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kingdom;" and he asks, (page 190)“ where are the accounts of • lives lost on board his (Fulton's) boats by explosions, during the • ten years they have run; fourteen now running in New York
state?” As “ Fulton never pretented to liave invented the steam • engine he used, or any part of it,” (page 184) but purchased the first engine from Bolton and Watt, and had the others constructed upon the same principle, it is not necessary to confine the answer to the accidents which have happened to the boats in the state of New York, but only to those which are similar in principle.Most of the accidents which the writer is about to state, are perfectly within his own recollection, and the others, he is assured, can be substantiated, if necessary. All of them occurred on board of boats constructed on the Bolton and Watt, or low pressure principle.
Rariton-New York, . 1 1
Nor is it difficult to account for these accidents on board steam boats, although the engines of Bolton and Watt, have worked on land with perfect safety during forty-five years. In the latter case they are rarely worked with a pressure greater than four or five pounds upon the square inch; the labour they have to perform is uniform, nor is there any objection to the making them as ponderous as may be deemed necessary. But when placed in boats, all their circumstances are changed. Those persons who have travelled much by these boats, and are well acquainted with the steam engine, know that it is very common to raise the steam to a pressure of 9 or 10 pounds on the square inch, and sometimes higher, in order to increase the speed of the boat. To this there is a strong temptation, from rivalship, adverse winds, or the necessarily circumscribed power of the machine. The boilers, from their construction, are usually incapable of bearing this high pressure, and, consequently, burst. Will
the writer of the “ Review" inform us how many accidents he has heard of, arising from the steam engine as made by Mr. Evans? There is a much greater number of them in use in the United States than there are steam boats in its waters; and let it be re. collected, that ihese engines are as likely to explode on land, as on board steam boats, as they are worked in both cases with a pressure equally high. We are told (page 190)“ that if an ex.
plosion takes place by overloading a condensing engine, it will
only make a rent in the boiler, and the steam will escape:” Nu. merous rents of this description have taken place in the boilers of Evans' engine, and the steam or water has escaped without injuring any person. The rents which have been made in the boilers of the condensing engines, it appears have not been equally harmless. A much larger rent is likely to be made in the boiler constructed like those of Bolton and Watt, than in the cylindrical boiler of the Columbian engine, because the former changes its form before it bursts, and this evidently offers an unequal resistance, even where the metal is of equal strength. In the cylindrical boiler there is no tendency to this change of form; whenever a rent takes place it must be only in that point where the metal happens to be weakest, and this of course must be a very small one, as it cannot be weakest, over any considerable portion of its surface. As soon as such a rent occurs, the pressure is instantly lessened on every other part, and the whole danger is over. There is not the slightest analogy between the operation of gunpowder, and of steam, with which it has been compar. ed; in the explosion of gunpowder, an immense quanty of elastic fluid, is instantaneously generated, possessing a force which may rend the strongest as well as the weakest part of the contain. ing vessel; in steam, the elasticity is slowly augmented, and when confined in a vessel of considerable tenacity, and unequal strength, as in copper or wrought iron boilers, cannot possibly tear to pieces, but merely rend it in the weakest part. This, it is believed, is a reasonable deduction from theory; and it has been the uni. form experience in the numerous instances in which the cylindrical boilers have burst. We are told (page 190) that it is * manifest at once to every man, whether he be an engineer or not,
that a boiler cannot be so much forced by a pressure of less than
( one thousand, as by a pressure of more than twenty thousand . pounds on a square foot.” This, certainly is manifest, but it is also manifest, that if one boiler is so constructed as to be twentyone times the strength of another, it will bear twenty times the force, with less liability to yield to the pressure. A boiler constructed to bear the pressure of ten pounds on the square inch, is certainly more liable to yield to that force, than one capable of bearing a pressure of from three to seven hundred pounds is to a force of one hundred and fifty, the latter being the usual strength and working pressure of the cylindrical boiler. We are told (page 189) that “it is not merely from the boilers' bursting, that danger arises where a high pressure engine is used; for in the case of the Norwich packet, the steam swept away the boiler itself, and this swept away every thing, and every person that stood in its way at the time of the explosion; and was thrown in a horizontal direction out of the stern of the boat;” and (page 190) we are informed that in a high pressure engine, the steam, “ as in the Norwich packet, may carry away the boiler itself, (when it is too strong to barst;" and again, (page 194) “that
though boilers may be constructed to bear the required pressure, yet the accident on board the Norwich packet, shows that “the boiler itself may be carried away bodily by high steam."Here is certainly a new discovery in mechanical philosophy, one, the application of which would be more worthy a patent, than all its predecessors. Upon this new principle, steam engines may be constructed which will consist of only a boiler, “ too strong to burst” well bolted down, and highly heated; it will be necessary perhaps to steer stern foremost, as it seems this is the direction in which a boiler is “ carried away bodily by high steam.” If this principle has ever been applied in practice, the writer has never heard of it, except in the well-known trick in the whole art
of Legerdemain,” where we are instructed, “ how to make (dumplins jump out of the pot,” by putting a little quicksilver into them before the pot begins to boil; or perhaps in the equally common experiment of standing in a washing-tub, and lifting yourself up by the handles. The fact is, that the boiler on board the Norwich packet was, from its construction, unsafe; a large portion of it was made of cast iron, from its size and thickness in
capable of bearing the pressure of very high steam. Had it been much smaller in its diameter, and the cast iron ends made of a thickness which would have sustained a higher pressure than the wrought iron sides or in other words, had its construction been like that of the Columbian engine, the fatal accident would never have happened: the side would have had a rent made in it, the fire might have been put out, as has frequently occurred with this engine, the fire-man might have been scalded or killed, which, however, it is believed, has never happened; the rent would have operated as a complete safety valve, the pressure upon the boilers would have been thus instantaneously lessened, and no further evil experienced. Before dismissing the subject of danger from explosion, which is certainly the most important of all the controverted points, permit me to add one other remark:-it must be evident that the time of greatest danger is when a boat stops, and the safety valve is not raised. Accident from this cause is more likely to happen in a low, than in a high pressure engine-in the former, a small increase of heat, will cause the pressure to rise from 5 or 6 pounds on the inch, to 14 or 15, an increase only of 9 or 10 pounds, which is more than the boilers are intended to bear: in the latter, suppose them to be working with 150 pounds pressure; this must rise to 300, (the lowest estimate of the strength of Evans' boilers) an increase of 150 pounds to the inch, before there is any danger of explosion. This could not happen by accident, as the fire would burn down before the requisite temperature could be produced. This differ. ence is evinced in the different modes of practice adopted on board the boats in the Delaware. Those with low pressure engines, on arriving at the wharf, immediately raise the valve and suffer the steam to escape, or it is known the boiler would give way. On board the Ætna, working by a high pressure engine, the practice is to close the valve and fire-place, and preserve the steam for future use;* the boiler is thus tested after the passengers have left the boat, as the heat will rise higher than it can whilst the steam is expended in working the engine.
Much more might be said on this part of the subject, but as I fear, Mr. Editor, that you already think I have claimed a full share of your valuable pages, I shall proceed to a short notice of
* Our correspondent must be under a mistake. Ed.
some other points embraced in the “ Review," (page 189) "as to • the permanent expense in fuel,—the writer continues, (page (189)" we believe the advantage on fair experiment will be • found in favour of the condensing engine; which under circum(stances equally favourable will afford more power with the same • expense."-(Page 191) « For this is the true question, what • is the daily expense of fuel.” “ The great expense of an engine is the fuel it consumes.”
“ The condensing engines of Bolton and Watt, in Cornwall, in the first four months of the year 1816, raised about twentyeight and a half millions of pounds of water, one foot height for 6 each bushel of coals consumed."
“ Woolse's improved duuble (high pressure) engines, raised upwards of fifty millions of pounds weight, one foot high for eveory bushel of coal consumed.” Here is certainly a discrepancy which it is difficult to explain: for four months in succession, the high pressure engines produced an effect with the same quantity of fuel, exceeding that of the others as fifty exceeds twenty-eight and a half; yet the writer of the “Review says that, “ as to the per. • manent expense of fuel, we believe the advantage, on fair expe. (riment, will be found in favour of the condensing engine.” As no reason is given for this opinion, and the fact stated invalidates it, we leave it until some evidence is produced, which shall be candidly examined. “ The advocates of condensing engines ask, " that while machines of this description are so much safer in ..comparison than the others—while they are competent to pro. pel a boat against wind and tide nearly six miles an hour, why • run so much risk for so little advantage?" (page 191.) This question is certainly very kind; but until the premises are proved, no answer ought to be expected, and when adınitted, we sball all be advocates of condensing engines, and there will be no respondent. To guard against the evils apprehended from high pressure engines, we are told that it is proposed (page 193) “ 10 prohibit by legislative interference, the navigating of passage boats by means of high pressure engines, as being dangerous, unnecessary, and calculated “to give alarm even when the danger is • slight.” And it is further proposed, that " whenever by a long course of experience in manufactories, the high pressure engine