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THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[December, 



at Otis moment constructing engines from accurate drawings of those 

 of tliP Great Western. The engines of one maker are frequently put 

 into tlie hands of -.mother lor repair; driinglitsmfn nnd mechanics 

 migrate from one fictory to another, carrying with them all itn mys- 

 teries, and every one knows tliat imy particulars of any practice may 

 he obt.iiiied without considerable trouble. Yet in the face of all this, 

 each engineer imagines that he possesses certain miglily secrets 

 which are hid from all the world beside, believes that the publication 

 of a few very well known expedients would ruin him entirely, and 

 mistakes the rejection by other engineers of the plans he has chosen 

 to adopt, for a happy ignorance of their existence. Opinions, how- 

 ever, such as these, are only to be laughed at, but a dilferent de- 

 meanour is due to those who not only refuse to give any practical 

 information on the subject of the steam engine themselves, hut throw 

 every impediment m the way of those who are disposed to be more 

 communicative. The appearance of Wr. Farcy's admirable treatise 

 on the steam engine was gall and wormwood to these high-minded 

 gentry, because, indeed, " they feared it would make every body else 

 as wise as themselves," and the publication of some of the dimensions 

 of marine engines in a late number of this Journal raised a din and 

 consternation which we could not have conceived possible from a 

 cause so inadequate. For this and other aids to engineering we have 

 been held up as enemies to engineers, and have been charged with the 

 infliction of injury upon individual practitioners, by opening the door 

 to the crowd of uninitiated. But upon what authority was the door 

 ever closed, or when did it become insupportable injustice to hinder 

 men from being unjust to their neighbours? There is but little of the 

 knowledge which contemporaneous engineers possess, which they 

 have not derived from their immediate predecessors, and in attempt- 

 ing to exclude the rising generation from the benefit of this common 

 stock, they have arrogated to themselves a right they never could 

 have possessed. Toleration for their personal prejudices and private 

 aberrations we are n illing to accord in the largest measure ; but who 

 ever heard of toleration for intolerance ? Who ever heard a man cry 

 out because he might not insult and tantalize his fellow creature, 

 choke up his path with thorns, and shut him cut from benefits to 

 which he is equally entitled ? Every one but the members of this 

 parly can see the folly and injustice of such courses, and those who 

 have the interests of those persons most at heart, will be the most 

 solicitous to wean them from them. 



The first article of the letterpress which accompanies the plates is 

 an account of the hulls of the Tnnt and his, which contains some 

 acceptable information. The next article is a short account of the 

 Orion steamer, and then follows a description of the engines of the 

 /«»«, which betrays, we fear, a little superficiality, yet contains much 

 strong sense, and only a moderate infusion of error. After this comes 

 the specification of tiie hull of the Cyclops, and lastly an account of 

 the engines of the Z)i£ and .S'w/way. The few remarks we intend to 

 indulge in we shall drvote principally to the machinery of tlie Trent 

 and /«(«, by Messrs. Miller & Ravenhill, and that of the Dee and 6'o/- 

 nay, by Messrs. Scott & Sinclair, of Gieenock. 



The most conspicuous peculiarity of the engines of the Trent and 

 /8IS is the absence of all pretention to architectural beauty. The 

 frames of the Dee and Solway are of the Gothic order, the crank 

 shaft being supported by Gothic columns. In the Trent and Ists on 

 the contrary, the crank shaft is sustained by unadorned plates of 

 metal, «itli large feathers cast on their sides to stiffen them laterally, 

 so that the section of each support somewhat resembles the figure of 

 a double cross. The purpose of this practice is to distribute the 

 metal properly in every part of the frame. In the case of columns, 

 it is contended, the core may tioat in the process of casting, and make 

 the column thicker on the one side than on the other — a defect to 

 which the crucial system is not liable, but the existence of sucli a 

 defect at all, involves the supposition of excessive negligence on the 

 part of the moulder, and is altogether so remote and unusual as to be 

 only susceptible of measurement by an infinitesimal mensuration. If 

 pipes can be cast without any injurious inequality when the thickness 

 does not exceed half an inch altogether, it is dilhcult to see how the 

 injury can be very serious when the thickness is increased to o or 4 

 inches, and the proportion of any inequality diminished correspond- 

 ingly. 



The author of the description of these engines ascribes great im- 

 portance to the horizontal crosses introduced in the Trent and I»is 

 between the crank and intvrniediate frames of each engine, but we 

 dissent from his judgment in this particular, and attach lar more im- 

 portance to a horizontal cross between the engines. He wastes much 

 rhetoric in showing that the shock of the paddles and the racking 

 which ensues when the engine is reversed constitute strains «liich it 

 is hard tor the framing to resist. But the formidable character of 

 these straius is as regards the framing jiurely imaginary, and the 



whole of this part of the description, though indicating coHsiderable 

 talents, is overcharged, hvpothetical, and pre()03terous. 



The diameter of the cylinder of the Ism is 74i in., the length of 

 the stroke 7 ft., and the number of strokes per minute 1 li ; the mean 

 vacuum in the cylinder 12-705lb. ; the mean steam pressure 2-2351b., 

 which deducting 1-25 for friction, leaves the etfective pressure on the 

 piston 13-l'i9 lb. per square inch. The indicator diagram shows the 

 steam to be cut off at between two-thirds and-three fourths of the 

 stroke. The quantity of lap proper to this degree of expansion may 

 he computed bv a formula we gave in a former number. 



The Isis was, we understand, a very heavy vessel, sank deep in the 

 water, and was in consequence never very rapid. The author of the 

 descrifition before us, suggests, that inasmuch as there would appear 

 to be an objection against working large engines at a high speed, it 

 might he expedient to employ small engines in steam vessels, and 

 work them at such a speed as to produce a power equal tu that of the 

 larger engines working slowly. But there is nothing to prevent large 

 engines from being worked at a liigh speed so far as the engines 

 themselves are concerned; and the speed of the engines of the Isis 

 might easily have been doubled without difficulty or detriment. But 

 if the engines of a steam vessel be worked at such a speed as to in- 

 volve the rotation of the padde wheel with undue rapidity, a large 

 proportion of the engine power will be wasted in throwing the water 

 back from the wheel instead of being spent in forcing forward the 

 vessel. In short, a certain relation must always subsist between the 

 velocity of the wheels' rotation, and that of the vessel's progress; 

 and this must of course fix the velocity of piston which in a vessel of 

 ordinary constrncfiun will produce a maximum effect. Small engines 

 driven "at a high velocity might answer very well if the paddles were 

 on the second motion, a's it is technically phrased ; in other words, if 

 they were so arranged that the engines might run at a high velocity 

 without affecting the relative speeds of the paddles and ship ; but 

 with the present modes of arrangement, small engines would not 

 answer at all : and we do not see how it is possible to apply them 

 under any sort of arrangement, without resorting to cogwheels, which 

 in steam vessels are, it is agreed, objectionable. 



We have never been any great admirers of the engines of Messrs. 

 Scott and Sinclair, yet in many points we admire the engines of the 

 Dee and Solway. They are greatly superior to anything we have 

 hitherto seen from the same factory, and are we think a favourable 

 specimen of engines of Clyde manufacture. There remains, it is 

 true, even yet a good deal too much of the old leaven; the joints, for 

 example, are still made of rust, instead of being metal to rnetal, as in 

 the London engines; the air pump rods are cased, and the iron is ex- 

 posed to the corrosion of the salt water at the lower ends, instead of 

 which they ought to be of solid copper or Muntz's metal; the valve 

 casings are without expansion joints, the effect of vihich must be to 

 keep the joints on the level of the cylinder cover in a state of eternal 

 leakage ; the piston packing consists of three tiers of rings, and is of 

 an antique and complicated description, long exploded in civilized 

 communities; the upper and under portions of the D valves are con- 

 nected bv two rods instead of three, and the holding down bolts are of 

 the most perishable description; yet in spite of these defects, the 

 engines are upon the whole of" excellent quality, and contain, 

 perhaps, more excellences and fewer imperfections than are to be 

 found in the works of some makers of more exalted pretentions. 

 '1 he framing, we look upon as being the handsomest, and among the 

 best of any hitheito constructed ; the side levers and many of the 

 other working parts are well proportioned, and there is luanit'estly no 

 niggardliness either in workmanship or materials. Whatever faults 

 may still adhere to machintry of this firm, they are not, we conceive, 

 attributable to penury of skill, or insensibility to excellence, but arise, 

 we think, from the d'ifticulty of changing completely and suddenly a 

 vicious system. Most of the grosser vices have already been exter- 

 pated, and the whole may be got rid of in a few years time, even at 

 the same rate of progression. 



We have, we fear, drawn out these remarks to a greater length tlian 

 our readers will thank us for, and have only room to observe in reference 

 to the drawings of hulls of vessels here given, that they are excellent. 

 This part of the work contains a large fund of valuable infL'rination, 

 and will, we are sure, he appreciated by a wide circle of readers. 

 The whole of the plates are admirably engraved, and the typography 

 which accompanies them is of the very first quality; nothing, in- 

 deed, can surpass the skill and liberality which shine out in the me- 

 chanical de|iartment of all the works issued by this publisher; and 

 the height ol this very excellence makes us the more regret that the 

 intellectual department is so rarely of a correspondent quality. 



