I.-,4 



TITE CIVIL i:\mNKKR WD A lU'IHTErTS JOURNAL. 



[M 



tills I shall l)c alile to show is not iienrly so great as inav at first be 

 sii|i[nisi'il. 



It \sill scaiXL'ly Ijo ilispuli-il that the same fliieKiiess ol' plate in 

 cyliiKlei's G feet diainoter, the size of the exterior eyliniler of the Cor- 

 nisli boiler, will bear a water |)ressure at least 3 liines greater than if 

 arranged in the- usual form of a steam boat boiler ; or that the former 

 of T)- Kith thickness W(jnlJ bear «ithont flinehing a proof pressnre of 

 (■>n or 7l) lbs. to the si|nare inch, while the latter would give evident 

 signs of weakness at 20, allhough ever so well stayed. If then it be 

 considered perfectly safe to work steam of ii or 7 lbs. pressure in a 

 boiler w Inch w onld give evident signs of weakness mider a pressnre of 

 20 lbs., surely it is equally safe to work steam of oU or 3.j lbs. in a 

 cylinder of G feet diameter, and i inch thick, which would bear with- 

 out the slightest signs of weakness ISUllis. on the square inch, boilers 

 of this size and thickness being usually worked to 10, l.'i, and even 50 

 lbs. per square inch Then 1 feet diameter, and 7-lt)tbs lhi( kness 

 will be ample for the internal cylinder, and to make security doublv 

 secure, let a strong angle iron be rivetled round the internal cvlindcr at 

 distances of about i feet apart, this would keep the cvlindcr or arch 

 perfect, and so prevent tlie possibility of a collapse, w'itli but trifling 

 addition to the weight of the boilers. 



Now taking equal extent of common and Cornish boilers, the former 

 taking all stays, ice. into account, will barely average S-Stlis in thick- 

 ness, while tile latter wilh its internal tube of IS inch diameter, and 

 .5-lt;tlis thickness, would average about i inch. Tliis makes their 

 respactive weights at 3 to 4, but in order to the successful application 

 cf slow combustion we require addition flue surface, so take 3 to 5 as 

 the ratio of the weight of common and Cornish engines and water for 

 the same [lower, the extra space required for the boilers being much 

 more than compensated, by the small space occupied by the vibratiiin- 

 engine. " 



But to go more minutely into the matter, the weight of a Cornish 

 boiler and water of the size and thickness named, and 35 feet in length, 

 is — 24 tons, exposing a surface '.t3s feet : eight such boilers might be 

 easily set in the space allowed for the Queen's boilers, now 8 X 24 — 

 192 tons, as the weight of tfie boilers, ami allowing 50 tons for setting 

 and clothing, we have 192+ 50= 242 tons, total weight of the boilers 

 and setting, &c.; 938 X 8= 7504 -f- 500 = 15 feet surface per horse 

 power, being one-half more than theusual allowance without increas- 

 ing the weight of the boiler at all, or occupying more space in the 

 vessel. 



But allowing that we have increased the weight of the boilers in 

 tlie ratio of 3-5, let us take the British Queen as the subject of com- 

 parison. 



The total weight of her engines and boilers is 500 tons, and of this 

 220 may go in round numbers for boilers and water, and 3 • 5 • ■ 

 220 : 361., and 500 — 220 + 3(;0 gives G(3 1 -and less 64 ton's being 

 the decreased weight of the vibrating engine = 600 tons, as the 

 weight of her engines and water on the Cornish plan. 



'I4ie account would then stand thus, on the present plan. 



Engines and boilers 500 tons 



20 days fuel 7^0 



Total - - 1250 

 On the Cornish plan. 



Engines and boilers (JOO 



20 days fuel 375 



Total - - 975 



Showing a capacity for 285 tons more cargo, and a saving of 375 tons 

 of poal. 



Though some may consider these figures as exaggerated without 

 being able to assign any reason to themselves or others, save that the 

 plan is im]iossible. those who have examined the subject w ill as- 

 suredly blame me for not having gone far enough : and theie is another 

 class of well meaning men among engineers and others, who have im- 

 bibed such a reverence for the name of Watt, that they almost con- 

 sider any deviation from the plans he followed, or improvements upon 

 the state in which he left the steam engine, to be an insult to his 

 memory, and a deduction from his fair fame; but my admiration of 

 Watt is as great as any man's can be ; I am proud of lii"m as a country- 

 man, and luinour him as a great man, and so liave endeavoured to add 

 a stone to the nioiiument he has raised, bv carrving out a principle 

 whiidi in his lliird ]iatent of 1782, he distinctly propounded, and of the 

 advantage of which that great man seems to have been fullv aware, 

 though be lived not to see it carried into eHect. 



If then i am born out in these slatenieuls, and to disprove the main 

 point, the great increase of duty by expansive working is altogether 

 impossible ; and the others I think ] have succeeded in making toler- 



ably clear, though on some points as the weight of the present boilers 

 and Water (d'the P.ritisll Quc'eii, 1 may have made some slight mislake, 

 iiol .uiKJunting to a few Ions either way, having assimied it from com- 

 parison with others, and not slated it from actual knowledge, vet on 

 the other hand 1 have underrated the saVing of fuel, and allowed ipiiti^ 

 enough fur the increased weight of the boilers, as there Is le^s due to 

 the great extent of surface than is suppo-.ed, the expansion being the 

 point where the power is gained ; and however the ))roposition of 

 adopting steam of increased density may be cavilled at, to the princi- 

 ple of expansive working and slow combustion we must come at last, 

 and by adopting them to their full extent, which I think I have ?liown 

 to be equally safe and perfectly practical. The Cape of Good Hojie 

 is as much within our reach as New York now is, and a speedy and 

 sure passage open to our Indian and Australian empires. 



Such then being the ease, are we content to allow our preconceived 

 ideas to supersede our better judgment, and go on loading our vessels 

 with unnecessaiy coal, and thus uselessly consuming our most valuable 

 mineral — limit at the same time the range of our steam navigation, 

 and the civilization of the world at large; or do our engineers mean 

 to allow that they cannot make a boiler safe under a pressure of 33 

 lb., or that one of the thickness and diameter that I have proposed 

 would not be perfectly safe under that pressuie. If they allow neither 

 of these propositions, then the sooner the subject is seriously taken up 

 the better, as every boat now fitting with the usual beam or side lever 

 engines, (and many of the spbudid m ill packets are being thus fitted), 

 is incapable of being afterwards altered, so as to work expansively, as 

 tliough the boilers may be altered, the beams, &c. would never stand 

 the increased pressure. 



Before concluding, iierhaps I may be allowe<l to correct an omissiori 

 in my last pajier. It is a favourite remark of naval men, " get as ex- 

 tended a hold of the vessel as possible." Now it has often struck me, 

 not only in those vessels I have myself been engaged in, but in every 

 one I have bad the opportunity of seeing, that this very reasonable 

 remark is not only not complied with, l)ut that the power is positively 

 brought to bear on the w nmg place. Thus no attem|>t that I have seen 

 has been made to lay hold of the vessel fore and aft in a line w-l(h the 

 centre of the paddle shaft, but the framing is stayed sideways, or at 

 best slightly supported by the most contiguous deck beams, and the 

 horizontal strain of the propelling power acting at the bearings of the 

 shaft, the engine frame is thus used as a lever to wrench the under 

 frame of the vessel as it were asunder, and an action is thus created 

 tending materially to weaken the vessel and increase the unpleasant 

 vibration, to remedy this defect, and at the same time to prevent the 

 framing and joints of the engine from breaking, uncommonly heavy 

 bed plates have been resorted to; those on board the British Queen 

 amounting at least to 23 tons; now without entering into a discussion 

 on the ])oint, what I propose is this, let a strong flat bar of wrought 

 iron be carried fore and aft opiiosite each engine, gradually tapering 

 away, and running in towards either side of the vessel, being at the 

 same time securely bulled through tenor twelve of the deck beams, 

 on the end of this next the engine, let there be a strong joint and a 

 similar one on the engine frame joined by u strong connecting rod, this 

 would allow suflicient play, and at the same time, if I may use the ex- 

 pression, give the porter a holil of his load by the right place. 



To conclude, if it be considered that I have not gone sufficiently into 

 detail completely to prove every point I iiave advanced, my answer is, 

 I have con9i<ler,ibly underrated the gain, and overrated the loss, thus 

 rendering minute calculation of strength and weight uncalled for; be- 

 sides such would liave been of no value to any one not intimately 

 acquainted with the subject, and practical men can examine it for them- 

 selves. 



My object has been to keep the main jioints of the argument in 

 view, and to make it intelligible to all classes of your readers, and in 

 this I hope I have succeeded, and should you or any of your readers 

 be able to fninish me with the exact weight of the boilers* of the Bri- 

 tish Queen, and the space they occupy, with any further particulars, 

 I will in a future number enter more minutely into the subject, and 

 illustrate by a few sketches my ideas of bow the boilers on the Cor- 

 nish plan should be set and clothed, and wdicre the extent of surface I 

 have spoken of is obtained ; having no doubt that I shall be able to 

 establish every point that I have advanced, bearing on the increased 

 safety and economy of the jilaii proposed, anil at no distant period see 

 it carried into successful operation on a scale commensurate with the 

 inqiortance of the undertaking, and the vital iiiHuence wdiich such an 

 improvement would have on our political and commercial relation with 

 all parts of the world. 



Pimtico, Jlpril 4, 1840, A. S. 



* The niodilication of Cornish boilers I propiiBe lo adopt has no external 

 Huns. 



