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low pressure ; and whether they ought “ In fact, you yourself would not to be made of cast iron or wrought choose to use a high pressure engine, iron.

from the difficulty which exists, either It is needless to enter minutely in- more or less ?--'That is my opinion.” to the difference between the struc Mr Timothy Brumah, engineer at ture of the high and low pressure en- Pimlico. "Do you think that a high gines ; the description, indeed, could pressure engine, under any guard that hardly be made intelligible without can be applied to it, is a safe engine plates. It is enough to say, that in to use in a steam-boat ?-1 do not the low pressure, called also the con conceive it is a proper engine, or a densing engine, the power of the safe one.” steam can, with no advantage, be Mr Henry Maudeslay, engineer, raised above six pounds upon the Lambeth.--" I never considered high square inch ; it may be raised higher; pressure engines were applicable to but there is no temptation to raise boats, because the purpose of a high it, because no increase in the pro- pressure engine is to save water, and pelling power of the engine would water cannot be wanted on board a vesfollow. In the high pressure, on the sel; the difference between the one contrary, every increase of force which and the other makes no saving either the steam receives, will produce a cor- in the weight or expence, taking it responding effect in the power of the ultimately, particularly when steamengine; it will propel the boat or ma boats are properly contrived. As far chine with the greater velocity. The as my opinion goes as to steam-enconductors of steam-boats have, there- gines and steam-boats, I would not fore, a temptation, when “ bent on go from here to Margate in a high speed,” to increase the power of the pressure boat.” steam beyond what the strength of He is afterwarıls asked, “ Accordthe engine can bear, and consequent- ing to your experience and knowledge, ly to produce an explosion.

would a low pressure engine be safe The steam-boat at Norwich had a in most cases that can occur?-I never high pressure engine. Mr John Tay- knew a low pressure engine unsafe, lor states, that it was proved to the but it appears that high pressure enpressure of 100 on the square inch, gines have been.” but that no more than 40 lbs. was Mr George Dodd, an extensive usually applied. Mr Bramah con- proprietor of steam-boats on the ceives 60 lbs. to have been the usual Thames." Are all the steam-boats pressure ; but both are of opinion, that you now have, or that you have îhat, at the time of the accident, it had, used with condensing engines ? must have been upwards of 100. - They are.

The following are the leading state “ Has any accident happened durments on the comparative merits, be- ing the course of their being used ? ginning with those in favour of the The boilers of two have been injured low pressure:

by the imprudence of the engine Mr Bryan Donkin.--" Is it your workers; but no accident of any deopinion that a boiler could be made scription could or has occurred to the of proper materials, with safety valves, passengers. and under proper guard and direction, “ Did you see the Norwich steamto make high pressure perfectly safe? packet which exploded? I have been - That would depend upon the quan on board her, and perforined a voyage tity of pressure to be used ; a safety with her ; I went down with a view valve might be carried to three hun- of purchasing it; I went down for dred, or to any assignable force. I that purpose twice. think that a high pressure engine may

“ What was your reason for not be made safe to a certain extent, but purchasing it?-Because it was a high where they are left ad libitum, they pressure engine, and liable to the acnever can be perfectly safe.

cident which has since occurred.” “Is it then your opinion, that in Mr Josias Jessop, civil engineer, high pressure engines carried to that Adelphi.-" There can be no doubt extent you mention, that danger that an e:igine of low pressure must would always operate ? --It would not be more secure than one of high presalways operate, but it would be ex- sure; for although they may be both tremely liable to accidents.

easily made secure originally, yet from

the natural wear and tear, both are ter; the effect seemed to be tremenliable to accidents. If an accident dous; there it knocked down the happen to one of a high pressure, its whole building, which was a suconsequences certainly will be more gar-house of five or six stories high, dangerous than that of a low pressure and fragments appeared to be thrown engine.”

in every direction ; the boiler itself The following testimonies go to was shattered into a great number of prove a contrary opinion :

pieces. Alexander Tilloch, editor of the “ If that harl been a wrought iron Philosophical Magazine.--"My opi- boiler, and had burst, it would not nion is, that, attending to what should have produced the same effect ?-I be attended to in every steam-engine, think not.” and employing proper engineers, a Mr William Chapman.-“ Would steam-engine would be perfectly safe, you not always recommend a boiler to whether with high pressure or low be made of wrought metal on board pressure."

steam-boats ?-On board steam-boats Mr Andrew Vivian, miner, Corn. I would recommend them all to be wall.—“What accidents have happen- made either of copper or charcoal iron ed to steam boilers within your own plates, beat under the hammer and not knowledge, working either with low or rolled ; the resistance of cylindric boilhigh pressure stearn ?-I have knowners will be in the inverse ratio of their of no accident with high pressure diameters.” steam and cast-iron boilers ; but I Mr Philip Tuylor.-" The boilers have known an accident happen work. I have generally employed are coning with Boulton and Watt's low pres- structed of malleable iron, commonly sure engine, which was on the 28th known by the name of charcoal iron, of November 1811, in Wheal Abra- rivetted together and secured by strong ham mine; a wrought-iron boiler wrought iron belts. From observing working with low pressure steam ex- the danger arising from the introducploded there, and scalded six men, tion of Hat cast iron ends, I have tera three of whom died in the course of minated the ends of the boilers by a week afterwards. The steam from wrought iron ones, nearly hemisphelow pressure scalds much worse than rical; this mode of construction, as the steam from high pressure." far as my experience goes, combines

Mr Thomas Leun, engineer for more strength and durability than any Cornwall miners.--" You are then other.” well acquainted with steam-engines of Mr Henry Maudesluy.-"What is every various construction ?--Certain your opinion as to the comparative ly I am; I see fifty-seven every safety of cast and wrought metal used month.

in boilers ? --I consider that wrought “Do you conceive that there is any iron is extremely safe, compared to material difference in the respective cast iron. safety of those engines ?-Some of “ Then, at all events, it is your othe engines are certainly safer than pinion, that, in steam-boats, boilers of others.

wrought metal should be used in pre“ Be so good as to state which, and ference to cast ?-No doubt about it. why?-I conceive there is no danger “ Do you think there is any matewhatever in the use of high pressure rial difference between the use of copsteam-engines; and for this reason, per and wrought iron ?--No, exceptthat, in general, for an engine that is ing in the greater degree of corrosion intended to be worked with high to which iron is liable.” steam, the materials are made strong Mr Alexander Galloway.-“ Under er in proportion than the materials all the circumstances of the case, I used for steam of low pressure.” should most decidedly recommend a

I shall now collect the evidence in condensing engine, a condensing enregard to the comparative merits of gine with a wrcught iron boiler ; a cast or of a wrought iron boiler. because, when cast iron becomes suba

Mr John Tuylor." Have you ject to high expansion and contracever seen an explosion of a cast iron tion, the constant repetition of these boiler?-No, I have not. I have effects in a very great degree impairs seen the effects at Wells Street; I the strength of the boiler." was upon the ruins immediately af Mr John Braithwaite." Would


you not recommend on board steam- boiler?-A wrought iron boiler, proboats, wrought metal boilers to be perly constructed.” used in preference to cast ? --Certain Mr Josias Jessop.' I think that ly; I have made some discoveries my- if the boiler were made of malleable self in the boilers I have put up, metal, such as iron and copper, it which makes them perfectly safe.” would be an additional security.

Mr John Hall.-" I make boilers “What is the ground of your preferin cast iron, and I have proved them ence to malleable or wrought metal?by an hydraulic press made for the It does not burst by an explosion, as purpose, and have gone as high as 250 brittle metal does, but tears; it would pounds to an inch, and that I con- probably rend at the joints. sidered enough ; nothing happened.

“ You do not mean then to say, Mr Alexander Tilloch.—“I would that it would be impossible that a prefer cast iron, contrary to the opi- malleable boiier would burst, but that nion of many people, and the reason it is improbable that it would ?-It I would prefer it is the same for would burst, but it would not fly in which it is preferred in making can- pieces; the rent would create a natunon. It is not possible to get thick ral safety valve.” plates of wrought iron perfect through Mr Arthur Woolf, engineer, Cornout, and you trust at last to rivets in wall.-“ Are your boilers in general joining them, but cast iron boilers can made of wrought or cast iron ?-Of cast be made of any strength you please; iron wholly ; I approve of the cast instead of having a boiler that will iron boilers in preference to any mixstand sixty, it may be made to stand ture of metals. six hundred, of either wrought or Do you consider that the cast cast iron. Another reason why I iron boiler, upon the common conwould prefer cast iron is, that the struction, is equally safe with a sheet iron corrodes much quicker, wrought iron one ?--Not upon the and destroys by oxydation, so that a

construction that I have boiler may be safe when first set up, seen ; some I should have doubted and stand its proof, but very soon be- very much ; I have seen some that are come unserviceable, or at least com- rather dangerous ; my patent consists paratively so."

of one composed of a number of tubes. Mr John Steel." Will you give Suppose a cast iron boiler, and a your opinion as to the comparative wrought iron boiler of about the same merits of wrought and cast iron ?- form and capacity, to be exploded by I cannot conceive as to the safety of the force of the internal steam, do the two, that there is any difference you think that the mischief likely to whatever, when the steam is used, as be produced by each of those would it generally is, for high pressure en be equal ; taking any form you please, gines to 40 pounds to the inch. If it and exploding both, which would do was required to make the strongest the most mischief?-I do not think boiler imaginable, I should consider the wrought iron boiler would sepa.cast iron preferable, because there you rate into so many pieces as the cast can get to an unlimited strength of iron boiler. resistance ; wrought iron you can only “ Then do you think that the exhave of a certain thickness.

plosion of the wrought iron boiler is Mr William Brunton.-“What in- attended with as much danger as the jury do you think is likely to arise cast iron boiler ?-In every thing, exfrom the bursting of a high pressure cepting what depends upon the fragboiler, composed of wrought iron ?--I ments of the iron itself; I have no conceive the injury would be more hesitation in saying that cast iron partial, in consequence of the frag boilers are safer than wrought iron ments being larger ; for I do not sup boilers." pose that the wrought iron boiler Mr Andrew Vivian." Do you would be divided into so many parts conceive that there is any differas a cast iron boiler would.

ence in the liability to explode be“ In a steam-boat, what boiler tween the boilers constructed of would you most recommend to be wrought and

of cast

iron ?- 1 used to insure safety to the persons on should conceive that cast iron could board ; a wrought iron or a cast iron be made much stronger than wrought

iron with less difficulty ; I conceive who construct engines for the use of it to be a very difficult thing to make the Cornish miners. When employa wrought iron boiler so strong as we ed for that purpose, there appears to be can have it cast; we have some of a great saving, in point of economy, in our boilers made two inches thick; the use of high pressure engines. and to make a wrought iron boiler Without, however, supposing any bias equally strong as that, would be very from this cause, the two cases are difdifficult to be accomplished by work. ferent, and different rules may apply men.

to them. It would seem, by the tese * Supposing the only object to be timony of those concerned in steamsafety to the lives or limbs of the per- boats, that the low pressure boilers sons who should be surrounding the burst almost as often as the high presengine, would you in that case prefer sure ; but, in bursting, they do no having the boiler of a high pressure injury; the fragments never explode. engine of wrought or of cast iron? The only danger is from the scalding -I would have cast iron, because of the steam ; but this seems never to it can certainly be made stronger have been experienced in boats, prothan wrought iron for the same ex- bably from the covered state of the enpence."

gine; it occurred only in mines or maMr. Thomas Lean.-" Have you nufactories, where the workmen were any choice, in point of safety only, exposed to the steam. It appears to between a boiler constructed of cast follow, therefore, that his Majesty's iron or of wrought iron ?-Were I to subjects may travel in boats using low have a boiler where I wished to have pressure engines, with perfect safety the greatest strength, I would certain- to life and limb. Moreover, these boats ly have it made of cast iron; I have seem, in all common cases, capable of not one doubt that a cast iron boiler sailing with every degree of rapidity can be made much stronger than it is which can be wished for. The steampossible to make a wrought iron one; boats on the Clyde go, I believe, at in fact, the explosions that we have the rate of seven or eight miles an had in Cornwall have all been in hour, which is as rapid sailing as any wrought iron boilers, but I never had one could desire or choose. There one in cast iron boilers, nor have we seems no motive, therefore, for enhad an accident from high pressure countering the hazard of explosion, steam; all the accidents have been which probably can never be entirely from low pressure steam in Corn- prevented in high pressure engines. I wal.”

am not prepared to say, that the LeHaving thus extracted the substance gislature ought absolutely to prohibit of the examination, so far as relates to the use of boats with such engines ; these two leading questions, I shall because I share the feeling of the now beg leave to make a few obser- Committee, that as little restraint as rations.

possible ought to be placed on the naThe Committee report, that the tural course of human industry. I persons examined “

generally agree, only conceive, that, unless in very pethough with some exceptions, that culiar and special cases, the use of high those called high pressure engines pressure engines in boats can serve no may be safely used, with the precauc purpose, and ought to be entirely distion of well constructed boilers, and couraged. The Committee also appear properly adapted safety valves.” Now, to me to be departing from their own I cannot exactly agree with the Com- principle, when they load all steammittee in this general inference. A boats indiscriminately with troublegreat majority, I think fully two- some and expensive regulations, which thirds, are decidedly against the high seem to be necessary or applicable only pressure engines. It is farther to be in the case of those using high presobserved, that tbese persons include sure engines. If the bursting of low almost aú who have bad any observa- pressure engines never produces any tion of, or concern with steam-bouts ; damage, why require, before every while the advocates of high pressure voyage, an examination by an engiare almost all persons connected with neer, whose presence it may be diffithe application of steam to machinery cult and expensive to procure ? tised in manufactures. They are, in- why also demand, that the boiler deed, almost exclusively the persons should be made capable of bearing sir



times the pressure which it is intend- varieties of organized life, or the died to sustain ?

versified appearances of the laws of The Committee also report, that nature, which are there presented. e a great niajority of opinions lean to The facts which I have to notice are boilers of wrought iron or metal, in not, besides, very generally known, preference to cast iron ;” and they and seem, on both these accounts, to therefore recommend as a regulation, be deserving of a place in your useful “ that all boilers belonging to the en- miscellany. gines by which such vessels shall 1. My first observation relates to be worked, should be composed of that species of marine animal which wrought iron or copper.” Generally is known to naturalists by the name speaking, the same persons who re- of Medusa Capillatu. It is a frequent commend low pressure engines, re- inhabitant of most of the shores of commend wrought iron ; and those this island, and may easily be distinwho advise high pressure engines, ad- guished from the other species of the vise cast iron. We do not exactly same animal, by the remarkable transknow why the Committee has adhered parency of its whole mass; and more to the former in the one case, and to particularly by some beautiful spots of the latter in the other. The general bright purple, which are placed near result seems to be, that cast iron boilers the centre of its disk. I ought, permay be made stronger than wrought haps, to remark, for the sake of some iron, and consequently less liable to of your readers, that the class of aniexplode; but when they do explode, mals, of which that alluded to in the they occasion more damage. On these following observation is a species, is grounds, the preference between the commonly known in this country by two appears somewhat of a dubious the name of the sea-hlubber, and is point. But, at all events, as the only remarkable for several striking proobject in the use of wrought iron is to perties, which characterize some of its diminish the injury produced by an species, such as that of occasioning a explosion, I can see no possible motive feeling of irritation in the skin when for compelling the adoption of it in touched, and of being phosphorescent low pressure engines, which never ex in the dark. To a common observer, ploile. The hardship of such a regu- all the varieties of this animal appear Iation would also be very considerable, to be merely masses of a transparent as it would render useless all the low jelly, scarcely worthy of being rankpressure engines at present composed ed among the class of animals, and apof cast iron, and oblige the proprietors parently driven, without the power of to incur the expence of a new machine. directing their course, by the varying

Upon the whole, the result of the direction of the winds or the waves. evidence here collected appears to be, If, however, on a fine day, when the that there is no ground for giving any sea is calm, and when one of the spe-. encouragement to the use of high pres- cies to which I now allude is swimsure engines in steam-boats. But, if ming near the shore, an attentive eye any proprietors choose to set such on be kept upon its movements, within a foot, it is very proper that they should yard or two of the place of the animal, be made liable to the regulations pro- the following very beautiful and aposed by the Committee. To impose, musing appearance will be observed: however, the same regulations upon As the animal moves forward, it is ali steam-boats, appears to be both un- constantly employed in forming its necessary and vexatious.

disk into a greater or less degree of convexity, while at every such change in the form of its mass, a fringe of most beautiful and apparently silky

filaments, all around the circumfeMR EDITOR,

rence of the disk, is protruded into The following observations, though the water, and again withdrawn into unconnected by any other relation the body of the animal, as it resumes than that of having been made in the its ordinary and more flattened appearsame situation, may probably afford ance. These filaments proceed from an amusement to such of your readers the circumference of a circular space, as delight to wander, at this fine sea- which is placed near the centre of the son, by the sea side, and to remark the animal, and may be distinctly secu


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