH AND QUALITY. 59 opinions, was required to justify them in working it at 50 Ibs., although, in an ordinary case, 120 Ibs. would have satisfied them when the working pressure was intended to be only 40 Ibs. Now I am not going to contend that the least injury was likely to be sustained by this particular boiler exposed to so severe a strain; but I wish to point out the absur- dity and injurious consequences likely to arise from the prevalence of such a dogma when applied to very high pressures, however safe it has always been at low ones, say under 10 Ibs., or, at most, up to 20 Ibs. per square inch. If, instead of moderately good Staffordshire plates, capable, we may suppose, of bearing a tensile strain of 20 tons per square inch section before breaking, we have a boiler to test made of an inferior quality of iron, say only capable of supporting 16 or 17 tons, which was found by Mr. Lloyd to be the ultimate strength of the iron of the boiler of the " Cricket " steamboat that exploded on the Thames, in 1847 ; and if as was proved by Mr. Lloyd, in that case, by direct experiment on the corresponding boiler, every way similar to the exploded one, namely 5 feet diameter and | -plates, that the latter was severely strained close to the bursting point, and permanently injured 60 BOILER OF THE STEAMER "CRICKET." by the application of 1361bs. per square inch, giving a reduction of about 40 per cent, for the riveted, below the original, or solid plate, as tested by him, in strips of 2 inches broad. We have only to suppose that our Exhibition boiler had been of the " halfpenny boat Cricket" quality, and if tested at three times the intended pressure, or 120 Ibs., which it might have passed safely, perhaps, once, and after- wards worked, without suspicion, at 40 Ibs., although in reality, weakened by the process so much as to become dangerous, even at 60, and it might explode at half-a-dozen or so pounds higher pressure. If such a result may follow such a practice, what, it may be asked, would be a safer mode of proceeding ? I answer, from the results of my own practice, as follows ; I would have taken a mean point in the above supposed case, between 40 Ibs., the working pressure, and the estimated strength of the iron, say 140, which would be at 90 Ibs., and make that the point at which to test the boiler. That is not much more than double, in fact, 120 per cent., above its working pressure, namely 50 Ibs., as well as being also 50 Ibs. below the estimated strength of the iron; and supposing the life (as it is called) of such a boiler to be estimated at 5 years, then this proof test ought BOILER OF THE STEAMER "CRICKET." 61 to be reduced by equal instalments of 10 or 15 Ibs. each year. Now who will say that, if such a course of procedure, or some similar one, had been made compulsory by legal enactment, before the " Cricket " explosion, that that "accident," and many others, would not have been avoided ? But as we are, so far, only dealing with probabilities, we may take the actual pressures used in the " Cricket," namely, working pressure, as proved at the inquest, 66 Ibs., the bursting pressure, as proved by Mr. Loyd's -j O f* I f f* experiments, 136 Ibs., which gives a mean of & =101 Ibs. for the testing point, or about 50 per cent, only, above the actual working pressure. By this, it will be seen how much safer a test of this proportion would have been, than the treble test. I have stated in a previous work, that a test of double the working pressure was amply sufficient, but I by no means wished it to be inferred that such a test should be considered to be necessary, or useful, except at moderately low pressures. In my notes to the edition of " Tredgold on the Steam-engine," pub- lished in 1852-3, I regret having overlooked what I consider a dangerous error in that author, although he admits that double the working pressure is a suffi- 62 FALLACIES IN TEEDGOW/S WORK cient test for low pressure boilers, lie states that " it becomes insufficient in high pressure boilers, because they have a smaller amount of steam room," and actually gives a formula for calculating the excess of strength which he would give to a boiler on that account, saying, " If one boiler contains 20 cubic feet for each horse-power, and another only 10, the boiler with only ten feet of space should be of twice the strength." It is scarcely necessary to point out how TBEDGOLD confounds, here, two entirely different objects ; one, the prevention of injury to boilers by excessive strain in testing them ; the other, the hav- ing such an excess of strength as " to provide against accident in the event of the valves being out of order," &c. (Page 268.) Trusting that these remarks may, in some small degree atone for the share I took with others much more competent, in delaying a little longer the descent into oblivion of this heterogeneous work of "Tredgold on the Steam-engine," I shall return to the description of the Galloway Exhibition boiler. If as I think I have made manifest, this 6 feet boiler of f Staffordshire iron, with the ordinary lap and single-riveted, be equal to a working pressure of 70 Ibs. per square inch, then it may safely be asserted ON THE STEAM ENGINE. 63 tliat a boiler of the same shape and dimensions of Low Moor or Bowling Iron, one-sixteenth of an inch thicker, and double-riveted, welded indeed where necessary, and judiciously stayed, would be abun- dantly safe to work in a steam ship at the maximum pressure of 100 Ibs. That such a boiler for such a purpose would be very decidedly superior in every respect to any form of marine boiler at present in ordinary use for large steam ships, scarcely admits of a question with any one understanding the subject; and those who do not may have the clearest of proofs in the performance of the land boilers I have referred to, as well as that of many others on the same principle, now spread all over the country. We contend for the adoption of the correct principle which we know that these boilers con- tain. And as certainly as is the truth of any common rule in arithmetic demonstrable to those who consent to examine the proof, so certain is it in my apprehension that any expedient, which supersedes the present flue and multitubular marine boilers, will very considerably accelerate the passage between this country and America. If this be accomplished even only by a single day of the nine that is yet required, a 64 IMPORTANCE OF IMPROVED BOILERS. great object will be attained for the progress and wel- fare of the people of both countries. That such an achievement is a point worthy of any man's ambition, we need not insist on or that of any number of men, on either or on both sides of the Atlantic. To shorten the way to America, by reducing the time now occu- pied at the rate of only 10 per cent, per annum for the next 4 years, would solve a problem of immense social importance. It would in four years time lay us along- side our friends and brothers in the United States in six DAYS ! That this will yet be accomplished, there can be little doubt ! Experiments in fact are already in progress with this end in view. To reach New York in six days is an object far above any partisan or even national views, nor is the benefit wholly measurable by the pecuniary or commercial advantages attained. For it is by such achievements that nation is to be knit to nation by bonds of undying brother- hood, and the advent is to be hastened of that peace- ful kingdom, the clarion of whose renown, and the majesty of whose sceptre, will command the joyful homage of mankind. On a subject of such vast interest as a material im- provement in the art of steam navigation, every engineer, sailor, and shipwright, has some crotchet AND FIRE-FEEDING MACHINERY^ 65 of his own. I confess not to be singular in this re- spect, and -some of my plans of improvement have been not confined to paper. They have embraced both engines and propellers, but have principally been devoted to boilers and to furnaces. Though certainly I have never been guilty of trying to help a ship on her way to America by burning smoke, the miscarriage caused by which was subsequently visited upon un- offending parties. The merit of that abortive attempt lies with Mr. Charles Wye Williams, so well known for his nostrums in smoke prevention, and the untiring energy, usually appertaining to such adventurers. That a properly constructed Fire-feeder, which would supply the furnaces without involving the necessity of opening the fire doors, or admitting air except through the fire bars, would be of great advantage, and abolish the slavery of the stoke-hole, no one can deny. But that would be irrespective of any smoke- consuming or preventive properties it might possess ; which, however desirable should not be allowed to engross our first attention. Feeding and stoking the fire, however, have long been accomplished by very simple machinery, on the principles of Stanley and Walmsley, and Miller. All the three inventions are now public pro- F 66 EXHIBITION BOILER perty ; the patents having long since expired ; and, alas, the patentees, whom I knew well, have ex- pired also. They were thoroughly practical engineers, and their inventions were entirely successful on land, as they would have been on sea also had an oppor- tunity been afforded for their trial. Those appliances to a suitably constructed marine boiler it is under- rating them to say would increase the boiler power of the steam ship by 10 per cent., as they have always done that of the steam mill on land by double that amount. These, and many such equally valuable inventions, not the speculations of mere " science-mongering " amateurs, or paper engineers, but the actual tried and proved productions of practical operative mecha- nics, lie at hand ready for application to every emer- gency that can possibly arise in the development of that improvement of steam navigation now so urgently required. "Where there is a will there is a way," is an axiom in mechanics, as in other things, if there be money. As a sample of the mode of proceeding in the choice of an improved boiler, let any plain busi- ness man or merchant, he need be neither an engineer nor man of science, obtain a ten minutes interview with IN SITITKFIELD. 67 the manager of tlie West-Ham Gutta Percha Com- pany, at their extensive works in West Street, Smith- field; or let him go to any other factory of which there are several in London, where the Galloway Boilers have been working for several years ; for, I perhaps take a liberty in referring to this one more than others, which I have done from its central position in the city, and its having been so well known for many years as the Iron Works of the late Alexander Gallo- way and Sons, the eminent engineers, formerly of this country, but now of Egypt. He will there see the original Exhibition Boiler at work, which, I have the authority of Mr. Walter Hancock, of the Gutta Percha Company for stating, has been working under his superintendence almost uninterruptedly four or five years since the closing of the Exhibition a great portion of that time working night and day, and fre- quently at the extreme range of pressure; this too without any deterioration from use. A few minutes' inspection will bring entire conviction of the accuracy of what we state. The visitor will there see a greater quantity of steam produced by a comparatively small boiler, which might if necessary be fixed aboard a steam ship, and at work in a few days, at a greater pressure by two or three times over than is now 68 GOOD BOILERS EASILY MANAGED. generally attainable in the present marine boilers. Withal, too, at the cost of a much less quantity of very inferior coal than is at present required perhaps by any other description of boiler, even on land. He will see all this done without the fussing, stewing, and sweating of the present barbarous stoke-hole prac- tice aboard ship, which too many people think a necessary concomitant of all marine steam engines. On the contrary, he will see the work done quietly, with cleanliness and easily; and the black smoke "perfectly consumed" into the bargain, without the intervention of any smoke consuming apparatus of any kind, patent or otherwise; no air being admitted to the furnace except what passes through the fire grate ; and he will instantly ask himself, is all this applicable or possible in a steam ship ? My answer to such a question is, that it certainly is, excepting merely the tall brick chimney, the want of which would only affect the ability to consume inferior fuel, or the prevention of a little smoke, but which quali- ties, if thought important, may be easily retained by the introduction of a small blowing fan. VALUE OF BRICK FIKE-PLACES. 69 THE ELEPHANT BOILER. Having disposed of the question, how steam can be best obtained at a pressure, or nearly up to a pressure of 100 Ibs. per square inch, and that in boilers with internal furnaces, thereby permitting their use in wooden ships where necessary, we come now to the requirements of 100 Ibs. pressure and upwards. For this purpose we anticipate the neces- sity of an iron ship. The reason for this is, in the first place, that to enable boilers, of a given thickness and strength of material, to stand a double pressure ; they must be just half the diameter therefore it is necessary to have external instead of internal furnaces. It is an inevitable law that the strength of the shell of a cylindrical boiler is inversely as its diameter ; or in other words, if we find a 6 foot diameter boiler with a | shell to stand 60 Ibs. pressure, then we may be assured that a 3 foot boiler will stand 120 Ibs. pressure, or nearly so, under the same circumstances. In the second place, the full value in heat, from any kind of fuel, cannot be obtained without the inter- vention of fire brick, or other non-conducting sub- stances, but with which it would be quite impracti- cable to line the present marine boiler furnaces ; or in 70 ELEPHANT BOILER SUITABLE fact almost any internal furnace for commercial pur- poses, although we recollect the case of an iron fire box boiler, erected to heat a new church in Man- chester some years ago, having its steam-genera- ting power nearly doubled by simply putting in a fire-brick lining round the fire grate ; thus prevent- ing the refrigerating effect on the fuel and flame pro- duced by the close contact of the water- casing and bridge of the fire-box. Many good smoke burners have been made simply by inserting a few fire-bricks in this way thus as it is called concentrating the heat. By making a small boiler, we make a strong boiler ; and by making a brick furnace, we make a hot fire. In adopting the elephant principle for a marine boiler, we get both these advantages, a small diameter and an external furnace ; but, besides that, we get a large width of fire-grate, and the convenience of using firing machines. Moreover, as the resistance is more dependent on the width of the ship than its length, it is incumbent to occupy the entire beam dimensions of the vessel without the intervention of water-legs between the furnaces, if we require the maximum power of the boilers, when they are arranged transversely across the ship. This the elephant boiler FOE MARINE PURPOSES. 71 gives us the means of doing with advantage. A range of 3 or 4 boilers may be thus made to occupy the whole breadth of the vessel, with nothing beyond a thin fire-brick wall between the furnaces. The proper physical management of the furnaces is a matter on which far more reliance ought to be placed for increasing the power of steam ships than is dreamt of by any of our " chemically considered" combustion patentees. It is not undervaluing science, but the contrary, to maintain this; in which I shall be joined by Earaday, as I was by John Dalton, when living. To encourage a fireman to work by tact and judg- ment not by empirical rule, to become dextrous, watchful and discriminating, is surely of more use than to cram him with the jargon of science, which would leave him as useless a member of society as those who are already thus distinguished. Chemical diagrams, and the atomic system of philosophy, will give little aid in keeping up the steam, and those who are chemists among stokers, and only stokers among chemists, will lend little aid to the advancement of either art. Although the elephant boiler is, perhaps, more popular in France, and on the Continent, generally, where it was introduced by Woolf himself, many years 72 ELEPHANT BOILEE IN SPAIN ago, it is much, used in and about London, principally at flour-mills, being considered a strong and safe boiler, but smoky ; hence it is often used with Welsh smokeless coal, but it is well adapted to Jukes' s, Hall's, or other smokeless fire-feeding machines. I consider that three, instead of two lower tubes, are objectionable, as they are, in that case, too small to be easily kept clean. Such boilers are not much used in the manufacturing districts, where they are known as " French " boilers ; but there are some good examples in Lancashire, the two lower tubes being made large enough for a man to get into to clean. They have been commonly made by Messrs. B. Hick and Son of Bolton, to go with their engines abroad. Some erected by them at Barcelona, in Spain, were of well- considered proportions, being 24 feet long, the main body of the boiler 4 feet diameter, and egg-ended; the two lower tubes each 2 feet 2 inches diameter inside, with only two or three inches betwixt them ; the vertical connecting pipes, or water-legs, were 18 inches diameter, and the fire-grate was 5 feet wide by 6 feet long. The most powerful boilers of this kind I have seen were erected by the same makers, at the " India mill" of Lees, Kershaw, and Co., in Stockport. They are AND IN STOCKPOET. 73 35 feet long by 5 feet diameter in the main barrel, the 2 lower tubes are 2 feet 3 inches diameter, con- necting pipes 16 inches diameter, and 2 feet 3 inches high. The main barrel of the boiler is flat ended, and contains a fire-flue 2 feet 3 inches diameter, which is the most objectionable feature as regards safety. Nevertheless, these boilers are worked very satisfactorily with a pressure of 64 Ibs. per square inch, and using little more than 40 tons of coal per week. Two of them are capable of exerting about 500 indicated horse-power, driving cotton machinery, &c. They consume about 3 Ibs. of coal per indi- cated horse-power per hour, by means of a pair of compound engines of 8 feet stroke, making 16^ strokes per minute. One engine has the large cylinder 50 in. diameter, and the small one of 23 in. The other engine has the large cylinder of 52 in., and the small one of 2 5 in. The steam is cut off at 5f ft. of the stroke. These boilers occasionally work in conjunc- tion with double-flued cylinder or Cornish boilers 6 feet diameter, with which they contrast very favour- ably. The fire*bars are f -in. thick, and the rate of combustion quick, say 10 to 15 Ibs. of common coal per square foot per hour. The draught is produced . by a brick chimney, 65 yards high by ,6| feet wide 74 GREAT POWER, ECONOMY, AND inside, at top, and 1 inch per yard batter outside. The above data were collected in 1848-9, since which the boilers have been supplied, I believe, with my cleansing-machines, and with Dean's double fire- feeding machines ; they have also been covered with felt, &c. : all, of course, tending to produce a still more economical result. I offer this as a sample, and not by any means a solitary one, of the engineering economy of Lancashire, which I would submit to the consideration of my engineering friends in Cornwall, with their lightly loaded engines and superior coal. I scarcely need add, that none of the new smoke- burning schemes have any share in producing the economy at the India mill, unless Mr. Dean's excel- lent fire-feeders be classed among such. They, how- ever, do not operate by letting in cold air against the boiler bottom, but by keeping it as hot as possible, and the fire-door shut. At any rate, they cannot be said to be benefited by anything that has come out of Lord Pahnerston's Smoke Act. At another mill, belonging to the same firm in Stockport, previous to the erection of this one, having three large engines, also, doing about 500 horse-power by 120 tons of bad coal per week, several then well-known plans of smoke- consuming, or prevention, were tried succes- SMALL COST OF ELEPHANT BOILERS. 75 sively without any appreciable saving of coal ; some of them at an expense of some hundreds of pounds. The list of inventors\or patentees' names, as given to me by a member of the firm, comprised those of Rodda, the two Halls, Chanter, Armstrong, and "Williams. My own plan, in this selection, it is only proper to state, was the only one that cost them nothing, being a careful system of charging the fires at the back, which I introduced at the same works, the Mersey mills, then belonging to another firm, many years previously. This mode of firing is described in one of my " Tracts on Steam," also in the Artisan Club's Treatise on the Steam Engine. I might here ask what possible objection could be raised against taking so simple and efficient a boiler as above described, and of which the performance can be so easily verified, and place it in an iron steamer, at once, and withal at so cheap a rate, (from 35 to 40 per ton of Low Moor iron,) in place of the present multitubular marine boiler, costing double the expense ? In referring to Arthur Woolf as the inventor of boilers composed of systems of comparatively small water-tubes, and which he was mainly conducive to bring into use between 1810 and 1820, it is not to 76 DEMAND FOR WOOL/S BOILERS. be understood as applying exclusively to the parti- cular form of boiler patented by him. That boiler was, for reasons applicable to most patented articles, not the best specimen of the invention, and it was deficient in proper circulation of the water. Woolf s boilers were really not successful until they took the form of the Elephant, or French boiler, the latter designation being applied in consequence of its being first introduced, if not also first made, in France, by Mr. Woolf himself. I rather wish to consider him in common with Oliver Evans in America and Dr. Alban on the Conti- nent, as the propounder of a principle of construction of perfectly safe boilers for very high pressure, that of confining the pressure entirely within tubes of compa- ratively small diameter. That system of construction was almost a necessary concomitant of the intro- duction of the compound high and low pressure engines by Woolf and Edwards, which engines have been, since their time, extensively made by Hall, Humphreys, Eennie, Hick, and others. The great -success of these engines m. extreme economy of fuel with extreme high-pressure steam, has for some time past created a demand for suitable boilers ; and that 4emand has been recently met, in an excellent form DUNN'S PATENT EETOET BOILEE. 77 of boiler partly on Woolf's principle by Dunn, Hat- tersley, and Co., of Manchester. But in which, the circulation of the water is more perfect than in Woolf 's original plan. The patent boiler of this firm, termed by them " the Duplicate or Eetort boiler/' is represented in the annexed cut. FIG. i. It was first introduced to public notice at a meet- ing of the Institution of Mechanical Engineers at Manchester, and has since been tested to work with perfect safety at 250 Ibs. per square inch. One of the retorts, 19 inches diameter having been purposely 78 MUD COLLECTORS, WATER HEATERS, pressed until it burst, was found to sustain the extreme high pressure of 525 Ibs. before it gave way. This boiler appears to be formed principally with a view to portability and lightness, for convenient transit, in which it certainly exceeds all others. Besides its great strength, it has, in my. estimation, other valu- able features, such as its capability of admitting any modification in size of fire-grate, or of fire-feeding machinery, underneath it ; and next .to that is the very large proportion of effective heating surface exposed to the direct radiation of the fire on the grate. ,It has also the advantage of admitting of the retorts 'being turned over, as they become blistered or worn over the fire,, or of 'being replaced by others far- ther off, or by nWo^es. An attentive consideration' of Mr. Dunn's boiler will discover it to possess some valuable peculiarities in regard to the deposit of mud, which so long as the water chambers are connected, must necessarily lodge principally in a few of the retorts farthest from the fire-grate. The retort at the extreme end will in fact act as a mud vessel or cleaning apparatus for the remainder. A most important purpose will thus be effected, which I hope to have an early opportunity of comparing with previous inventions for the same AND BOILEll CLEANERS. 79 purpose before pronouncing a decided opinion. Content for the present in remarking that the same conditions which constitute the last retort of the series an effi- cient mud collector, also constitute it the most appro- priate portion of the boiler at which to supply the feed water, and thereby act as a heater to the latter. v To this portion of the boiler Mr. Dunn attaches a cock, or other means of blowing off the sediment frequently. Of mud collectors and water heaters combined there are a great many varieties, among which we may mention that of Mr. E. Green, of Wakefield, as one of the most successful in extensive use ; but I have never seen any that in simplicity and compactness ap- proaches this of Mr. Dunn's, and I would say it is applicable to other boilers, the Cornish in particular, as well as the retort boiler, of which it is a component part. Of cleaning machines that are applicable and effec- tual in every situation, to all qualities of water, and every kind of boiler, locomotive, stationary, and ma- rine, there is only one variety ; that with the internal collecting vessels, agitator, and blow-off cock, that can prevent priming. And this they do most effectually under all circumstances, if there be room in the boilers to fix them. Nothing can be of greater import- 80 GALLOWAY'S PATENT MARINE BOILER. ance in improving the steam engine than the effectual prevention of priming, and the snbject of cleaning machines is on that account alone almost entitled to some future volume of such a work as this to itself. I was not aware until after page 33 of this work was printed, that any of Messrs. Galloway's conical tube boilers had been tried in sea-going vessels, but learning the fact that some vessels had been re- cently out to Constantinople containing them, I im- mediately procured the above sketch from the patent office, which I am informed represents correctly the boilers in question, although not drawn to any precise scale. 81 CHAPTEE II. SMOKE PREVENTION AND ITS FALLACIES. WHILE the greatest attention has been given by engineers at all times in advancing the steam engine towards perfection, much less has been done than ought to have been done in improving the construc- tion of the boiler ; but least of all has been done for the furnace the details of fire-grate, the supply of fuel, and the most important of all, the management of the FIEE, upon the proper operation of which much of the efficiency of the machine is dependent. The business of the "stoker," however subordinate and apparently unimportant, cannot long be neglected with impunity; for, like the organ-blower, he will occasionally let us know that the instrument cannot work without him. That portion of mechanical engineering which concerns the architecture of fur- naces, has been for so long a period left to the mercy of the operative bricklayer and the ironfounder, who have 82 ADVERTISING QUACKS AND both done what they could with large quantities of ire-brick, fire-clay, and thick heavy fire-bars, that it has become, like certain less agreeable portions of another profession we might name, which the re- gular practitioner commonly endeavours to avoid, but which there are plenty of " irregulars " ready to occupy. The consequence of this has been, as in the profession alluded to, that this important branch of engineering is so much over-run by quacks and pre- tenders, as generally to excite a considerable degree of contempt in honourable minds for the section of the arts thus degraded. To these phenomena may now be added the natural effect of the recent alteration in the patent law, which has so suddenly overwhelmed the community with swarms of great and little mono- polists in every direction, and it is not the least part of the swarm which has settled down upon that oppro- brium of engineering, the smoke nuisance. On this subject every smatterer on science has a theory of his own to uphold. Nearly every ironmonger is now a patent-furnace monger, and any gas-fitter is ready to fit us with his patent apparatus for "consuming smoke." Advertising quacks, whose business is puffing, are ready to subdue smoke puffs, and promise at the rate of 20, 30, and 40, or any other per THEIR FALLACIOUS PROMISES. 83 centage, in saving of fuel, by adopting their several nostrums, each guaranteed by hundreds of cut-aiid- dried testimonials. Audacity in this matter is far from being confined to the needy pretender, but stands out boldly bedizened in the canonicals of science. The style adopted, and the expedients resorted to by these smoke doctors, are worthy of Dr. Solomon, of Balm of Gilead notoriety, or of any other of that band of patriots who request us to beware of counterfeits. The policy pursued is that of continual reiteration to induce a belief of incredible statements, or to create faith in such respectability as at least possession of money may give. This we see daily in glaring signboard announcements. Indeed some of the most conspicuous and wealthy of those worthies are known to have competed at public meet- ings in the provinces, in extravagance of pretension, bidding against each other for public favour, by pro- mising a saving of 50 and 60 per cent! ! Of the honesty or dishonesty of such representations, it is needless to speak ; but I must state emphatically that, having closely attended to every experiment of consequence in smoke burning for a series of years, I have never yet found evidence of a saving of even 5 per cent, by any plan of preventing or consuming smoke, however 34 NO SAVING IN FUEL "perfect" And, further, I have found the more perfect the consumption was of smoke, the less was the saving of fuel ; or, more properly speaking, a greater consumption of fuel is required in raising a maximum quantity of steam from the same boiler in the same time, when the smoke is entirely prevented, than is the case when smoke prevention is not at- tempted at all. In short, perfect combustion is not perfect economy in practice, but far from it. That I have long been convinced of the futility of smoke-consuming furnaces as a measure of economy, although I have had, and have still, the strongest inducements of self-interest to endeavour to think otherwise, will be evident, if I transcribe a passage from a work published by me nearly twenty years ago, parts of which had been some years previously drawn up in the shape of reports at the request of various cotton, and other manufacturers, in Lancashire. This work was printed by desire of those gentlemen in 1837, and a second edition was published in Manchester in 1838;* and as it has long been out of print, and as it still expresses my views upon this subject, I * A Practical Essay on Steam Engine Boilers, as now used in the manufacturing district around Manchester. By Robert Armstrong, C. E. BY SMOKE-BURNING. 85 believe that no apology is necessary for the introduc- tion of the following quotation: " In nothing has the philosophical manufacturer or amateur mechanic been so much at variance with facts, and the experience of practical men, as on the subject of smoke-burning. It is perfectly true that the black carbonaceous matter, which usually escapes along with the incombustible gases, and which is the only visible constituent of what we term smoke, is all so much fuel; and when properly consumed under the boiler is undoubtedly a saving of coal ; but it unfor- tunately happens that the saving is so inappreciably small that none who have tried it fairly have been able to calculate exactly its amount, except when it has taken the negative form, which it has most frequently. It is not my intention to speak disrespectfully of any of those who have proposed to save fuel by burning, or 'consuming smoJce by combustion,' as they usually prefer to term it, for they have generally, if not universally, deceived themselves before they led others astray, as the hundreds of patents for that purpose, and the hundreds of thousands of pounds expended 86 LOSH'S DOUBLE-FURNACE over them, amply testify. Patent inventors, indeed, of improved furnaces for ' saving fuel by consuming smoke ' deserve no small share of public gratitude, from the many opportunities they have given us of ascertaining by experiment a great number of prac- tical data, and useful results, which are now available for other more important improvements." The pursuit of "smoke-burning," in fact, has been the philosopher's stone of the present century. Specu- lative and practical chemists of the brightest intellects have dabbled in it; such men as Eumford, "Watt, Dalton, and Henry were believers in its economy. I cannot speak as to Davy, but it is thought that the predilections of the great living German chemist, who has done so much for the brewing trade of England, lie that way ; at least his foremost disciples in this country hold to the yet popular doctrine that sixty or seventy per cent, of the fuel is to be saved by burning the invisible carbonic oxide gas, which now escapes from our iron furnaces in Staffordshire. On this subject I can speak with the more confi- dence from having had a good deal of practice in directing the application of various patent, and other apparatus and methods, devised to enable furnaces to consume their own smoke in different parts of this WITH ALTERNATE FIRING. 87 country, as well as in the planning and erection of boilers and furnaces generally in the ordinary way. Up to the passing of Michael Angelo Taylor's act, nearly thirty years ago, which made smoke-prevention in some measure compulsory, little or nothing had been done in the North of England except on the double furnace system of Mr. Losh, of Newcastle-on- Tyne, patented in 1815. It was more successful with chemical stoves, salt pans, and slip kilns in potteries, than with engine boilers. When applied to the latter, it was objected to on the ground that it required a larger boiler to do the same work, as well as two fires to do the work of one. I endeavoured to introduce it into Lancashire in 1827, but did not succeed until some years after the patent had expired, when the above objection was found to be untenable. The large boiler proved to be a great advantage, and alternate firing was very economical, independent of its convenience for consuming smoke. My mode of applying it was to place simply a wall of fire-brick longitudinally upon the fire-grate, nearly the whole length from the bridge to the dead plate ; but so that both sides could be charged through one fire-door. This method was used in Manchester in a boiler, em- ployed to drive a40-horse engine, at the Store Street 88 DIVIDED FIRE GRATES Cotton Mill, belonging to Mr. Win. Jones. And I afterwards erected similar divided furnaces at the Worsley Flour Mills, belonging to the Earl of Elles- mere, and at several other places, with some improve- ments, which consisted mainly in restricting the mid* feather wall to one-half the length of the grate, and making the fire-bars at the front of the grate thinner, and with wider spaces, than at the back. The air was generally let in through the sides of the furnace at about half the length of the grate ; but at Mr. Jones's, where there was a good chimney, it was admitted by setting the fire-door ajar 1^ to 2 inches, for 2 or 3 minutes after each firing. In cases where the chim- ney was low, or had a bad draught from other causes, the supplementary air was forced in over the fire by means of a small rotary fan; and where convenient, this air was in a highly heated state, say at 400 or 500 degrees. In this manner, this species of furnace was worked at the above Mour Mill, continuously with great satisfaction and economy, driving a com- mon low pressure engine working six pairs of 4 feet stones, and other machinery, with about 6 Ibs. of inferior coal per indicated horse power per hour. The proportion of the power required by the blowing fan was only about half a horse power. To show the WITH FAN DRAUGHT. 89 great advantage of either a good draft, or artificial blast, in all cases of smoke-consumption, it is proper to state here that Williams's patent system was previously tried at the same boiler with the same fire-grate area, without enabling the engine to work half the above load ; while the same system applied by the same parties to another, small engine on the same estate, with a very lofty chimney, was moderately successful. The smoke from the chimney of Worsley Mill, when in full work, was perfectly invisible, with the exception of a slight vapour during the time that the fire-door was allowed to remain open, but no longer. The situation of this flour-mill, a picturesque spot, about half a mile in front of Worsley Hall, was such that the mill was nearly hidden from view at that mansion, and its existence would have been unobserved except for the smoke which rose above the trees, before the improvement was applied. , When the smoke was prevented, the circumstance accident- ally coming to the knowledge of the Earl of Carlisle, when on a visit at Worsley, he took the opportunity of convincing himself of the facts as above related, and on their being reported to the Earl of Ellen- borough, then first Lord of the Admiralty, that 90 DIVIDED FIRE-GRATES AT CHATHAM nobleman at once ordered a similar apparatus to be erected at Chatham Dock-yard. The apparatus was accordingly applied by me to two 20 -horse boilers at the Lead mill there, for which purpose I planned the urnaces as nearly as possible a copy of those at Wors- ley, and the results were very nearly the same. The chimney stood right opposite the windows of one of the royal hospitals, to which the smoke had previ- ously been -a great nuisance; but, after six months' trial of the new plan, the chief physician of that establishment reported to the Admiralty the entire removal of the nuisance, and that the health of the inmates had been greatly improved in consequence. This Eeport was published in the " Health of Towns Gazette," in 1849. And, as I have just been in- formed by the Superintending Engineer of the Dock- yard, the apparatus has continued to work unin- terruptedly to the present time, (1856,) with uniform success."* * In 1839, 1 introduced the double furnace system into a steamer, " the William Fawcett," belonging to the Penin- sular Steam Company, and she continued to ply with the furnaces thus altered until new boilers were, I believe," intro- duced a considerable time afterwards. The arrangement of these furnaces differed somewhat from Losh's plan. Each. AND AT WOOLWICH ARSENAL. 91 About the same time several other double or divided fire-grate furnaces were erected, by other parties, at the cotton works of Mr. John Paley, and at other places, in Preston. These were more nearly on Mr. Lostfs original principle, having two separate fire- doors and two ash-pits. Mr. Howard, Mr. Thomas Hall, and a great num- ber of other parties, have introduced various modifi- cations of double furnaces since the date of Mr. Losh's patent, and more or less successfully. The last modification of the kind I have seen, was erected at a small boiler in the Eoyal Arsenal, Woolwich, by Messrs. Abernethy and Co., Engineers, of Aberdeen, in 1856. The peculiarity of this plan consists in a furnace had a damper behind the bridge, which could be shut when required, and the smoke produced in that fur- nace had then to descend through a suitable passage, into the ash-pit of the adjoining furnace, which, by this time, had burned bright, and ascending through the fire, mixing with atmospheric air, it was completely consumed. To maintain the necessary draught an exhausting fan was applied to the chimney. I simultaneously introduced other improvements which very much lessened the consumption of steam, so that, although the boiler was less powerful than before, it was still equal to its work as smaller demands were made upon it. J. B. 92 SMOKE-PREVENTING FUENACES jet of fresh air from a pipe on each side of the fur- nace being admitted alternately, to correspond with the alternate firings by which the smoke from the newly fired furnace is driven laterally, or horizontally, against the bright fire and flame of the other. This is the principle of admitting air patented by Mr. Spibey of Nottingham, several years ago, and exten- sively applied by him to single furnaces ; and by this mode of procedure the injury to boiler bottoms from cold air rising upwards against them, at or beyond the bridge, is likely to be avoided. I pass over a great many other plans of double fires, such as Gallo- way's, Bose's, Fairbairn's, Ormrod's, HicFs, Bristow and Atwood's, and others, as the principle of the whole is nearly the same, and it would occupy too much space to enter into the details. After Mr. Losh's double furnace principle, the next smokeless furnaces that came into public favour were those of Wakefield, Parkes, Brunton, and Stan- ley. The two latter being accompanied by, or mainly consisting of, fire-feeding machinery, which was neces- sarily expensive, came slowly into use, but they were both perfectly well established previous to the year 1827 ; and the only reason they are not now more frequently met with is, that they are not BY BRUNTON AND STANLEY. 93 well adapted to boilers with internal furnaces. The two former plans, consisting principally of alterations in the brickwork, came more rapidly into use in Lan- cashire. The smoke-consuming furnaces of Mr. John Wakefield, I believe, had the precedence of the other in point of time, as I had some pulled down which had been erected by him at the cotton-mill of Messrs. Clogg and Norris, in Long Millgate, previous to 1818, and which I re-constructed with my own improvements in 1830. About the same time, several were taken down at Thos. Hoyle and Sons' print-works, Mayfield, and other places, which had been a much longer time in use. In fact, Mr. Wake- field used to complain to me how Mr. Parkes, " hav- ing come after him, stole his ideas " of the split bridge, and air-valve at the back of the ash-pit. However this might be, it is certain that Parkes's system became by far the most popular; a great number of furnaces being erected by him all over the country, from 1820 to 1825, after which they were erected by him extensively in Prance. In the mean time, however, though the plans of Wakefield and Parkes were originally similar, they soon grew widely different. Wakefield persevered with thin and fre- , quent firing, thin and scientifically constructed fire- 94 SMOKE-BURNING FURNACES bars, well-arranged tools, perforated fire-bricks, for heating and diffusing the air, like Williams, and pigeon-hole bridges ; he also paid very great atten- tion to the fireman's art, and he only failed, as he said, from want of it at last. On the other hand, Parkes's system was carried on by him to the extent of enlarging and deepening the furnaces, so as to hold upwards of a ton of coal at a time. This quantity was usually introduced into the furnace during the first two hours in a morning, beginning rather thin near the bridge, and, as it became ignited, gradually increasing the thickness of the charge until within 2 feet of the fire door, where the coal was filled quite up to the boiler bottom. When arrived at this stage, the combustion was entirely that of the gas from, the raw coal. The surface of the fire then formed an inclined plane towards the bridge, and as the supply of air through the bars was thus cut off, the combustion was kept up entirely by the air through the air-valve at the back of the ash-pit, and the split bridge, which last was much wider than Wakefield made it, being commonly 3 or 4 inches, or more. During the first three or four hours of the day, the air-valve was gradually closed by the fire- man, by which time the diminished quantity of fuel BY WAKEFIELD AND PAJtKES. 95 in front of the bridge allowed sufficient air to pass through in that way. The air- valve was then shut up, and not opened again during the day. The proper action of the fire was, after this, entirely dependent upon the proper management of the dampers, and in the middle of the day the steam was regulated by the admission of less or more feed- water to the boilers. The above is a programme of the mode of proceed- ing with Parkes's system at the cotton works of Mr. John Pooley of Hulme, where I had most experience with it, thirty years ago ; and it is very nearly the same as the mode carried out at the works of Messrs. Hor- rockses Miller and Co., of Preston, up to within the last few years. There is no doubt that considerable economy was obtained by this plan, when very carefully managed, with very low pressure steam and very large boilers, even to the extent of getting an evaporation of 7 to 8 Ibs. of water to 1 Ib. of Lancashire coal ; but it was too unwieldy and cumbrous a system to continue in use more than a few years, excepting at the last men- tioned place, where special provisions were made to suit it. It is not my business, however, in tin's place, to ' write the past history of smoke-burning, so much as * 96 A NEW SMOKELESS FIRE-GRATE. to describe what is doing at the present time in that direction. With this view, I here insert a brief description of a new form of fire-bar and furnace- grate which I have had in operation for some time past, at different places with very satisfactory results ; and I expect to be able to present a more detailed account of the arrangements, accompanied by proper drawings of this and other plans of recent construc- tion, in Mr. Bourne's forthcoming work on the Steam Engine. UNIVERSAL "ARGAND" FIRE-GRATE. Like all other furnaces which burn, prevent, or con- sume their own smoke by an improved combustion of the gaseous portion of the fuel, the principle of this one depends on the admission of a sufficient quantity of fresh air to the smoky flame of bitumi- nous coal, as well as to the carbonic-oxide gas pro- duced by a thick fire of coke or from Welsh coal or other non-bituminous fuel; but it differs from all others in the place of such admission. I do not admit this fresh air at the bridge, although, by that mode, the disappearance of the smoke is usually the most perfect, because, when so admitted, it operates as a se- rious check to the draught, and lessens the power of NEW SMOKELESS FTJBNACE. 97 tlie furnace. Neither is the air admitted at or about the fire-door, because, when so admitted, it has a tendency to be drawn between the fire and the bottom of the boiler, thereby cooling a larger portion of the fur- nace, and diminishing the economy of the fuel. The necessary supply of fresh air to the interior of the furnace is admitted, in this furnace, at an interme- diate position between the fire-door and bridge; or, in fact, it is admitted between the front end and the middle of the fire-grate. This inlet aperture for the air I make through a hollow, or double bearing-bar between the first and second of two or more lengths of fire-bars, and being thus surrounded on all sides by the fire and flame, as in the Argand lamp, it might be called the " Argand Fire- grate," or furnace. (See Frontispiece.} The constituent bars of each series of fire-bars are of different thicknesses, the thickest being placed at the back for slow, and the thinnest in front for quick, or ordinary combustion, the thin bars having also the widest spaces between them. In supplying this furnace with bituminous coal, it must be charged thick on the back of the grate, until the coal reaches nearly, or quite, up to the top of the bridge, gradually sloping forward to the margin of 98 NEW SMOKELESS FURNACE. the air-space ; while on the thin or front bars,, only, it is fired in the ordinary way. No complicated apparatus of any kind is required to be attended to, and no additional tools are wanted beyond a " slice " with a blade a foot long, bent flat- ways at right angles, for clearing away obstructions in the air-space. For greater facility in doing this, a modification of the old-fashioned " stoking-bar " is sometimes placed across the ash-pit exactly under the double bearing-bar, but made in the form of a flat plate, and with a raised ledge to serve as a guide to the tool.* No great degree of care is requisite for preventing smoke in this furnace. It is only neces- sary to throw the coal boldly in, principally towards the further end of the grate, as a man would fill a cart or a barrow, and plenty of it, closing the fire- door in as short a time as possible, and the smoke will be found to be no darker than from a common house fire, provided the air-space be opened occasion- ally with the slice above mentioned. If the chimney * My improved picker-bar or " stoking plate" above mentioned is in the case of a bad draught made to turn on gudgeons at the sides of the ash pit by means of a bell crank and rod, so as to' check or regulate the influx of air through the double bearing bar if at any time required, IMPORTANCE OF SURPLUS DRAUGHT. 99 be sufficiently large, which is by far the most impor- tant condition, the smoke may thus be made nearly transparent, and, if desirable, can be rendered entirely so, by putting a little damp coal on the front part of the fire, and taking pains to clear out the air-space after each firing. The above is a recipe for constructing a smokeless steam engine furnace, than which it is perhaps impos- sible to imagine a cheaper or simpler arrangement. But it is necessary again to caution those who would adopt it, or any other plan of smoke-prevention by hand firing, that the total area of fire-grate should be at the same time increased by 20 or 30 per cent, beyond what is usually considered necessary with the common smoky furnace, and ordinary stoking. And besides this, there must be always a surplus of chim- ney power at command, by means of the usual coun- ter-balance weight to the damper, suspended in the stokehole within easy reach of the fireman's hand, while engaged in charging the furnace. Without those two provisions, especially the first, times will oc- cur in the case of sudden demands of an engine with a variable load, for steam, when the influx of air must be controlled ; otherwise the engine may go slow or stop, and smoke of greater or less opacity will at such 100 WANT OF DRAUGHT A CAUSE OF SMOKE. times issue. In the event of the engine going slow from the above, or any other temporary cause, just after a charge of coal has been put into the furnace ; then it is that the fireman finds a resort to the damper most valuable. When the draught is strong, a slight touch of the damper so as to increase the escaping area will commonly be sufficient to prevent the engine from stopping, or will enable it to recover its speed. In order to estimate the value of a large fire-grate area and surplus draught, it is only necessary to con- sider what would be the effect under the same circum- stances, with a confined fire-grate, and the damper already wide open: there is then of course no resource left but stirring the fire, and consequently stirring up a smoke at the same time.* * A quick draught is in one respect tantamount to a large fire-grate area, since it equally enables more coal to be burned in a given time, and thus increases the power of the boiler in generating steam. A quick draught, however, has this further advantage, that inasmuch as the temperature of the furnace is higher when the same quantity of heat is generated in a small space than what it will be when gene- rated in a large space, the heat is transmitted much more rapidly to the water of the boiler in the case of the strong draught by reason of the higher temperature in that case obtaining. As therefore there is more heat transmitted in INJURY FROM ADMISSION OF COLD AIR. 101 Having shown how easy it is, with a proper arrange- ment of the furnace bars, to avoid smoke, it will be useful to show how, with improper arrangements, it is also very easy to do a great deal of harm to the boilers, however perfectly the smoke may be consumed or prevented. That injury to boilers, and danger from explosions, is to be apprehended from any system of preventing smoke, in which a current of cold air is directed against the boiler bottom, is no longer a mere opinion, but a fact which cannot be gainsaid. This will appear sufficiently plain to any one who will attentively read the following copy of a Report of an examination I made of a case of the kind in Manchester several years ago. the region of the furnace, in the case of the strong draught, there will be less remaining to be transmitted in the region of the flues. In other words the flues will have less work to do, and they may either be made shorter, or the heat will be more thoroughly absorbed. J. B. 102 INJURY PRODUCED BY WILLIAMS 7 S PATENT. COPY OF EEPOET ON WILLIAMS'S PATENT SMOKE-BUENING FURNACE. u TO MESSRS. HAMNETT AND CO., CALENDERERS, WATLING STREET, MANCHESTER. GENTLEMEN, In accordance with your request, I have carefully examined into the circumstances attend- ing the injury sustained by your steam engine boiler, during the three days 7 trial of Mr. Williams 7 s patent smoke-consuming furnace, and have to report thereon as follows : Some of the plates in the boiler bottom behind the bridge appear to have been exposed to a considerable degree of expansion and contraction alternately, arising from frequent alternations of temperature, by which means the rivets have been dragged successively in opposite directions, until they have become loosened in the rivet holes, and the boiler has become leaky."* One plate is also what is usually called "burnt out/ 7 which is what generally happens when one side of an iron plate is frequently and suddenly heated and cooled, while * See illustrations of similar effects in figures 5 and 7, chap. iii. of this work. REPORT TO HAMNETT AND CO. 103 the other side, from its contact with the water in the boiler, is kept at a moderately uniform temperature. In this case, also, owing to the necessarily laminated structure of wrought iron, combined with the heating and cooling process above described, " a blister " has arisen in one of the plates, and this blister has been the immediate cause of the giving way of the boiler, by so far weakening it as to allow the pressure of the steam and water to force down the plate in that parti- cular place. The main cause of the above results is clearly to be traced to the imperfect construction of the furnace, inasmuch as the passage for the admission of fresh air to the flame behind the bridge, is unprovided with a valve or other means of regulating the quantity of air so admitted, or the time of its admission, within the reach of the engineer whilst engaged in firing the boiler. To enable me to explain this point more fully to your satisfaction, I may state that this mode of pre- venting, or (as it is most commonly called) "burning" the smoke, by admitting atmospheric air at or behind the bridge of the furnace, has been long known, and frequently practised in Manchester since it was first generally introduced here by Mr. John Wakefield 104 REPORT TO HAMNETT AND CO. more than twenty years ago. This gentleman also practised the method of diffusing the air through several small apertures inside the furnace chamber, in the same manner as Mr. Williams. But in all Mr. Wakefield's furnaces, as well as those of Mr. Parkes, that I ever saw, the passage through which the air was allowed to communicate with those apertures was supplied with a regulating valve for the purpose of admitting the proper quantity of air, suitable to the varying state of the fire, or to shut it off at the dis- cretion of the engineer or fireman. And the uniform practice of all operative engineers has always been, when no flame was passing from the fire, and conse- quently no smoke being made, to shut the air off entirely. In your case, however, the furnace is so arranged that a constant stream of cold air is uniformly rush- ing into the main furnace chamber or flame-bed of the boiler at all times, and whether there is a flame passing over the bridge or not.* * I am aware that the production of the invisible carbonic oxide gas, from a thick coked fire, may sometimes create a demand for air when no black smoke is passing. But I con- tend that such air should be supplied through the grate, and not behind the bridge, unless carefully regulated. REPORT TO HAMNETT AND CO. 105 The certain and inevitable consequences of this state of things are, that every time the fresh coal is thrown on the fire, and a flame is produced sufficient to reach through the throat of the furnace, the current of fresh air passing directly into [or against] the flame from below, drives the latter right up against the boiler bottom in the manner of a blow-pipe, causing it to impinge with peculiar intensity against that portion of the boiler bot- tom immediately exposed in the direction of the blast. On the other hand, as soon as the fire on the grate has burned bright, and the flame does not extend over Hyper criticism might contend that, instead of a " stream of cold air," it would have been more correct to say streams of cold air, inasmuch as the air was supplied through a perforated plate between two bridges, which did not form, strictly speaking, the split or double bridge of Parkes, being much wider apart. These numerous streams, however, united and became one stream after passing through the meshes of the "Patent Riddle," which riddle grating or perforated plate formed the special claim of the patent, and could be of no earthly use, unless indeed it had been used for heating the air. That purpose; however, was especially disclaimed in the patent, and the air, in this particular case, was brought in a separate channel at a distance from the boiler intentionally that it might be cold, and that all access .to it by the engineer might be cut off. 106 REPORT TO HAMNETT AND CO. the bridge, the COLD air striking against the same part of the boiler bottom, which had just before been so unduly expanded by intense heat, a sudden contrac- tion of the metal necessarily ensues, besides a great waste of fuel, and difficulty in keeping up the steam. I have long paid great attention to the operation of smoke-burning furnaces generally, and more particu- larly to those constructed on the principle so imper- fectly attempted by Mr. Williams, that is, by supply- ing to the carbonaceous products evolved, their full saturating equivalents of oxygen for effecting the most perfectly attainable combustion of their elements, and thereby preventing smoke, but which can only be safely effected by carefully regulating the admission of air to the flame, for which, in Mr. Williams' s plan, there is no provision made whatever. I have no hesi- tation in stating that the result of my experience is, a confirmed opinion against the economy of the process ; being convinced, that, in ordinary circumstances, there is more fuel wasted by the admission of cold air to the boiler bottom, than is saved by the most per- fect consumption of the smoke. This conviction has been forced upon me by a careful and unprejudiced examination of a great many steam engine furnaces erected both by myself and others, including several constructed by Mr. Williams himself. REPORT TO HAMNETT AND CO. 107 I may take the liberty of concluding this report with a caution which I have been in the habit of giving verbally to all those who have occasionally consulted me on this subject for some years past. It is that I have reason to believe that many extensively fatal explosions of steam boilers, not otherwise satis- factorily accounted for, have arisen from similar causes to those detailed above, namely frequent and sudden alternations of temperature at the lower part of the boiler, inducing a tendency to burst downwards, of which instances are constantly occurring. In fact, in the case of your own boiler, the minor explosion it has experienced, may be considered in the light of a very narrow escape, for if the blistered plate had been of rather a better quality of iron, so as to have held out a few days longer, or until one or two of the adjoining already injured plates had become nearly as weak as itself, in all probability they would have given way simultaneously, and produced an extensive explo- sion, the effect of winch is usually, by reaction, to force the boiler upwards, sometimes to a considerable height through the supervening buildings, in a way that has too frequently created an enormous destruc- tion of life and property. EGBERT ARMSTRONG. 108 CONTROVERSIES OF RIVAL PATENTEES. The reason for giving, perhaps, undue prominence to the above letter or report, is that it was not origi- nally published by me, that is, if printing and giving away a large number of copies may be considered as such but by Mr. Joseph Williams, of Liverpool, then (in 1841), as now, well known as the proprie- tor of the patent smoke-burning furnace of his brother- in-law Mr. Kurtz, a scientific chemist of considerable eminence. The letter itself was properly a private business one, which, with other evidence, was, after revisal by me, put into the hands of the solicitor of the firm of Hamnett & Co. for legal purposes. Although not then called on to justify the publication, I did not object to it, because Mr. Joseph Williams represented to me the injury his character and that of his patent, which was for the use of hot air, might sustain in being confounded with those of Mr. Charles Wye Williams, whose patent was for the use of cold air, owing to both persons having the same surname.* Consequently many thousand copies of the report were printed and circulated by Mr. Joseph, setting * It is remarkable that four different persons of the name of Williams, Irish, English, Scotch, and, I believe, Welsh were the holders of smoke patents during the same year. The first and second of whom only we now refer to. CONTROVERSIES OF RIVAL PATENTEES. 109 forth the distinctive appellations of himself and Mr. Charles Wye at full length. This procedure was also followed by Mr. John Chanter of London, the proprie- tor of numerous smoke patents, publishing the same thing. The object of both those gentlemen was pro- bably the same, that of demolishing the business of a rival patentee, which, there is no doubt, they did most effectually; raising, at the same time, some rather undignified discussions in the public press on their various claims to notoriety in saving 30, 40, and 50 per cent, in fuel. In those discussions, except in self- defence, I took no part, having no pecuniary interest in any smoke patent, nor any sympathy whatever with any of the combatants. So effectually had all public interest died out in the above discussion, which was supposed, as usual, by many to be settled in favour of those who care to have the last word, that I did not think it necessary to allude to the subject in my " Rudimentary Treatise on Steam Boilers," in 1851. The subject how- ever, has been revived by the Society of Arts awarding one of its prize-medals for an essay on smoke-pre- vention, among others, to Mr. C. Wye "Williams, who must have convinced the society that, "though beaten, he can argue still." In this prize-essay Mr. 110 ITERATION OF ME. C. W. WILLIAMS. Williams has endeavoured to revenge his former discomfiture by an onslaught on the whole of the present generation of patent smoke-burners, which I do not notice, but for the unfair use he makes of the above report misquoting, garbling, and perverting it in every possible way.* Hence the obligation I am under in giving my report at full length as above. Considering that, although I stand sufficiently ab- solved from the necessity of noticing Mr. Williams any farther, there are one or two others whose prac- tical abilities as engineers the public hold in high respect, who have been led astray in this matter of smoke-prevention, but who can have no interest or desire, except to be set right as to facts. I think it proper here to narrate the results of some experi- ments I cotf2ucea upon smoke-burning in 1843, with the view of illustrating some of the points then under controversy. This information is afforded in the following memorandum : * See Ms letter on the smoke nuisance in the Engineer newspaper, for May 30th, 1856. EXPERIMENTS ON SMOKE -BURNING. Ill ACCOUNT OF EXPERIMENTS CONDUCTED AT THE COTTON FACTORY OF THOMAS HOULDSWORTH, ESQ., M.P., IN MANCHESTER, IN 1843, IN ORDER TO DECIDE ON THE ECONOMY OF SMOKE-PREVENTION. It will be remembered that a select committee of the House of Commons was appointed to investigate the smoke nuisance question in 1843, the results of which investigation were published in a blue book about the end of that year ; and on the evidence con- tained in that and other reports, Parliament afterwards proceeded to pass several new laws on the subject a very proper thing in itself, if founded upon truth in- stead of the most erroneous statements to the eifect that manufacturers would be greatly benefited by the measure in the saving of fuel thereby ensured. Among other questionable evidence, by much less reputable parties, published in this blue book, was a statement by Mr. H. Houldsworth, supported by a long array of tables and diagrams, asserting that, " by an admission of air to the extent required to pre- vent smoke," into the " body " of a steam-boiler fur- nace, "much additional heat is produced, more steam raised from the same weight of coals, and more water evaporated in the same time." Particulars of 112 EXPERIMENTS ON SMOKE-BURNING. four experiments are detailed in order to show that a gain of 35 and 36 per cent, was "made by admit- ting air partly at the door, and partly at the bridge, through one of Mr. C. W. Williams' s diffusion- boxes/' (or patent perforated plates.) In the ap- pendix to the report it is stated that, " in each experi- ment 1840 Ibs. of Knowles's Clifton coals were burnt; a free-burning kind, much used in Manchester. The boiler was one of Boulton and Watt's, 24-horse power, waggon shape." The following extract is from Table B., Appendix No. 5, page 201, referred to in the evidence of Henry Houldsworth, Esq. Vide Q. 1100, page 102, July 27th, 1843. Effect per Water evapo- Minute. rated by Econo- AIR. Coals burnt. Water Eva- porated. 1840 Ib. of Coal lib. Coal. mic Effect. Ibs. galls. galls. Ibs. No air 4-64 2-5 992 5-41 106 43 square inch constant aperture 4-68 3-21 1,263 6-85 135 Air, regulated partly by the eye and partly by a scale, varying in some degree with the action of combustion. 4-43 3-09 1,280 6-94 134 No air 4-43 2-3 942 5-12 100 MISREPRESENTATIONS AS TO ECONOMY. 113 The first effect of Mr. Houldsworth's published statement was the industrious propagation by some of the Manchester and Liverpool Journals, of the fallacious inference that 35 or 36 per cent, in fuel was to be saved by smoke-burning instead of 25 per cent, only, supposing his experimental data to be right. That however was denied by many manufac- turers, and the result was a request to Mr. Houlds- worth to repeat any of his experiments likely to show them so very desirable a result. This after some preparation was agreed to, and I was appointed by the firm of Geo. Clarke and Co. as their consulting engineer to witness the experiment, and was also retained for the same purpose by other manufacturers who felt great interest in the subject. These trial experiments took place by appointment on the 19th and 20th December, 1843, and the following summary of the results, after under- going the revision of Mr. Billington, who super- intended the experiments on the part of Mr. Houldsworth, and a written acknowledgment of the latter gentleman to their correctness, was transmitted by me to Messrs. Clarke and Co., and the other firms interested in the matter, also to Mr. Wm. Pairbairn and other Engineers, who appeared to be so. 114 FAILURE OF WILLIAMs's FURNACE. SUMMARY. Results of the experimental trial of the comparative economy of Mr. C. W. Williams 9 s patent system of smoke prevention and the ordinary plan. " The exact results of the smoke-burning experi- ments made at Mr. Thomas Houldsworth's works, on the 19th and 20th of Dec. 1843, are as follows: " At one boiler having Williams' s Patent Argand Furnace attached that is with a permanent aperture admitting a continuous current of air through a perforated plate or " diffusion box" behind the bridge, by the consumption of 1150 Ib. of coals, the evaporation was 569^ gallons of water in 5 hours 22 minutes; and on the following day, namely, the 20th of December, 1843, with the same boiler, the same quantity of coals from the same heap, and every thing exactly in the same state as before, except that the aperture for admitting air at the bridge was kept carefully closed the whole time, and the holes in the fire door plugged up, the evaporation was 713J gallons in 5 hours and 20 minutes. The experiments commencing each day at the same hour." Eate of evaporation per Ib. of coal is accordingly : With air admitted 4*95 Ib. water to 1 Ib. Coal. "Without ditto.. 6-2 Ib. lib. MISREPRESENTATIONS AS TO ITS PERFORMANCE. 115 Difference 1*25 Ib. or 25 per cent, more steam in favour of the ordinary plan and against smoke-pre- vention, instead of 35 per cent, by parliamentary evidence the contrary way ! After so signal a failure as the above, what must we think of a statement which the publisher has been influenced by Mr. Williams to msezi twice over in an un- authorized " Appendix" to a surreptitious edition, mis- called by him the third of my " Eudimentary Treatise" to the effect that Mr. Houldsworth had " as a result of his reading Mr. C. W. Williams' s book on com- bustion" reduced his consumption of coal from 20 to 17 cwt. per hour? My answer to this is, that previous to his adopting Williams' s system, he was using at the rate of 7| Ib. of coal per indicated horse- power per hour full 20 per cent, more than the average rate of other manufacturers at that time, which left room for saving even by the adoption of a bad plan. Mr. Houldsworth^ s consumption was not therefore the " ordinary," but an extraordinary and extravagant consumption of coal. This is amply authenticated by various duty report papers of Manchester engines now before me ; a fact which constitutes him a very weak authority on the subject, the only nominal (engi- 116 PRACTICAL REMARKS ON SMOKE-BURNING. neering) support he occasionally had in Manchester to the contrary, notwithstanding. Many other proofs abound, utterly condemnatory of the perfect combustion notion, in its application to steam engines ; but as that system is now perfectly defunct, if it ever was alive, except on paper, I shall here conclude with some observations printed several years ago on "perfect" and "imperfect" combustion, for the use of those who require a more rational theory on the subject, and which I now take the liberty of entitling A THEORY OF THE BEST POSSIBLE COMBUSTION IN STEAM ENGINE FURNACES. It is true that smoke is a result of imperfect com- bustion, but it is also true that combustion may be still more imperfect without smoke, and be attended with a much greater waste of fuel. In a steam engine furnace, there never was, and never can be " Perfect Combustion," even in theory much less in practice. In the nearest apparent approach thereto, when no visible smoke escapes from the chimney, there always arises from a fire of tolerable thickness a certain quantity of unconsumed inflammable gas, chiefly car- bonic oxide, whilst at the same time, a very large AIR NECESSARY FOR COMBUSTION. 117 proportion (according to experiments by Peter Ewart and John Dalton about one half) of the gaseous products passing off by the chimney consist of at- mospheric air unchanged, that is, containing its full proportion, about one-fifth of oxygen. Now, since it is impossible to increase the supply of oxygen, which by combining with the fuel in the furnace is alone the cause of all the heat produced, without at the same time increasing the supply of the other com- ponent of the atmosphere, consisting <A four-fifths of it, namely, the nitrogen ; and allowing, as above, one half only of the oxygen to be available, it follows that about nine-tenths of the atmospheric air admitted into the furnace, and heated to a temperature of about seven hundred degrees, is carried off by the chimney for no purpose whatever, except to enable the remaining one-tenth to support the combustion of the fuel. An exception may be taken to this on the ground that some part of this waste heat may be recovered by an extended heating surface of the boiler; that, however, is limited in practice by other circum- stances, and does not affect the above conclusion as regards the furnace considered by itself. Whether heat is a material substance or not, which 118 SUPPLIES OF AIR AND FUEL is immaterial to this question, it is quite certain that in its production from the burning of common bitu- minous coal, the main elements concerned are carbon, hydrogen, and oxygen, and that the complete conver- sion of these three substances into carbonic acid and ater without waste, is the only common-sense idea that can be conceived of complete or f ' perfect com- bustion." And, if we could have a continued supply of oxygen without its accompanying nitrogen, such complete combustion might be possible, but as we can only have these two elements mixed as we find them in the atmosphere, and one of them having to be separated from the other, as they pass through the furnace, whilst so large a portion as nine-tenths of the whole is of no use in the process, the case is considerably altered. Take, for instance, any given ordinary furnace, and supposing it to be in operation and supplied with fuel at a given uniform rate, if we then suppose the air supporting the combustion to be supplied at a uni- formly increasing rate, it is certain that a maximum point, in the relative proportions of the air and fuel, must be somewhere arrived at, where the expenditure of heat on the liberated nitrogen and other incom- bustible products escaping by the chimney mustcoun- PROPORTIONATE AND CONTINUOUS. 119 terbalance the heat created by the consumption of that portion of any combustible gas or smoke that would otherwise pass off unconsumed in the same way the former increasing as the latter diminishes, and vice versa. This maximum point of BEST POSSIBLE COMBUSTION once attained, we can neither pass nor fall short of it without diminishing the temperature and eventually stopping the process ; or, in other words, the oxygen which alone supports the combustion, must not only create as much heat as is sufficient for heating itself, but also as much as is required to heat up to the same degree all the air or gases with which it is in contact, otherwise the combustion will not go on at the same rate, and consequently a lessened supply of Steam to the engine results, and less power, the only true measure of heat, is produced. The natural conclusion from the above theory which is also in strict accordance with all success- ful experience is, that the most economical method of firing a steam engine boiler, from which a con- stant quantity of steam is required, must be by a regularly uniform supply of fuel to the furnace, and a similarly regular supply of air through the .fire-grate "and no where else," with a uniform 120 PRACTICAL SMOKE-BURNING. though moderate emission of smoke, visible or in- visible, from the chimney; visible within certain limits of density of shade as the combustion is more or less imperfect, being least imperfect when the combustion is quicker and the resulting products contain the largest proportion of carbonic acid gas and steam, holding in suspension a thin grey colour- ing of carbon or soot, which constitutes ordinary smoke ; invisible when the combustion is slower and more imperfect, allowing the carbonic acid first formed to be replaced in the escaping products by a large quantity of carbon, in the form of carbonic oxide gas, thereby wasting, at least theoretically, nearly half the available carbon of the coal. CHAPTER III. EXPLOSIONS: AN INVESTIGATION INTO SOME OF THE CAUSES PRODUCING THEM, AND INTO THE DETERIO- RATION OF BOILERS GENERALLY. How to obtain sufficient strength to resist the dis- ruption of the materials of which boilers are composed is one of the principal considerations usually advanced in investigations respecting boiler explosions. Setting this topic aside, for the present, and dismissing the discussion of theories of explosions, we shall endea- vour to collect here the practical results of the most uniform experience relative to the explosions of boilers which are imputable to common causes. We shall also examine such experiments as illus- trate the proper forms and dimensions of boilers in common use, and shall recapitulate the principal sources of weakness arising from ordinary tear and wear, from improper management and from other usual incidents in practice. 122 EXPERIMENTS BY COMMITTEE AMERICAN EXPERIMENTS ON EXPLOSIONS. The most authentic illustrations of the inferior limit of the thickness of metal proper for boilers, are two experimental explosions purposely produced in the course of a series of very important investigations, undertaken by a committee of the Franklin Institute of the State of Pennsylvania, at the request of the American House of Representatives, for whom the report of these experiments was first published in America in 1836. The immediate object of the two experiments in question was "to observe accurately the sort of bursting produced by a gradual increase of pressure within cylinders of iron and copper." This course was pursued because it had been assumed by many, and indeed the opinion was very generally entertained in this country as well as in America, that ruptures produced in copper boilers would not bear the cha- racter of explosions, but that a mere rending would take place, giving an easy escape to the contents. In pursuance of this investigation, two cylinders were prepared of such a size as it was thought would make a small thickness of material illustrate the question, OF FBANKLIN INSTITUTE. 123 " by rending at a pressure which was easily attain- able/' In this respect the committee would have found less difficulty if they had made the boilers of a larger diameter; for it appears they really had considerable trouble in causing the boilers to explode at all. o^owever, they did at last succeed, and the results afforded a direct answer to the question between iron and copper, proving the entire want of foundation for the opinion which asserted the superior safety of the latter. Collaterally, also, those results afford good grounds for the first step of a general inquiry into the causes of the explosions of boilers. EXPERIMENTAL EXPLOSION. The iron boiler used in this experimental explo- sion was cylindrical, 10 inches long by 8| inches diameter, and l-50th of an inch thick, with ends l-20th of an inch thick, to which the curved portion was fixed by rivets, nearly touching each other. A single opening in one of the ends of the boiler admitted the water, which was then furnished with a screw, also with a tube and piston, connected with a small spring weighing machine. AMERICAN EXPERIMENTS ON EXPLOSIONS " Upon the cylinder of this machine a ring was placed, which was moveable along the cylinder by a slight pressure ; this ring was forced towards the end of the cylinder nearest to the boiler head, as the spring was bent, and remaining in its place as the spring relaxed, served to register the maximum pressure to which the piston had been exposed previous to observ- ing it/'* FIG. 3. The small iron boiler thus prepared was half filled with water, and placed on a charcoal fire, and the steam got up ; but owing to a leak in the riveting, the steam escaped so fast that the operators were unable to burst the boiler on the first trial. The boiler was, however, replenished with water, and set lower in the fire, which was again urged, when at last, with some difficulty, an explosion was produced. * See the original Report, page 66. p I 1 BY COMMITTEE OF FRANKLIN INSTITUTE. 125 So little dependence can, in general, be placed on the relations made by witnesses of accidental ex- plosions, and so rarely have explosions been inten- tionally made for the purpose of illustrating this ques- tion, that, for the sake of accuracy in preserving all reliable facts, the different members of the committee simultaneously addressed their attention to the different circumstances which had to be observed at the time the explosion took place. " Part of the committee were engaged in observing the progress of the experiment at this moment. The fire was near the middle line of the boiler,* burning not strongly near that line, but very rapidly below the boiler ; the steam issued freely through the leak before alluded to, and the whistling sound which it produced, and which had increased gradually in strength, as the experiment progressed seemed con- stant. The length of time during which the steam had escaped showed the water to be low, and induced the supposition that a second time the object would fail; when an explosion occurred." * As the boiler rested horizontally in the fire, and was half filled with water, this middle line and the water surface would nearly coincide. 126 INCIDENTS OF EXPLOSIONS THE CROSS-LANE MANCHESTER EXPLOSION. After recounting the incidents of this case of arti- ficial explosion, I shall now proceed to describe some of the cases of real explosion which have occurred in practice. One of these cases is that of an explosion which took place several years ago, by the bursting of a small cylindrical boiler, of about three feet in dia- meter, used for the purpose of working a six-horse non-condensing engine, at a pressure of 60 Ibs. per square inch. It had two safety valves, each of about a square inch area, and both were stated to be in full action at the time the explosion took place, having commenced blowing off steam a few minutes before. The result of this explosion was, that the wrought- iron end of the boiler next to the furnace was torn away, principally by splitting the angle iron, which was barely f of an inch thick, and thrown more than 20 yards off, carrying the fireman six or seven yards of that distance, who, together with another man, was killed on the spot. The body of the boiler was driven in a contrary direction, through both the external walls of the engine-house, one nine and the other four- teen inches thick, at the same time carrying away the OF BOILERS IN MANCHESTER. 127 steam-engine itself several yards into a field, at the other side of the building.* THE JERSEY STREET, MANCHESTER, EXPLOSION. Another apparently similar kind of explosion to that just described, took place in October, 1841, at the Machine Manufactory of Messrs. Elce and Cot- tarn, in Jersey Street, Manchester. This boiler, like the previous one, was employed to drive a six-horse high pressure, or non-condensing engine, having an eight-inch cylinder and a two-feet stroke, working usually at a pressure of from 26 to 36 Ibs. per square inch. The safety-valve, which was of the common kind, with a packed spindle and stuffing-box, was ad- justed by means of a Salterns spring gauge, to blow off at 40 Ibs., beyond which pressure it could not be screwed down. This boiler was a cylinder of 9 feet 6 inches in * This explosion took place in October, 1832, at a saw- mill in Cross-lane, Manchester, belonging to Mr. Greorge Jones. The engine and boiler were both quite new, having only worked a few days, although at the time of the explo- sion the engine had been stopped for a few minutes for the purpose of adjusting a strap on the machinery. 128 STICKING OF SAFETY VALVE. length,, with flat ends, 3 feet 10^ inches diameter. It was made of good iron, f inch thick all through, and had been some few years at work. The two ends, or as the Americans call them, " heads " of the boiler, were braced to each other by one longitudinal wrought iron stay bar through the centre, attached at each end by a wrought-iron strap and cotter. It was the giving way of this strap, against which the cot- ter was driven, through a slot in the stay bar, in the usual manner adopted for low-pressure waggon boilers, which was the immediate cause of the explosion. The strength of the iron, however, at the place of fracture, when examined by good judges, was pro- nounced to have been capable of resisting a pressure on the end of the boiler of at least 100 Ibs. to the square inch. STICKING OF SAFETY VALVES. That the support above mentioned should have given way when the safety-valve was free to open at 40 Ibs. per square inch, or less than one-half the pressure that it was proved to be thoroughly able to sustain, is one of the anomalies we are so frequently meeting with in these investigations. I would here call attention to this point ; because nothing would be STICKING OF SAFETY VALVES. 129 easier than to make short work of such cases, by saying that the safety-valve must either have " stuck or jammed" or otherwise must have had additional weight put upon it at the time. This, in fact, was the conclusion come to by three practical engineers of the highest eminence, who agreed to deliver to the coroner's jury a joint report on this case. This sticking and jamming of safety valves, is, in any case whatever, so extremely improbable, that a resort to this explanation, without actual proof of its existence, is much to be reprehended. In this pa,rti- cular case, it is true the safety-valve was found broken off and blown to a considerable distance, having its spindle somewhat bent, and it had been wrapped with a certainly improper packing of hemp ; but even if the bending of the spindle had been done previously to the explosion, (which was in the highest degree improbable) the "sticking" thereby created in the packing, could not have added many pounds per square inch, to the resistance offered to the free escape of the steam."* * NOTE BY A3" EMINENT GOVERNMENT ENGINEE R. " I fear that it is difficult to say what amount of force is sufficient to raise a safety-valve whose spindle is bent, and therefore I would suggest that * a measure ' be not as- K 130 A CONVENIENT PRETEXT. Not a much better stalking horse than this uni- versal sticking point is the criminal overloading, or " making fast" the safety-valve. Any imputations of this kind without the most clear and positive evi- dence, both direct and circumstantial, is simply beg- ging the whole question. There is very rarely, except in the case of locomotives, any inducement to do any thing of the kind, but very frequently the contrary, as was very likely to be in the case before us. For the engine had not started, and from the proved careful habits of the engineman who was killed by the explosion, it is much more probable that he opened or eased the safety-valve, by removing all or part of the load upon it, and my firm conviction was, at the time, that he did do so, and that the boiler blew up on the instant, or in a few seconds afterwards. , signed. "I know a very serious case of rupture of a new boiler, attended with loss of life, which was solely attri- butable to a bent spindle, in my opinion, * * * but I must confess that this conclusion, mine as well as yours, being matter of opinion, simply, might be taken indiffe- rently, according to the notion of the reader. " I agree with you that ' sticking ' of safety-valves, pro- perly so called, is extremely improbable. " EXPLOSIONS FROM WANT OF WATER. 131 DEFICIENCY OF WATER. In the Jersey-street boiler, as well as in that at Cross-lane, might be seen distinct traces of the water having been too low. There were certain marks left by the sedimentary deposits all around the interior of the boiler, showing the high and low- water marks. These indelible water lines gave evidence unmistakeable, that the water had been too low. Since my attention was first directed, many years ago, to these peculiar high and low water deposit marks, I have personally in- spected the internal condition of many hundreds of steam engine boilers, and I have missed no oppor- tunity of testing the accuracy of these indications of water level, by a reference to other well- ascertained facts, and have found that mutual accord which was to have been expected. In the Jersey-street boiler, some of the most dis- tinct, and probably the most recent of those water- marks were within twelve inches of the boiler bottom, at which point, and at least an equal distance below the proper level, it is extremely probable the surface of the water was, when the explosion took place. 132 REFERENCE TO AMERICAN EXPERIMENTS. Now, it is to a deficiency of water to this extent, com- bined with a sudden opening of the safety-valve, causing a rapid ebullition, and a spreading of the water over the super- heated side of the boiler, that I principally attribute the frequency of explosions. COMPARISON OF THE AMERICAN EXPERIMENTAL EXPLO- SIONS WITH ACCIDENTAL EXPLOSIONS. We may now return to the American experi- ments, with the advantage of the illustrations afforded by the two Manchester explosions, in which, in the words of the committee, the " sort of bursting " pro- duced in each case, was precisely of the same kind. In the American Report, speaking of the iron boiler, it is stated that " the explosion tore off one of the heads b c (Kg. 3,) of the cylinder, projecting the other parts of the boiler in an opposite direction, carrying with them, a portion of the dis- tance, the iron cylinder forming the furnace, and scattering the fuel in every direction. " The report attending the explosion, resembled that from a small mortar fully charged, the steam mixed with the smoke was not considerable in quantity, and few marks of water were to be seen. The boiler head EXPLOSIONS FROM WANT OF WATER. 133 was thrown 15 feet, the boiler and spring register about 6 feet, and the furnace, weighing about 45 pounds, was overturned and carried 4 feet. The pressure indicated by the register, was 11J atmo- spheres, (about 154 Ibs. per square inch.) "In examining the boiler, it appeared that the head b which was thrown off, had first struck against the iron furnace, which had deflected it outwards ; this is shown by the indentation c in the' figure. This head was forced off all around, in the line of rivets which attached the head to the boiler, the metal remaining between the rivets being less than the space occupied by them." The accompanying figure (4j) will give an accurate idea of the appearance of the boiler after its rupture. LOSS OF WATER BY BLOWING OFF AND LEAKAGE. The Committee then goes on to give the details of an experiment with a copper boiler of the same dia- meter, and of similar construction, which was ex- ploded by a pressure supposed to be of about, sixteen atmospheres, after having failed in the first attempt owing to leakage, as in the former case. The sound .or report was stated to be like that from an 8-inch 134 REFERENCE TO AMERICAN EXPERIMENTS. mortar. The copper was torn from the heads, un- rolled, and irregularly bent; adhering to the heads for only a short distance, as shown in the cut (Fig. 4), and the heads were bent outwards. The thickness of the copper at the line of rupture, varied from '025 to 035, say about 1-32 of an inch. FIG. 4. The description of the above carefully recorded experimental explosions, shows that the steam was allowed to rise gradually, in both cases, until the boilers gave way. This gradual and slow increase in the pressure of the steam, was in great part caused by the leaks impossible to be avoided in the riveting of EXPLOSIONS FEOM WANT OF WATER. 135 sucJi very thin boilers ; a circumstance which enables us to compare these experiments with other experi- ments at boilers under different circumstances, but in very similar conditions as to leakage of water and steam, which we so frequently meet with in ordinary practice. A not very dissimilar condition is that of the continued escape of steam, from the safety-valve or otherwise, and the consequent loss of water during the time an engine is standing, and the force-pump not at work, such as has been already de- scribed in speaking of the Cross-lane explosion. Another instance, is the case of a Locomotive when running on a railway with the steam either blowing off, or being continually consumed by the engine at a pressure or strain upon the iron very much greater than either of the Manchester explosions we have described, but with this important difference, that while the loco- motive is running, the full supply of water is easily kept up. In nearly all explosions of locomotives that have hitherto occurred, which have been very few, and of these only a very small number have taken place while the engine was running, there has been always good reason for assuming a deficiency of water in the boiler. There is another condition that admits of a com- 136 EEFEEENCE TO AMERICAN EXPERIMENTS. parison with, the American explosion, and which is, perhaps, the most important of any yet enumerated. It is the condition of an ordinary stationary boiler when the water surface is allowed to become too low from unseen leakages at the lower part of the boiler at certain times when the engine is standing, and consequently the feed pump not at work. It will be well to bear all particulars of frequent undue leakage in mind for future application, as they have an im- portant bearing on the general subject of boilers in other respects besides those above named, and they have been entirely overlooked by the American com- mittee. It appears that both the American boilers ex- hibited proofs of the water having been too low at the moment of explosion. Speaking of the copper boiler, the report says : " The marks of the sediment remained in the boiler, and indicated that the water was about an inch deep when the boiler exploded." Much more steam being formed, and more water left, at the moment of explo- sion, in the copper than in the iron boiler. It was also observed that the steam increased " more rapidly as the quantity of water diminished," and the com- mittee add the following remark as a conjecture : SUGGESTIONS OF AMERICAN EXPERIMENTS. 137 " It is possible there may be a relation between the space occupied by the water and that in which the steam is formed) most favourable to the production of steam, and when this was attained, a rapid rise of elasticity took place. 33 It is much to be regretted that no farther experi- ments were instituted in the direction of this sagacious suggestion. The committee, however, were under the necessity, from the nature of their instructions, of investigating some particular averments of Mr. Perkins, together with some episodical refinements that seemed to have little connection with the great facts they were in quest of. In reading the above passage in italics, in the report, and knowing that this branch of the inquiry ended there, it is difficult to help lamenting that it is as if Columbus had turned back when he was within sight of land. Nothing remarkable occurred previous to the instant of the explosion of the copper boiler, and the members of the committee employed in the experi- ments were engaged in observing the boiler at the instant it exploded. When " a dense cloud of smoke and flame, capped by steam, rose from the pit,* the * See note A at the end of this chapter, concerning the explosion of a large boiler at Bolton, Lancashire. 138 SUDDEN PRESSURE WITHIN THE BOILER. stones and combustibles were widely scattered, and the boiler was thrown in a single mass about 15 feet from the furnace." This copper boiler was rent in the manner shown in the figure (fig. 4), giving way in an irregular line, just above the probable water line on one side of the boiler, but not conforming to it. The lowest points of the two heads of the boiler before the explosion were at d and b (see fig. 4, page 134). CONTRARY CONCLUSIONS DRAWN FROM THE AMERICAN EXPERIMENTS. The American committee conclude their remarks on these experiments generally, by observing that "all the circumstances attending the most violent explosions may occur without a sudden increase of pressure within the boiler." This, no doubt, is true as & possibility, but it does not appear to me to express correctly the circumstances usually attending explosions in practice. The committee indeed do not say that it does do so, but such a conclusion is a natural inference from their averments. My experi- ence, however, and a generalisation of all the facts which have come under my observation during a COMPARISON OP CONCLUSIONS. 139 large practice in boiler engineering, conduct me to a different conclusion. My opinion is, that, in the most violent explosions that have occurred, there is always a concurrence of circumstances attending them, which show that a sudden increase of pressure within the boiler has taken place, either at, or immediately before, the moment of explosion; and further, that, without such concurrent circumstances, or some of them, the explosion would not have taken place at all. COMPARISON OP CONCLUSIONS. If we briefly express the conclusion of the com- mittee in similar terms to those used in the enuncia- tion of our own theory it amounts to this, namely, that all the circumstances calculated to produce an explo- sion may " occur" without an explosion taking place. While, in opposition to this, I maintain that those same circumstances cannot "occur" simultaneously without an explosion being produced. Considering both these conclusions as separate propositions, and one or the other to be proved by its general agreement with facts as they arise in other cases that come before us, we may begin by taking, as an instance, the first experiment with the iron UHI7BR3ITT 140 SUGGESTIONS OF AMERICAN EXPERIMENTS. boiler as given by the committee. Here tliere can be no doubt that all the circumstances which they con- sidered to be necessary to cause an explosion existed, and yet no explosion took place. We, however, hold that no sudden increase of pressure took place, and therefore it was that, in the first instance, no explosion ensued. Thus we see that one of the most important circumstances is wanting. Let us however see what all the facts were, by which circumstances were so constituted as to fail in producing the explosion. In the first place, the boiler was without a safety- valve, unless the leak in the riveting may be con- sidered as having the effect of an imperfect one. Secondly, the water surface was proved to be con- siderably below its proper level, and therefore the upper portion of the sides was exposed to the risk of becoming overheated. Now, here are facts constituting two predisposing causes, the shutting up the steam and the deficient depth of water. But the first was confessedly im- perfect, the leak allowing the steam to blow off, from the commencement of the experiment, so fast that it could not be raised to the bursting pressure, even gradually, not a bad illustration, as the result proved, of the safety of a badly fitted safety-valve, SUGGESTIONS OF AMERICAN EXPERIMENTS. 141 or one in bad order, not tight. And the other fact, we may also show, was only imperfectly calculated to produce a sudden increase of steam-pressure ', in the only way that such a thing can be conceived to be possible ; that is, by the water left in the boiler being, by some impulse,, put bodily into motion, and caused to flow over the over-heated metal. That the over- heating of the sides, to some extent, took place, there is no reason to doubt, although there is great reason to doubt that the quantity of water left in the boiler was sufficient for overflowing entirely the over-heated part, even if such impulse had been given to the mass of water as would have arisen from a slight increase or enlargement of the leak, and which a little increase in the pressure from a more rapid production of steam would have produced. CONCURRENCE OP CIRCUMSTANCES ATTENDING THE FIRST EXPERIMENTAL EXPLOSION. Now let us examine what changes of circum- stances were made at the second trial with the iron boiler when, at last, an explosion did " occur/' The Ee- port states that the boiler was "replenished with water," and we may safely infer that it would not be scantily 142 INCIDENTS OF AMERICAN EXPERIMENTS. replenished, seeing the Committee considered the pre- vious deficiency to be the cause of the failure of the first experiment, or, at least, one cause of its requir- ing to be repeated. Then the boiler was " settled lower into the fire, which was again urged," and the whistling sound of the steam through the leak, which before had increased, " seemed constant." Soon after this, the explosion took place. Here we cannot fail to remark, that the two main circumstances, contributing to bring about the explo- sion, the pressure and the low water, were present in the same degree, or nearly so, as on the first trial ; although the pressure might be a little higher, and therefore calculated to produce, as it certainly did produce, an enlargement of the leak or fracture in the riveting ; which enlargement, in its turn, became the third or actuating circumstance which, concurring with the other two, caused the explosion of the boiler to take place on the second trial. The reader who has followed me thus far, will now be in a position to enable him to make a practical application of this reasoning to the case in hand. PRACTICAL CONCLUSIONS ON EXPLOSIONS. 143 PRACTICAL APPLICATION OF PRECEDING PRINCIPLES. Settling the boiler "lower into the fire/" be- sides raising the pressure of the steam higher in the same time, would also, from the increased expan- sion of the over-heated plates, tend to diminish the leakage, thus diminishing the waste of water and lowering the water-level more slowly, consequently giving more time for the sides to acquire an undue degree of heat from the nearer proximity of the fire. The proved effects arising from overheating the sides, or other parts of a boiler, to a temperature of from 400 to 500, are now well known to be first, the repulsion of the water from the overheated sur- face, producing a decreased amount of steam; but immediately afterwards, as the temperature of the metal is reduced down to the point of maximum vaporisation, or a little below 40 0, by any thing causing the water to flow over the overheated parts, a sudden and greatly increased production of steam. Now, had there been a safety-valve attached to this experimental boiler, and had it been suddenly opened either by the pressure of the steam or by design, this 114 PRACTICAL CONCLUSIONS ON EXPLOSIONS. flowing of the water over the sides would have taken place, according to the theory here enunciated, pre- cisely in the same manner as it was in reality produced by a sudden enlargement of the leak or defect in the riveting ; and from which the rent or rupture of the whole boiler might have proceeded instantaneously. The enlargement of the leak in this case, which a slight increase of pressure was sufficient to effect, may in fact be compared to the pulling of the trigger of a gun overcharged, and ready to go off. Thus also, according to my views, a good safety valve, if brought into action, would have accelerated the explosion of this boiler, or rather have caused it to take place during the first trial. The opening of any ordinary induction valve for blowing through, for the purpose of starting an engine, or any other sudden liberation of the steam, from any cause whatever would have had the same effect. Any thing in fact tending to a disturbance of the equilibrium, or level of the water inside the boiler, would have answered the purpose. This disturbance we are bound to believe was effected by the rending of the boiler at the leaky or defective seam of rivets on the second trial, which caused the rise of the water level over the hot metal, and a con- sequent sudden production of steam, by which the explosion of the boiler was finally produced. SPHEROIDAL CONDITION OF WATER. 145 RECAPITULATION. Respecting the peculiar phenomena relating to the repulsion which takes place between highly heated metal and water, known of late years, as the " sphe- roidal condition of water," and which I consider one p.f the corner stones of my theory of explosions I shall speak more at length in another place."* At present it will suffice to recapitulate the circumstances already mentioned as among the most prominent causes of boiler explosions. First, The overheating of the boiler bottom or sides, or the tops of the internal flues or furnaces, which may be brought about by the water level becoming accidentally too low. The bottom of the boiler, however, may become overheated from many causes without any undue depression of the water level. One is the interposition of indurated sediment, furr, or scale, between the water and the metal. Another is the operation of a powerful blast or draught through the fire, by which such a quantity of steam is generated over a small portion of the boiler bottom, that the water is partially or wholly driven * See Note B at the end, on the " spheroidal " condition of water. 146 DEFECTS OF CONSTRUCTION. away or repelled therefrom, in the " spheroidal condition" referred to; and is often produced by currents of air for smoke-burning purposes, admitted in an injudicious, direction. Secondly, The giving way of some small portion of the boiler, which would not of itself constitute an explosion, but which would be sufficient to liberate a large quantity of steam or water, and create a sudden disturbance of the water level, which circumstance, concurring with the other conditions named, a sudden rise in the pressure of the steam would result, and an explosion ensue. DEFECTS PECULIAR TO BOILERS COMPOSED OF RIVETED PLATES. Ordinary observers sometimes make the re- mark that, in comparison to the frequent instances of boilers bursting, we seldom hear of the bursting of guns; and among sportsmen, never perhaps unless overcharged. Without noticing the truth of the allegation, which is perhaps not quite admissible, there is one circumstance which renders the compari- son unfair towards the boiler. A gun, a fowling WEAKENING EFFECTS OF RIVETS. 147 piece, for instance, though said to be in constant use for a whole day, is only subject to pressure for a fraction of a second at each discharge, not in all occu- pying many minutes, -whereas the boiler has to resist the pressure, and its variations continuously. The general cause of the explosion is the same in both cases. The boiler like the gun is too weak for the charge it contains at the moment of the explosion. " Why then," it will be objected, " can you not do as the gunmakers do make your boilers stronger, with an ample margin, for covering errors of calcula- tion, and unseen defects in the material ; and then, after a double or treble proof, ought not a boiler to be as safe at least as a gun ? " This semi-military way of putting the question, is the language, and conveys the notions, not of military but of many civil engineers and boiler makers of the highest practical talent, and therefore deserves a categorical answer. In the first place, putting out of consideration cast iron boilers, because they are now seldom or never used, although much might be said in their favour, I answer that a boiler composed of plates of wrought iron rivetted together, and overlapping each other at their edges, is in a very different condition to a gun or cannon composed of one nearly uniform piece of 148 WEAKENING EFFECTS OF RIVETS. metal. The latter quickly acquires a uniform tempera- ture after any disturbing cause, and a more uniform contraction or expansion throughout its whole sub- stance is the result. The boiler, however, is neces- sarily exposed to much greater inequality and extremes of temperature ; it is consequently liable to corres- pondingly greater variations of expansion and con- traction ; and it will not be difficult to show that the great contraction and expansion of this compound and complicated structure of plates and rivets forming the boiler, and which is going on continually while the boiler is at work, as necessarily tends to tear it in pieces, even without much assistance, from the pressure of the steam. As an example, in order to illustrate the destruc- tive effects produced by the continually varying expansion and contraction going on among the plates of a riveted boiler, I may take the common case of one 20 feet long by 6 feet diameter, with the fire under its bottom, and containing an inside tube or flue. Both boiler and flue being composed, as is usual, of, say 10 rings of plates of about 2 feet long each. Now, on the first application of the fire to the bottom of such a boiler, and before there is any EXPANSION OF EIVETED JOINTS. 149 ressure of steam at all, each of these plates imme- diately acquires some intermediate temperature between that of the fire outside and the water inside the boiler. These two temperatures may be fairly considered to average about 1500, and 100 degrees respectively to begin with. The external surface of the wrought iron plates where single, and the whole substance of the outside portion of the plates where double or lapped over the other, tending to the higher, and the inner surface of the boiler bottom tending to the lower temperature. The consequence of this is that the expansion of the outer, exceeding that of the inner surface, the boiler bottom becomes to some extent convex outward, or towards the fire in a longitudinal direction; thus, FIG. 5. The curvature of the plates is purposely exaggerated in this figure in order to show more clearly the form the boiler bottom tends to assume theoretically, and not its extent ; on the application of the fire every time the steam is to be got up; and this on the assump- 150 IRREGULAR AND THEREFORE INJURIOUS. tion that the joints of all the plates are perfectly and firmly riveted,, and each plate of exactly equal strength throughout. This however may be considered an almost impossible condition in practice. There is always some one or other of the seams of rivets less capable of affording resistance to the immense force of expansion than the rest, and these parts will there- fore be the first to give way. The consequence is that the boiler bottom more generally assumes the form represented in Fig. 6. FIG. 6. Should there be any pressure of steam at all in the boiler, and the plates be of equal strength, and equally acted on by heat, of course the point of greatest depression would be near the middle of the length of the boiler. The greatest heat, however,. SUBSIDENCE OF BOILER BOTTOM. 151 being in the vicinity of the fire-bridge, is sufficient to determine the position of this point at the nearest seam of rivets to the bridge ; and there in fact this depression is usually found. When permanent, it is then commonly said by the stoker, " The boiler bot- tom has come down." * * Although this expression is usually applied to waggon- boilers, the case is in point of fact one of collapse, similar to that of a large fire-tube of a Cornish boiler. The subject is treated on more at length in my " Essay on the Boilers of Steam Engines," 1839, page 241. As this work has been several years out of print, I give the following extract from a second edition, which I have had some time in preparation, together with an additional volume of " Notes and Illustrations." " It may be asked, if our theory of steam boiler explosions be correct, how it is that we have not many more of them, as the causes to which they are ascribed may seem to be of almost every-day occurrence ? The answer is, that the bursting of boilers is also a matter of every-day occurrence, to an amount which the public generally are altogether ignorant of. To be sure these burstings are not generally called explosions, although in reality they are so, being different only in degree. It would not be difficult to prove that two or three of these minor explosions occur in Man- chester every week ; but when no fatal consequences ensue, 152 SUBSIDENCE OF BOILER BOTTOM. With respect to the extent of the depression liable to be produced from this cause. If we take the differ- ence of temperature between the external and internal surfaces of the boiler bottom, at 500, and allow- ing iron to expand at "00007 of its length, for every 10 of Pah., or -00007 X50=-003'5 of its length for 500, this will correspond to '84, or nearly an inch of expansion in the total length of the boiler bottom externally. The immediate action of the fire is, of course, to bend each plate separately, supposing the latter to be and no particular damage is done to any adjoining property, of course the circumstance never gets into the newspapers, and no public notice is taken of it. " Usually, the affair has quite another name when it occurs with a waggon-boiler ; it is then said that the " boiler bot- tom has come down ; " in other words the concave bottom is forced down into a convex form, and sometimes the sides are in like manner forced outwards, about the middle of the length of the boiler. The consequence in the least violent of these cases is, that the boiler is lifted up a few inches from its seating by the bottom striking upon the top of the fire- bridge. We also usually find every seam of rivets violently strained, so that the water runs through the boiler-bottom like a riddle, although there is seldom a hole of more than a few inches in area. " R. A. DAMAGE CAUSED BY INCRUSTATION. 153 clean. But a boiler has commonly some sediment deposited from the water, and any of the ordinary deposit, however thinly spread over the bottom of the boiler, being a very bad conductor of heat, per- mits the temperature of the plates to rise higher, extending through their whole thickness, and ex- panding the plate, in some cases, to double the amount supposed above. This condition greatly modifies the heat in bending the plates, which become more extended in length, and it adds considerably to the curvature of the boiler bottom. Accordingly, we constantly find, at particular times, a very serious deflection of boiler bottoms downwards at about the middle of their length. The depression commonly admits of accurate measurement, to the extent of a quarter of an inch or less, by placing a loose brick on the top of the bridge, just a little out of contact with the plates. And it regularly takes place in all boilers, to a greater or less extent, every morning before the steam is up, and before there is any pres- sure whatever, excepting what arises simply from the weight of water in the boiler. Yery little observation will convince any one that the peculiar action I have been describing really takes place. The fact is notorious that all boilers are more 154 UNEQUAL EXPANSION, A CAUSE OF LEAKS. or less leaky when the fire is first applied to them for getting up the steam ; possibly the leak is so minute, in some cases, as to be scarcely discernible ; but, generally, the leakage is sufficiently apparent when there is a clear fire under the boiler. Now it is well known that, so soon as the water inside the boiler becomes heated, the leakage de- creases, and, by the time it is boiling, and the steam begins to rise, every leak in the boiler bottom, except those that are running a full stream, is stopped, or nearly so. The cause is, clearly, that the heat, so soon as ebullition in the water commences, is carried off, by the formation of steam, from the inner surface of the plates, as rapidly as it is transmitted through them from the fire ; and therefore, the temperature of the plates falls, or becomes uniform and, consequently, they again assume their original dimensions. The usual expression of the stoker then, is, that the leaks have " taken up," and by the time the steam is up, or sooner, the boiler is " as tight as a bottle." It is, however, the boiler bottom that is " taken up " by contraction and an equalization of temperature on each side of the plates. I am aware that this result is commonly ascribed to sediment being driven into the joints of the plates by the pressure ; but the stoppage LEAKS CEASE WHEN STEAM GETS UP. 155 of the leaks commences before the steam is up, and the same phenomenon occurs in boilers which are quite new, and which contain no sediment. So far as a leakage of the kind just described may diminish the quantity of water in a boiler, it is obvious that it will be generally inconsiderable. A constant daily repetition of this process, however, causes much oxidation of the iron in the vicinity of the leaks, and induces weakness in some particular direction across the boiler bottom, which ultimately causes large open- ings between the plates, and, then, great loss of water results. And how the sudden loss of a large quantity of water in a morning, or at other times, before the steam is up, is likely to end in a violent explosion, at or about the time the engine starts work, will be sufficiently apparent from the explanations already given. HOW CHANGE OF FORM PRODUCES FRACTURE. It is evident that a greater amount of expansion and contraction will be produced at those joints of the plates which are immediately over the hottest parts of the fire than elsewhere. Suppose, for the present, that the whole of the plates in the boiler 156 STRAINS PRODUCED BY EXPANSION. bottom are heated uniformly ; then, since the ends of the boiler are firmly braced to each other by means of the internal flue-tube, as well as by the upper half of the cylinder, neither of which are so much affected by the fire, it is clear that the expansion of one part of the boiler is resisted by the other part. The Ib a FIG. 7. greatest strain from the expansion of the boiler bot- tom will be at the angles A and B (Kg. 6.) at % which points, the rivets (if immoveably fast in the angle- iron) must have a tendency to bend outwards frem the longitudinal thrust of the plate in that direction, as in Kg. 7, which is an enlarged representation of STRAINS PRODUCED BY EXPANSION. 157 the angle B in Kg. 6. The plate will also, some- times, act as a lever in wrenching off the head of the rivet ; or, as usually happens, by successive opera- tions of this kind, the rivet-holes in the plates become permanently enlarged, and break out. For example, so soon as the water becomes sufficiently heated to cause ebullition to commence, however slightly, the temperature of the plates immediately falls to 212, or to such a degree as corresponds with the boiling-point at the time. And this point being attained, of course, contraction of the bottom-plates immediately ensues, as before described, co-equal with the previous expansion. The thrust at the end rivets now becomes a drag in the contrary direction, or as shown by the position of the lines aa and &&, in Pig. 7, which represent the directions to which the varying position of the rivet respectively inclines, according as it is acted on by the expansion or the contraction of the boiler bottom. If the rivets do not always give way, they enlarge the rivet-holes, which, by this alternating action, become oval or lengthened in the direction of the strain and, ultimately, cracks are formed between the rivet-holes and the edges of plates as shown in Pig. 8, which is a plan or top view of Pig. 7. 158 STRAINS PRODUCED BY EXPANSION. One object I have in view here is to show that severe strains upon the rivets of a boiler, arising from undue expansion and contraction, may be increased by the thickness of the plates, and that the destruction of boilers from that cause is not confined to those formed with angle irons and flat ends, but extends also to those made with hemispherical or "egg" ends, which are ordinarily considered superlatively safe high pressure boilers. Such boilers are usually of less diameter, and are consequently of greater length, on which account they are more particularly obnoxious to the defect I have been treating of, arising from a proportionately increased amount of expansion and contraction. EXPANSION PRODUCED BY HOT BRICKWORK. 159 As a practical example, I shall conclude by de- scribing a boiler of this kind which came under my observation a few years ago in London. This boiler was 3^ feet diameter by 30 feet long, and set up with the ordinary wheel draught which is a very common, though a very improper mode of setting a boiler of so small a diameter. The conse- quence was that in order to obtain sufficient space for draught in the side flues, the brickwork had to be carried up considerably above the centre, and the boiler was finally covered over with brickwork; a dangerous practice though extremely common. The reason for covering boilers in this way is of course to retain the heat, which it certainly does, but such a covering may be very detrimental to the durability of the boiler. Thus, when the fire is under the boiler, the temperature of the boiler bottom may not generally be more than about 250, while that of the side flues cannot be less than 500 or 600 degrees, and the brickwork resting on the top of the boiler is seldom less than 350 or 400, as I have frequently ascertained, and of course the iron in con- tact with it will be of the same temperature, except so far as the heat is carried off by the steam in con- tact with the metal. Now here may easily be a 160 EXPANSION PRODUCED BY HOT BRICKWORK. difference of 200 or 30 0, causing a considerable amount of expansion in the top of the boiler, and a corresponding strain upon the rivets in the boiler bottom. But supposing the boiler to be emptied by running out the water at the end of the week for the purpose of cooling and cleaning it out, or of cleaning the flues : and further, for the purpose of cooling it quicker, suppose that a quantity of cold water is immediately run into the boiler, and let us see the extent of the evil which takes place then. The hofc brickwork will retain the upper half of the boiler, upon which it rests, at full stretch ; while the lower half, at least so far as the cold water extends, sud- denly contracts, and instead of 200 we may have a difference of 400 p between the top and the bottom of the boiler, equivalent to about an inch in the whole length of the boiler. As near as could be judged, on close examination, this was the precise extent to which several openings in the seam across the boiler bottom amounted to collectively. One or two of the dislocated parts becoming jammed, and retaining their positions per- mitted of exact measurement.. This gradual disintegration of a boiler has no doubt been frequently observed by others, although not INJURY FROM COOLING BOILER. 161 remarked upon. This particular example occurred at a factory where it was the custom to clean out one of the boilers every Sunday morning; for which purpose the stoker commonly filled the boiler he intended to clean immediately after letting out the hot water. And the case is adduced as an example of those cases where for years very great expenses were incurred in repairing and remaking the boilers without the cause of the defect having been discovered. Since, how- ever, that practice of filling the hot boiler with cold water has been discontinued, although the boilers are now of thinner iron, larger diameter, and worked at higher pressure, a boiler-mender is scarcely ever re- - quired on the premises. 162 NOTE A. ( TO PAGE 137. ) EXPLOSION AT BROOKES's FLAX MILL, BOLTON, JULY 1ST, 1844. Although some of the conclusions arrived at in the American Report may admit of exception, evi- dences tending to corroborate the general accuracy of the committee's observations ought not to be with- held. So far as two or three instances of explosions go, I have had an opportunity of witnessing those appearances, which, to my mind at least, confirm the description given by the committee. As one example, I may refer to the explosion of a large boiler at the flax spinning mill, belonging to the late John Brookes, Esq., in Little Bolton, Lancashire, which I personally witnessed at the distance of about 300 yards from the mill, to which I was then on my way, when the accident took place. First, a column of dust arose to a considerable elevation, in which some of the timbers of the roof of the building, which enclosed the boiler, were seen flying in different directions ; then arose a cloud of NOTE A. 163 smoke, which spread out above in a large black canopy ; through this a column of steam and water shot up to a very great height, which dispersed in mode- rately large drops, like a slight shower of rain in the direction of the wind, and to the distance of about 4 or 500 yards from the mill. At the same time, as a column of steam continued rising from another boiler in connection with, and nearly adjoining the one that burst, for about half a minute, and as the lower part of the cloud of smoke and dust began to clear away, flames commenced making their appearance, arising from a high building ad- joining that which had been blown up along with the boiler; and which, in fact, as I afterwards found,, had been set on fire by the burning coals from the furnace of the exploded boiler being driven in through the windows of the lower story of the building. The boiler was of the waggon form, about 27 feet long by 9 feet wide, and 10 feet deep, weighing pro- bably about 10 tons, and called 40 horse power. The lower portion, reaching up to the top of the side-flues, about three-fourths of the whole, was thrown in a single mass to about 20 yards from its seat ; while the upper or semicircular portion, together with the steam-pipes, safety-valve, nozzles, and other 164 KOTE A. attachments, were thrown to a great height, and fell in the adjoining street, the ground of which was at an elevation of more than 20 feet above the level of the seat of the boiler. The circumstance in which this Bolton Explosion differed from those in the American experiments, is remarkable, that is, in the report or sound produced. For if the report produced by the bursting of a very small boiler, only 10 inches long by 8 inches in diameter, was like that from the discharge of a cannon, what might we not expect from the explosion of a boiler 27 feet by 9, or about 5,000 times larger. But the fact is, that neither myself nor a friend, whom I was in conversation with at the time, heard any report of that kind at all, bat only a rumbling sound such as might be supposed to arise from the cracking of the roof-timbers, the falling of the building, and the blowing-off of the steam from the other boiler, which had been working in connection* with the one that exploded. There was a low continued rumbling noise, as described by some who were nearer to the scene of the explosion when it commenced, but it was certainly not loud) and, indeed, scarcely audible to us at the distance before mentioned, although our attention was particularly directed to the cloud of NOTE A. 165 dust and smoke which arose from the mill. It being not a little remarkable also that the subject of our conversation at the time was the deterioration to boilers from incrustation, and increased liability to accident from working higher pressure, which had then recently been adopted at this very mill, on account of attempting to work the engines more expansively on the Cornish system, but without the strong Cornish boilers. The destruction in this particular case, in my opinion, being greatly increased by using Mr. Williams' s patent system of smoke-burning, which required the keeping of a thick fire (over 18 inches), and a stream of cold air passing up behind the fire-bridge. The area of the fire-grate of the exploded boiler was about 60 square feet, consequently it was charged at the time of the explosion with nearly 100 cubic feet of burning fuel. The effect of the sudden dispersion of such a mass of fire may be easily conceived. That portion of the boiler-bottom which extended over the fire-place, about 3 feet square, was torn right across, nearly in a straight line from side to side, exactly at the position of the bridge, besides being ripped up on one side through the seating-plates, and across the front end at the angle over the fire-door ; thus this large portion, being libe- rated on three sides simultaneously, it was doubled 166 NOTE A. back on the other seating, as on a hinge or lite the flap of a table, thereby opening out a hole of about 60 square feet in area, with an initial pressure of steam at about 201b. per square inch. And immensely reinforced as that pressure would be by contact with the burning fuel in the furnace, it is not difficult to divine the great force of the explosion, and the con- sequent disastrous results that followed. My first impression, on witnessing the commence- ment of the scene just described, was that it was the breaking out of a fire, and that, indeed, was the general impression of great numbers of the people in the streets of Bolton, who were making their way to the scene of the catastrophe, until met by the crowd of operatives, rushing out of the gates of the factory- yard, many of them cut and bleeding from the effects of the broken glass windows, which had been driven in upon the workers in several rooms of a six-story building, situated close to the boiler-house. It was through these windows that the burning coals from the large furnace were principally driven, which set on fire the machinery inside the mill, where the conster- nation and rush to escape was very great, as may easily be supposed, there being in the whole factory about 540 people employed at the time. NOTE A. 167 Eespecting the peculiar sounds or reports pro- duced by boiler explosions, it may be stated that the strangest discrepancies occur in the statements of pro- fessed eye and ear witnesses of this and similar explosions. For instance, in this case, more than one party testified to having heard the report more than two miles off, like that from the discharge of an immense piece of ordnance. All the London papers, true to their character of exaggerators of everything, had it, that the people of Bolton were suddenly startled as with a loud clap of thunder ; and some of them stated that the whole town was alarmed as with an earthquake, an opinion which the country papers also shared, after the London news- paper reports reached them. B.A. 168 NOTE B. ( TO PAGE 145. ) The term "spheroidal" was, I believe, first applied some years ago to that particular condition water is in when repelled from a hot surface in the form of roundish drops, by Mr. J. E. Bowman, then Pro- fessor of chemistry at the Royal Institution, Man- chester, and since of King's College, London. This was on the occasion of his reading a lecture on the subject of steam boiler explosions, in the above institution, in the course of which he was the first, perhaps, in this country, to give an account of, as well as to show experimentally some of those remark- able properties of water and other liquids when pro- jected into red hot vessels, since made popular by some curious performances at the meetings of the British Association, and more recently at the British Institution, by M. Boutigny, of Evreux, in Prance. This gentleman, who had been some years engaged in the prosecution of researches connected with the NOTE B. 169 subject, was, until the delivery of Mr. Bowman's lecture, above referred to,* and its subsequent publi- cation, generally supposed to be the first who had attempted to " account for explosions on the suppo- sition that water in them passes, under certain cir- cumstances, into the spheroidal state." Sufficient evidence, however, was furnished to Mr. Bowman on that occasion, that I had been many years well acquainted with the principle of the spheroidal con- dition of water in boilers, its tendency to create priming and to promote explosions, although I had never thought of giving it that or any other distinc- tive appellation. That I had several years prior to its, no doubt independent, discovery by M. Boutigny, also applied it to account for some of the explosions of steam boilers, was a fact which Mr. Bowman very handsomely acknowledged both in his lecture, which was followed by a public discussion on the subject, and also in his pamphlet, by quoting at length pas- sages containing evidences thereof from a pamphlet of mine, published in 1836-7. An instance of libe- * " On some remarkable properties of water and other fluids, with reference especially to the causes and prevention of steam boiler explosions." By John Eddowes Bowman. London : J. W. Parker, 1845. 170 NOTE B. rality and justice so honourable, though rare, among scientific writers, that I cannot omit this opportunity of publicly acknowledging it. And I may here notice the fact that, although partly printed in 1836, my book was written and the manuscript perused by several friends nearly three years before that time. The complete application of the discovery to the theory of explosions was in reality made by me pre- vious to 1830, when, in conjunction with my then partner, Mr. Henry Wright, engineer of Manchester, I made application for a patent, embodying the prin- ciple of the repulsion of water from over-heated boiler bottoms and front tube-plates of locomotives, being one cause of the priming of steam boilers, as well as causing explosions. During the years 1831 and 1832, it is quite notorious, in Manchester, that I frequently exhibited the principal experiments relative to it, in explanation of the bursting of boilers. Small glass boilers were purposely exploded with that view in the presence of well known parties in numerous in- stances. The simplest mode in which those unused to ex- perimenting may most conveniently at any time readily demonstrate the "spheroidal condition of water/' is that of heating the bowl of a large tea- NOTE B. 171 spoon over the flame of a candle until water runs off without wetting it. Then, by the aid of a dropping tube, or a quill, or any other means of measuring into the spoon successive drops of water of the same size, the leading facts of the repulsion of liquid in the form of beads or spheroids become very apparent. Thus a moderately small-sized bead or globule of water, when the spoon is very hot, will be observed to rotate rapidly on its axis, all the while moving quickly about, supported by a thin film of steam, and occupying half a minute or more perhaps before it is entirely evaporated. If now, without reheat- ing the spoon, and while, in fact, it is rapidly cool- ing, we place another drop of water of exactly the same size in the same position as the first, it will, after assuming the same spheroidal appearance, rapidly diminish in size, and evaporate entirely away in two or three, or, at most, in a very few seconds. A third drop so placed will be found generally to disappear in less than one second; or, if the experiment be carefully managed, the last drop will be made to vanish instantaneously and without assuming the globular or spheroidal form. The temperature of the metal of which the spoon consists will then of course be that of maximum 172 NOTE B. vaporisation, and which is usually found to be considerably under 40 O p Pah. By the American experiments it was found to be about 350, and the temperature of perfect repulsion of drops of water, projected into an iron bowl a quarter of an inch thick was 405. The committee also refer to a series of experiments by Professor Johnson, who places the maximum evaporating point at between 304 and 320 Q , and in their general view of the facts detailed, state that the repulsion between the metal and the water is perfect at from 20 to 40 Q above the point of maximum vaporisation, at which temperatures the water does not wet the metal. Some of the conclusions arrived at by the com- mittee are as follow : 1. The temperature of maximum vaporisation, both in copper and iron, is lower as the surface of the metal is smoother, and the amount of vaporisa- tion in a given time is much diminished. 2. The temperatures of maximum vaporisation,, for copper and iron in similar states of surface, differ between 30 and 40, the iron having the higher point. 3. The time of vaporisation, at the maximum, is less in the copper than in the iron, in the ratio of NOTE B. . 173 about 2 to I, probably, nearly in the ratio of the con- ducting powers of the two metals for heat, which are as 2J to 1. (See American Beport, Page 47.) It must be observed that the above results are from drops, or small quantities, of water, under atmo- spheric pressure only. And, however interesting they may be in a philosophical point of view, they cannot be said to touch the practical question of the effect of large quantities of water brought suddenly into contact with hot metal, in producing explosions. Accordingly, some experiments with cast iron bowls, half an inch thick, containing large quantities of water, placed over charcoal fires, indicated that the highest point of greatest evaporation was placed, at least, about 200 below red heat in daylight, and in the most favourable circumstances, varying from 550 to 600 Fah. for wrought iron, and from 470 P to 526 P for copper. In the course of the experiments of the American Committee, it was observed that, with other liquids, Alcohol for instance, at a certain temperatifcre of the dish, that of the spheroid became stationary at 169iorl70, (theboiling-pointbeingl73) and that it could not be raised higher ; indeed the temperature of the spheroid became lower as that of the dish was 174 . NOTE B. higher. In my own experiments, that point not appearing to me then to have any direct useful appli- cation, I had only generally remarked that the tem- perature of the globule of water must be lower than 212 from the fact that it did not boil. And it is entirely to the delicately manipulated experiments of Messrs. Bowman and Boutigny that we are indebted for a knowledge of the fact, that the tem- perature of a spheroid of water is invariably constant at 205, or 7^ below its boiling-point, however hot the crucible which contains it may be. Thus, also, a spheroid of alcohol always stands at 170 or 3 below its boiling-point ; one of ether is always 5 below, or 95 ; and liquid sulphurous acid which boils at 14, never reaches so high even as that low temperature when in the spheroidal state, but continues far colder than melting ice, even though the crucible in which it lies be all the time at the most intense white heat. It was on this principle that M. Boutigny contrived the feat of freezing water in red hot crucibles, and afterwards that of handling melted cast iron. E. A. 175 APPENDIX, No. I. REMARKS ON SMOKE-BURNING BY JOHN BOURNE, ESQ. [The following remarks form a portion of a review of Mr. diaries Wye Williams' s book on " The Com- bustion of Coal and the Prevention of Smoke chemi- cally and practically considered," which appeared in the " Artizan" for February, 1843.] The smoke evolved by every species of bituminous coal, when burned in common furnaces, must neces- sarily detract considerably from the calorific efficacy of the fire, both on account of the direct loss of a portion of the combustible which passes oft 7 in the form of smoke, and is dissipated in the atmo- sphere, as well as from the loss of the heat re- quisite to convert the hydrocarbons, so dissipated, into the gaseous form. Numerous attempts have been made to obviate or diminish these sources of waste, by admitting into the flue or furnace a stream of air, 176 APPENDIX. to accomplish the combustion of the inflammable parts of the smoke ; but the difficulty of apportioning the quantity of air admitted, to the varying wants of the fire, has been found an insuperable objection in the case of ordinary furnaces ; whilst the refrigeratory effect of the excess of air it is necessary to admit, in order to bring the atoms of the combustible and the supporter within the range of combining attraction, goes far to neutralize the increased heating power consequent on their combination. In experiments upon smoke-burning furnaces, conducted with great care and skill, possibly some little saving may have been repeatedly realized; but with the measure of care and skill which furnaces can obtain in the ordinary routine of practical operation, smoke-burning has invariably been productive of a diminished effi- ciency or an increased consumption. All this Mr. Williams acknowledges ; but main- tains that his is not a smoke-burning, but a smoke- preventing furnace. Smoke, he admits, cannot be burned advantageously ; but it is not smoke, he says, but gas, that he attempts to consume. The difference is certainly conceivable, and not unimportant ; yet, on looking at the construction of Mr. Williams' s furnace, we find that the furnace proper differs in no respect APPENDIX. 177 from common furnaces ; and the aeriform matter which passes through the furnace-throat must, there- fore, necessarily be of the usual description. The whole of Mr. Williams' s plan, indeed, consists in let- ting air into the flue by a multitude of holes ; but the substance to which the air is admitted is identical with that in furnaces of the ordinary kind ; and his furnace is, therefore, just as much a smoke-generating furnace as any furnace whatever. The difference be- tween smoke and gas is simply this : one is the pro- duct of imperfect or incomplete combustion, whilst the other is not the product of combustion at all, but of volatilization merely ; and, as combustion is carried on in this gentleman's furnace, the substances flowing past the diffusion-orifices, which are the product of that combustion, cannot be coal-gas by any possi- bility. The question really at issue is not whether it is beneficial to admit air to gas in one hole or in many holes, but whether, in the case of this furnace, it is gas at all to which the air is admitted. To pretend that smoke can be turned into gas, by letting in air upon it by one hundred holes instead of by one or two, is just as preposterous as to maintain that the plant which, when watered with a common watering- pot, is a lily, will be turned into a thistle if watered H 178 APPENDIX. with a jug. In spite, then, of all the indignation Mr. Williams has heaped upon "smoke-burning preten- ders/' it is, in our eyes, undeniable that he is himself one of the genus he so loudly condemns ; and as we participate to a certain extent in his disapproval of smoke-burning expedients, we are compelled to sur- render him to his own reprobation. The ineffectual and injurious character of Mr. Wil- liams' s arrangements are, we think, very ably pointed out in a report of Mr. Armstrong's addressed to a Respectable manufacturing firm in Manchester, and in- serted at p. 102 of the present work. In answer to this statement, Mr. Williams contends that when there is no smoke to be burned, there is carbonic oxide, and that therefore a rush of cold air through the diffusion orifices, at any time is impos- sible. But if the furnace be made to produce carbonic oxide in considerable quantity at all so as to combine with the oxygen when there is no smoke, this carbonic oxide must pass off unconsumed where there is smoke, provided the smoke be consumed, and a great waste of fuel must thereby be occasioned. In the case of ordinary furnaces, it appears impossible indeed for Mr. Williams to extricate himself from this dilemma ; he must either have a current of cold air rushing at times through the APPENDIX. 179 diffusion orifices, cooling and injuring the boiler, or large quantities of carbonic oxide continually escaping into the chimney, so as to occasion a material waste of fuel. On the whole, it appears to us that although this project may be capable of affording some satisfac- tion so long as it meets with the care due to a novel and nurseling project as, indeed, a host of previous schemes have repeatedly done yet that in the aggre- gate of ordinary working, it will approve itself trou- blesome, expensive, and pernicious. Of Mr. Williams' s book, our verdict, we fear, must be as unfavourable as of his invention ; yet it has re- ceived high praise in various quarters ; and although its admirers are not the best sort of admirers, we doubt not their panegyric has been accepted by Mr. Wil- liams as good sterling praise, and will probably render distasteful any more discriminating analysis. Indeed* the expectations of any author who has once tasted of popular applause, are by no means easily satisfied. Upon his first appearance before the tribunal of public opinion, he will generally be content if he escape without censure ; but his expectations rise with his success, and the judgment he would at first have ac- cepted with joy and gratitude, he will speedily come to look upon as prejudiced and disparaging. Upon any person, indeed, prominently before the public, a 180 APPENDIX. word of disapprobation falls with prodigiously in- creased weight : so long as he remains in obscurity, reproof is unattended with disgrace because it is ne- cessarily unwitnessed, but the crowd he brings around him by Ins triumph, if it adds to the brilliancy of success, fearfully aggravates the penalties of failure. Every voice which swelled the measure of his fame will add to the ignominy of his degradation ; and a measure of praise which would have exceeded the hopes of his earlier ambition will now only suggest humiliating ideas of his unfitness for the position he has so incautiously usurped, and the derision and dis- appointment his incapacity has excited. An inquiry into the phenomena attendant upon the combustion of coal divides itself into two parts. First, The determination of the chemical constitution of the coal ; and, Second, The determination of the quantity of air requisite for the combustion of its constituents. Mr. Williams has gone into both of these subjects at considerable length. He has given us a compilation of authorities showing what the chemical composition of different species of coal is, and has favoured us with several chapters and a mul- titude of diagrams to point out that carbon and hydrogen combine with oxygen in definite proportions. APPENDIX. 181 In the whole of these most ingeniously constructed chapters, there is not a single remark of the least worth or moment; and in the whole length and breadth of the book there is nothing new, except its errors and the magisterial solemnity with which the most trite and insignificant truths are reproduced and paraded. Indeed, Mr. Williams seems very fond of burning his gas in the blaze of noon-day. He de- votes pages to prove self-evident propositions, and takes infinite pains to convince sceptics of things no- body ever thinks of doubting. He continually speaks of atoms as if he himself had found them out, and as if an introduction to so difficult a theme inspired ex- traordinary trepidation ; as in page 40, for example ytere he encouragingly tells us " not to feel alarmed at this introduction to elementary atoms and chemical equivalents." In pages 27, et seq,, the discovery is announced to us, that when fresh coal is thrown upon a fire, the fire is afterwards not quite so hot as before ; in pages 28 and 29, we are assured that heat is neces- sary to expel gas from coals ; in page 35, that a com- bustible as well as a supporter are indispensable to combustion; and in page 37, that the combustion of gas is accomplished, "not by its combination with the .air, as is the vulgar and dangerous notion, but with 182 APPENDIX. the oxygen of the air the supporter of flame the heat-giving constituent of the air." In page 91, we are told, " Without sufficient time, nothing short of a miracle could satisfy the required extent of diffusion- Nature, however, does not operate by miracles, but by defined laws and progressive means;" and in page 129, we are assured that combustion cannot take place without air ; " that providing heat is not pro- viding air, neither is decomposition combustion." In page 11, we are told that Sir Humphrey Davy was an eminent man; in page 20, that Dr. Faraday is the first electrician of the day ; and in page 41, that John Dalton is a writer of merit. At page 70 commences a chapter of 30 pages for the purpose of pointing out that as it is oxygen which supports the combustion is a furnace, the air supplied to the furnace must not have been deprived of its oxygen previously, else it will not do : for thus wisely and thus learnedly ar- gues this philosopher, " If oxygen be not present in the air, how can it otherwise be obtained ? How can we effect a union with a thing which is not?" In extenuation of the marvellous superficiality of this gentleman' s treatise, it may, perhaps, be urged that he wrote not for scientific, but for practical men. This argument might, perhaps, have some weight if APPENDIX. 183 by practical men were meant our working boiler smiths and bricklayers, who for the most part are supposed to know as much of chemistry as of the (Elic redupli- cation ; yet, even in this case, we do not altogether see how those persons should be induced to read this book more readily than some of the numerous chemical works to which they already have access. Mr. Wil- liams, however, informs us that he does not address himself to so unpromising an auditory, but to those by whom engineering works are directed and designed. ' Are then our bricklayers or boiler-makers to become chemists? No. But those who direct those who assume the charge of teaching them to construct the numerous descriptions of furnaces with which this country abounds, should be masters of the leading principles on which their art is based, and the success of their operation depends/ of which it would appear they at present know nothing. Thus in page 2, Mr. Williams informs us, that, even the most experienced engineers know very little about the boiler in page 3, that in the construction of boilers engineers are without any fixed principles to guide them in page 4, that he has watched the efforts of engineers to arrive at some degree of certainty, and that he has perceived the absence of any intelligible or well-founded prin- 184 APPENDIX. ciple in the boiler in page 5, that instead of improve- ment there has been latterly retrogression, and that well-established houses even yet know very little of the principles of perfect combustion, or of the economy of fuel. Prom these and numerous other passages, which might be cited, it would appear to be this gen- tleman's doctrine that engineers are a very ignorant and stupid race of persons ; that though living in England in the nineteenth century they are unac- quainted with the simplest and most familiar truths of chemistry ; and while possessing the reputation of producing those miracles of ingenuity which carry their fame to the verge of civilization, that they exist in a state of mental stupor which the most besotted Turk could scarcely hope to emulate. A person, in- deed, who derived his only information on this sub- ject from Mr. Charles Wye Williams, might imagine our mechanists to be the descendants of some barba- rian horde on whom a hereditary curse rested, doom- ing them to an eternal degradation ; who remained rude and untutored even in the centre of civilization, and whom the flame of science could neither melt nor quicken, nor the lessons of experience instruct. It is not astonishing, therefore, that Mr. Williams should speak with much confidence and coolness of the ab- APPENDIX. 185 surdities of the practice of our engineers, which in pages 34, 72, 73, 74, 127, and, indeed, in almost every page throughout the volume, he most indus- triously exposes. He takes especial care to make manifest the shallowness of Tredgold, and the erro- neous notions of Watt, which he of course contrasts with his own higher skill and superior illumination, and finding himself unable to refute what they do say, wisely confines his refutation to what they do not say. In page 134, he states, 'the erroneous view of the combustion of the gases began with Watt / but after handling poor Watt very severely for his manifold shortcomings, he kindly winds up in the following patronizing strain: ' But let justice, however, be done to Watt. It is not his fault that the errors he com- mitted should continue to be repeated/ which our present engineers are, it appears, wrong-headed enough to do. The following epithets are therefore unsparingly applied to the practice of those obdurate persons ; f erroneous/ e lamentably erroneous/ f neglect of chemistry/ 'notable instance of neglect of chemistry/ 'abortive attempts/ 'great practical and chemical error/ 'palpable oversights/ ' unsound principles/ 'chemical blunder/ ' utterly at variance with chemical propriety/ and a host of other equally decorous and appropriate 186 APPENDIX. expressions. The secret of all this we suppose is, that Mr. Williams plumes himself not a little upon the smattering of chemistry he appears to have acquired, and in the simplicity of his heart imagines that be- cause our leading engineers do not think it consistent with their dignity to become lecturing itinerants, or to be eternally flashing their attainments in the eyes of ignorant spectators, they know nothing of the most familiar scientific truths, and -pay no regard to them in their practice. If Mr. Williams could only see himself as he is seen by others if he could only per- ceive the ridicule he draws upon himself, by harping everlastingly about chemical principles, and chemical blunders and which we can assure him raises the secret laughter of even the most favourably affected he would, we are sure, gladly retire into the obscurity for which Providence manifestly designed him, and leave the contention for distinction to those who have something better to offer as credential than a flood of scientific jargon, or the pitiful pedantry of a boiling empiric. J. B. 187 APPENDIX, No. II. AMERICAN EXPERIMENTS ON EXPLOSIONS, Made by order of the Treasury Department of the United States, in which, among other instructions on the subject, directions were given. " To observe accurately the sort of bursting produced by a gradual increase of pressure within Cylinders of Iron and Copper. " It has been contended by some, that ruptures pro- duced by a gradual increase of pressure within steam boilers do not bear the character of explosions, but that a mere rending takes place, giving escape to the contents. This has been assumed to be especially the case with copper boilers. To make the observation required by the above question, cylinders of iron and copper were prepared, of sufficient size, to make a small thickness of material answer for rending by a pressure which was easily attainable. Two experi- ments made, one with an iron and another with a copper cylinder, afforded so direct an answer to the query that it was not deemed necessary to carry the experiments further, especially as they were tedious, and not without danger. A further experiment of the 188 APPENDIX. same tenor, resulted from a trial of Perkins's assertion in regard to the effect of making an opening in a vessel containing water, and heated to a high temperature. ' ' The boilers used were cylindrical, eight and a half inches in diameter, and ten and twelve inches respec- tively in length, of iron "02 inch thick, and of copper '03 inch thick, having iron heads '05 inch thick, to which the convex surface was fixed by iron rivets, placed nearly touching each other. A single opening in the middle of one of the heads of each boiler was provided to in- troduce the water, and was furnished with a screw, into which to insert a tube and piston, connected with a small spring weighing machine, which is represented at a in the cut on page 124. Upon the cylinder of this machine a ring was placed, which was moveable along the cylinder by a slight pressure : this ring was forced towards the end of the cylinder nearest to the boiler head, as the spring was bent, and remaining in its place when the spring relaxed, served to register the maximum pressure to which the piston had been exposed previous to observing it. "The iron boiler was placed in a heavy cylinder of wrought iron, which served as a furnace, the axis of the boiler being nearly horizontal, and that of the furnace cylinder vertical. The boiler, having been APPENDIX. 189 half filled with water, was placed upon a fire of char- coal, and when the water boiled, the register machine for the pressure was screwed in. " The place selected for the experiments was in a de- serted quarry on the banks of the Pennypack, near Holmesburgh. The high bank served as a protection, by the aid of which the experiments were viewed with little danger. A wire and cord were attached to the head of the boiler, to draw it from the fire when the latter required to be replenished. A leak in the riveting of the iron boiler allowed so much steam to escape that the boiler did not give way on the first trial. As soon as the escape of steam was observed to cease, the boiler was removed from the fire and again half filled with water. The fire was urged, and the boiler settled lower into it, and by once replenishing the fuel, without removing the boiler, an explosion was produced. Part of the committee were engaged in observing the progress of the experiment at this moment. The fire was near the middle line of the boiler, burning not strongly near that line, but very rapidly below the boiler; the steam issued freely through the leak before alluded to, and the whistling sound which it produced, and which had increased gradually in strength as the experiment progressed, 190 APPENDIX. seemed constant. The length of time during which the steam had escaped showed the water to be low, and induced the supposition that a second time the object would fail; when an explosion occurred. The explosion tore off one of the heads, d c, of the cylinder, projecting the other parts of the boiler in an opposite direction, carrying with them for a portion of the dis- tance, the iron cylinder forming the furnace, and scattering the fuel in every direction. The report attending the explosion resembled that from a small mortar (eprouvette) fully charged, the steam mixed with the smoke was not considerable in quantity, and few marks of water were to be seen. The boiler head was thrown fifteen feet, the boiler and spring register about six feet, and the furnace, weighing about forty- five pounds, was overturned and carried four feet. The pressure indicated by the register was eleven and a quarter atmospheres. " In examining the boiler it appeared that the head, 5, which was thrown off, had first struck against the iron furnace, which had deflected it outwards ; this is shown by the indentation, b c, in the figure. This head was forced off all around in the line of rivets which attached the head to the boiler, the metal re- maining between the rivets being less than the space APPENDIX. 191 occupied by tliem. Tlie convex surface and the other head were thrown likewise against the furnace, and the head indented at d e, overturning the furnace and carrying it four feet, as already stated. The boiler finally struck against the side of the bank of earth. The piston of the weighing machine was somewhat bent in the experiment. "The circumstances of this experiment show that the steam rose quite gradually on account of leaks in the boiler, increasing, probably, more rapidly as the quan- tity of water diminished, the intensity of the fire meanwhile increasing. That at a certain period the tension within had attained about eleven atmospheres, when the boiler exploded violently. " The accompanying figure (3) will serve to give an accurate idea of the appearance of this boiler after its rupture. " The cylinder of copper, before referred to, was next put in the place of the iron boiler, and the fire again kindled; the general arrangements being as before described. This boiler being longer than the former would not descend so far into the furnace, and an at- tempt to raise the steam sufficiently high to burst it failed : there was a considerable leak in the junction of the curved surface with one of the ends. When 192 APPENDIX. the water was nearly exhausted, the fire having passed its period of greatest heat, the cylinder was removed and water again introduced, filling about three-fourths of its capacity. A new furnace was constructed of stones, allowing the boiler to rest more closely upon the fuel, and affording a screen from the wind which was blowing quite strongly. The part of the boiler in which the leak had been observed was turned down- wards, but a similar escape was found for the steam in the part now uppermost. The tension of the steam appeared to increase very slowly, and the fire passed its best action without effect ; it was renewed, and as the water became lower the tension of the steam increased considerably. As before, nothing remarkable occurred previous to the instant of explosion, and the members of the committee, employed in the experiments, were engaged in observing the boiler at the instant it ex- ploded. A dense cloud of smoke and flame, capped by steam, rose from the pit ; the stones and combus- tibles were widely scattered, and the boiler was thrown, in a single mass, about fifteen feet from the furnace. The noise attending this explosion was like that from the firing of an eight-inch mortar. " The boiler was rent as shown in the accompanying figure (4), giving way in an irregular line just above the APPENDIX. 193 probable water line on one side of the boiler, but not conforming to it. d and 5 were the lowest points in the two heads before the explosion. The sheet of copper was torn from the heads, nnrolled and irregu- larly bent, adhering to the heads for only a short dis- tance near the top of each ; and the heads were bent outwards. The thickness of the copper along the line of rupture yaries from '025 to *035 of an inch, and the metal appears to have been highly heated at one end of the torn portion. The piston of the spring gauge was bent, the screw which attached it to the boiler broken, and the whole instrument otherwise in- jured ; it appeared that the wire intended to draw the boiler off the furnace had slipped and impeded the action of the piston, so that no register of the amount of force producing this explosion was obtained.* " The circumstances, as before, show that the steam was allowed to rise gradually until the boiler gave way. It is possible that there may be a relation be- tween the space occupied by the water and that in * "Assuming the strength of copper at 36,000 Ibs. to the square inch, and that it was uninjured by the heating, neg- lecting also the effect of temperature, the bursting pressure appears by calculation, to have been about sixteen atmo- spheres. It was, no doubt, less than this." 194 APPENDIX. which the steam is formed most favourable to the production of steam, and that when this was attained a rapid rise in elasticity took place ; but there were no circumstances observed which would confirm such a view., and if it were correct it would only affect the conclusion as far as the increase of tension might have been rapid from such a cause. " As in the former case the marks of the sediments remained in the boiler, and indicated that the water was about an inch deep when the cylinder exploded. Much more steam was formed, and more water left than in the first experiment. " These experiments, together with the one referred to in a subsequent part of this report, are direct and conclusive ; they show that all the circumstances at- tending the most violent explosions may occur without a sudden increase of pressure within a boiler. There can be no doubt, however, that if particular portions of a boiler are much weaker than other parts, they may give way in time to prevent such a catastrophe." (From " REPORT of the Committee of the Franklin Insti- tute of the State of Pennsylvania for the promotion of the Mechanic Arts, on the EXPLOSIONS or STEAM BOILEES. Part I. Containing the first report of ex- periments made by the Committee for the Treasury Department of the United States." Philadelphia, 1836.) CONCLUDING NOTICE. I have been constrained, only by considerations of space, to omit descriptions of several excellent boilers both of the multitubular and flue construction. Among the former are those of ANDREW (locomotive), BAR- RANS (cup surface), BURNEY (river boat), GORDON of Stockport, and HOLCROFT of Manchester. And among the latter are CAMERON'S (upright conical furnace), COWBURN'S (cellular), and DUNN'S (patent vertical), all of which are among the best of their respective kinds. ERRATA. Page Line 44 9 from bottom for " as," read of. 110 6 " " conducted," read witnessed. 124 1 " after "page 66," add^. 187 of this look. 13310 " for " Fig, 4," read Fiy. 3. PRINTED BY G. HATTON ROBEET AEMSTBQNG, C.E. CONSULTING MECHANICAL ENGINEER, BOILER, A.ND FURNACE ARCHITECT, AND SURVEYOR OF STEAM ENGINES AND OTHER MACHINERY, 65, FENCHURCH STREET, LONDON. ME. ARMSTRONG begs to intimate that lie may be consulted on any engineering question at the above address, either by letter, or personally on an interview having been previously arranged. Mr. Armstrong's large experience as a boiler and furnace architect, for nearly thirty years, warrants him in assert- ing that those who consult him, either as to the efficiency, economy, and durability of their boilers, or the prevention of Smoke in Furnaces, so as to comply with the requisitions of the Act of Parliament, will ensure the realization of the utmost measure of success yet attained, and the latest steps of ascertained practical improvement without encountering the risks incident to the various charlatan projects presented for public acceptation. Mr. Armstrong's fees are very moderate, and any work entrusted to him is executed with despatch. * # * Preparing for publication THE MODERN PRACTICE OF FURNACE ARCHITECTURE, Comprehending CHIMNEY SHAFTS for Steam Engines and FIREPLACES for Dwelling-houses. 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. : ; ffiLJ ~ WS/ACfCS 1 A f I * JAfJ 3 195 7 D JAN 5 tgt J7 NOV 5 1981 * C "0~ *TD OCT^^' LD 21-100m-6,'56 (B9311slO)476 General Library University of California Berkeley u c BER s