1840.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



159 



being also found to be dissatisfactory, she has been repeatedly 

 oft'ered for sale, without success, at less than half price, and may now 

 he found in the East India Docks with a broom at her masthead. 

 Both Maudslay and Seawards refused to construct engines on this 

 principle, and Mr. A. Jlornay has written a paper to show that the 

 trunk engines are good for nothing at all. Mr. Brunei, in defending 

 the character of the Dartford, very gravely assured the Bristolians 

 that she had beaten the "City of Glasgow" l)y two hours in going to 

 Furtsmoutli, a fact, which, if true, it is very fortunate for him that lie 

 did not state in London, for here the City of (jiasgow is a byeword for 

 slowness, a kind of Regulator, by which all the other steamers go. 

 Having said thus much, we shall now proceed to show, by a few cal- 

 cuhdions, the justness of our remarks. 



The engines are to have cylinders of 10 feet diameter and 10 feet 

 stroke, and thus, according to the usual computation of 7 lbs. eft'ective 

 pressure on the square inch of the pistons, assuming their speed to be 

 240 feet per minute, would be equivalent to I151v") horses power, if 

 of the ordinary construction; but as they are to be made with (he 

 trunk, half the transverse section of the latter must be deducted from 

 the area of the piston, (say one-tiiieenth of the area of the piston), by 

 whiidi the nominal power of the engines is reduced to 107.5 horses 

 power. Tliey are expected to weigh, without the boilers, one third 

 less than common engines; we maj' then fairly assiune that they will 

 weigh, with the water in the boilers, SUO tons. 



It is difficult to imagine the motive which has induced the Directors 

 to cram this fiwrinous power into their intended vessel, the pro- 

 poition of power to tonnage being about what is allowed to small 

 boats ; for by so doing they forego the chief advantage which large 

 steamers possess over small ones for long voyages. The natural con- 

 sequence is that the vessel will be able to carry little or nothing be- 

 sides the requisite fuel for the voyage across the Atlantic. 



The whole area of one of the pistons is 7s-.'>4 square feet, from which 

 if we deduct one fifteenth for the half area of the trunk, we shall have 

 for the mean area acted upon by the steam, 73'3 square feet. The 

 mean capacity of one of the cylinders is, therefore, 733 cubic feet. If 

 we suppose the diameter of the paddle wheels to be 30 feet, the vessel 

 cannot be expected to advance more than S3 feet inches for each re- 

 volution, which with 12 revolutions per minute, would give a speed of 

 nearly 10 knots an hour, and the voyage from Bristol to New York 

 would require the vyheels to make about "220,000 revolutions. For 

 this 8SO,000 cylinders full of steam will be used, but as under favour- 

 able circumstances the steam is to be used expansively, we will suppose 

 it, on an average, to be cut oft' at half stroke during one half of the 

 voyage, and used at full pressure during the other half. On this hy- 

 pothesis only 6GO,000 cylinders, fuh of full pressure steam, will be 

 expended, exclusive of n aste. This is equivalent to 483,780,000 cubic 

 feet of steam, to which if we add 10 per cent for waste, the total ex- 

 penditure of steam will be j32,ir)S,u00 cubic feet. We understand 

 the steam is not to be used at a higher pressure than 4 or ii lb. above 

 ilie atmosphere; at the former pressure one cubic foot of water is 

 required to generate 135G cubic feet of steam, so that to produce the 

 above quantity of steam 392,447 cubic feet of water must be evaporated. 



Mr. Armstrong in his work on the Boilers of Steam Engines, gives 

 10 lbs. of coal as the quantity requisite to vaporize one cubic foot of 

 water, but as the usual allowance for marine engines is only 9 lbs., we 

 shall adopt this as the basis of our calculations. On this hypothesis 

 the consumption of coal during the voyage will amount to 1.580 tons 

 uearlv (say IGOO tons, to allow for emergencies). At the commence- 

 ment of the voyage the resistance of the water to the vessel's motion 

 will be of course greater than when she is light; and by the consump- 

 tion of some of her fuel, the engines wiU not be able to make their 

 full number of revolutions ; and it cannot be doubted that under these 

 circumstances a greater amouit of fuel will be consumed in the same 

 distance than when going at full speed, so that it will be scarcely safe to 

 take less than IGOO tons on board it Bristol, particularly as the passage 

 out may be reasonably expected to be prolonged by adver.-e winds, 

 whicli do not occasion a reduction in the consumption of fuel propor- 

 tiuimi to the diminution of the vessel's speed ; for it is clear that, to 

 obtain an equal resistance with fewer revolutions of the paddle wheels, 

 the floats must slip more through the water, and consequently the 

 progress of the vessel must be less for each revolution of the wheels 

 than when she has no contrary wind to contend against. Now the 

 quantity of fuel consumed is proportional to the number of strokes of 

 the engines, therefore the consumption in a given distance, although 

 not proportional to the time occupied, will be greater when the speed 

 is reduced by adverse winds than otherwise. 



The directors have announced that the vessels displacement will not 

 exceed her tonnage, or but slightly, and that she will not vary in im- 

 mersion between Bristol and New York more than 2 feet G inches, 

 attempted to be run to several places on the south coast, but this 



Now the weight of the hull, masts, yards, sails and rigging, boats, 

 cabins, fittings, &c. cannot be safely estimated at less than 110 J tons 

 The engines and boilers with water .... §00 

 Fuel 1600 



Making altogether (without any cargo) .... 3500 tons, 

 wdiich is already 10(10 tons more than the measured tonnage of the 

 vessel. Her draught of water will, therefore, be 3 feet 6 inches, or 

 perliaps 4 feet more than it is expected to be. 



On a rough computation we estimate that the vessel's draught of 

 water will vary about J ft. (J in. during the voyage, by reason of the 

 consumption of 1.500 tons of coal : and for (his reason, as well as on 

 account of the immense power of her engines, the paddle wdieels can- 

 not be made less than 3.) feet in diameter, with 32 floats on each, mea- 

 suring 15 feet in length and 4 feet broad. With a less diameter a speed 

 of 10 knots an hour could not be hoped for with 12 revolutions per 

 minute, even in calm weather, and with smaller or fewer floats the 

 engines would probably over-rim their speed, when (he vessel was 

 lightened by the consumption of the chief part of the coal. If, there- 

 fore, with the rioals immersed 4 feet, the wheels make 12 revolutions 

 per minute, and the vessel attains a speed of 10 knots, as assumedl 

 above, the engines will be brought up to about 7 or 7i revolutions at the 

 beginning of the voyage with IGOl) tons of coal on board, which would 

 immerse'the floats i) feet G inches instead of 4 feet, and the speed 

 of the vessel would most probably not exceed 5| to Gl knots. 



As regards the expense of tlie new vessel, as estimated l)y the 

 Directors, we will cdl attention to the fact that the price per cwt. of 

 angle iron, plates, ^c. increases with their weight, and, if the " Rain- 

 bow "cost 60/. ])er ton weight of iron (which is the fac(), it is not 

 unreasonable to assume that the new vessel will cost 8).'. per ton; 

 but taking it at 70/. only, and the weight at only 650 tons, the hull 

 alone will cost - - £45,500 



Adding to this for masts, yards, cabins, stores, &c. - 15,000 



And for the engines at 35/. per horse power - - 3),000 



We find for the cost of the vessel .... i£95,0L;O 



which exceeds her estimated expense by 20,500/., irrespective of all 

 preparations, accessories, buildings, tools, Src. 



The tools are to cost 30,000/., out of which we find by the last re- 

 port that 19,000/. was paid, and out of the cost of (he vessel 6,800/., 

 leaving still to be paid for the vessel ... - £ 88,700 

 for the work shops ... 11,000 



By the same leport there was expended ... 105,500 



Required to pay debts due 11,000 



Making in all £216,200 



The total number of shares taken falls short of 1,900, and assuming 

 them at that number, and that all calls will be paid, the gross capital 

 of (he Company amounts to 190,000/., or 26,200/. less than the inevit- 

 able disbursements before the completion of the new vessel. Besides 

 this (here will be the rent of premises, clerks' salaries, expenses of 

 management, &c. during the term of completion, wdiich cannot be 

 safely estimated at less than two years. 



Having shown the temerity with which the directors have acted, 

 both in regard to the size of their vessel, and the engines by which it 

 is to be worked, and having proved that it is inexpedient and inju- 

 rious, we have next to consider one of the most outrageous propo- 

 sitions that was ever suggested (o a public company, (hat of setting 

 up a factory for making vessels and engines. Without any attempt 

 to ascertain on what terms the vessel and engines might have been 

 constructed by contract, the directors have themselves determined to 

 execute both," and have accordingly already hud out £20,000, being 

 one f fill of their cajiital, in the purchase of leasehold property ! in 

 digging docks 1 and in buying machinery! and as if it were not enough 

 to waste the limited capKal of (he unfortunate shareholders in such 

 speculations for their own uses, but, as if (o add (he climax to their 

 proceedings, they actually propose to organize a regular factory for 

 making vessels and engines for whomsoever will buy them. With a 

 capital totally insutficient for the legitimate objects of the Company, 

 and having unadvisedly engaged in a most hazardous and unwarranted 

 speculation, the directors waste the resources of the shareholders on 

 objects which it will require a long time to make available. As to 

 how they propose to find money for finishing this vessel, which will 

 certainly cost nuich more than their estimates, or for carrying on their 

 extraordinary operations, no one can conceive, unless they are to bring 

 half shares into the market (o divide equally with the original pro- 

 prietors. To aggravate the injury in particular cases, they are lite- 

 rally employing "(he money of Mr. Acraman, the great engineer, in 

 competing with himself. With regard to the legality of their pro- 

 ceedings, it requires very little knowledge of law to be aware that it 



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