406 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[December, 



c.u"'°'-riefS to influence the result, and that the piston be not made to 

 travel' at an extreme velocity. M. Pambonr's discovery, therefore, 

 contributes nothins; to our knowledge of the subject, unless it be his 

 intention to allege that the power of an engine is to be determined 

 bv euaeine the boiler instead of the cylinder. If this be his aim v/e 

 wiliinglv surrender to him the full credit of the ingenious suggestion. 



We trust the Institution of Civil Engineers will give their early at- 

 tention to this subject, and define what function cf the length and di- 

 nmeter of a cylinder a horse power should be, so that a uniformity of 

 measurement "may be established among engineers, and purchasers 

 may know what tliey are buying. Should this not be done by the In- 

 stitution we shall attempt the task ourselves— giving the proportion 

 of our principal engineers, the rules for finding those proportions, 

 and a new unit of our own. , . , , 



Surcharged sleam.—Tbe question has been frequently raised whe- 

 ther steam to which a high temperature has been imparted without 

 increasing its elasticity is more economical than common steam. The 

 specific heat of steam has been found bv experiment to be 847, that 

 of water being 1, and if this result is to be relied on, there appears to 

 be a saving worth attending to in the use of surcharged steam. Yet 

 it appears questionable to us whether the specific heat of steam is 

 not the same as water, the apparent diversity arising from some error 

 in the experiment, which indeed in researches of such delicacy it is 

 almost impossible to exclude. There are many analogies in favour of 

 the conclusion that the specific heats of bodies are inversely as the 

 atomic weights, and if that doctrine be true, the specific heats of 

 steam and water must be the s.ime. Yet great economy is said to 

 bare been realized by the use of surcharged steam, and upon the 

 whole it seems worth'while to inquire what amount of benefit may be 

 expected from surcharged steam at a given temperature supposing 

 the specific heat of steam be such as has been determined by experi- 

 ment. 



If e denote the density of the steam, then 45 {- — A will denote 



the diminution of temperature when the steam is rarified to unity, or 

 the number of degrees requisite to be added to maintain the tempe- 

 rature unchanged. The latent heat of steam being 1000% the hea^t 

 necessary to raise water from GO" into steam is 1000 + 152 = 1152'', 

 and if the steam after leaving the water at the temperature of 212- 

 be heated to 600°, and at the same time be prevented from expanding, 



C00° 212° = 3S8° = equal the heat requisite to be added if the 



specific heat of steam were the same as that of water. But the 

 soecific heat of steam is •847. 



.-. 1 : -847 : : 38S : 328 



Supposing now the steam be allowed to expand, 



448+600 = 1048/ ^'^^ '■ ^'^^^ • ' ^°^ • ^^®'® °'' "''^ ^^^" 

 or the steam when permitted to expand, will occupy 159 volumes at 

 the original atmospheric pressure. The density of the steam when 



so expanded will be -^ — -629 .*. 45 (^t^^ — "'^29^ =^'^^ 1^^^' 



absorbed by the steam during its p.xpansion from 100 to 159 volumes, 



/ 1 ..„\ / 1 -829-^ -- / 1 



This is the result 



*i2||i]\ — 45 (-598359) = 26-025015 degrees 



for air, the specific heat of which is •2GG9. 



.-. •2669 : -847 : : 26 : 82°. 

 The total quantity of heat therefore requisite to produce 159 volumes 

 of surcharged steam of the atmospheric pressure and temperature, 

 C00° is 1152 + 328 + 82 = 1562°. To raise an equal quantity in 

 the common way would require 1831"68% for 



100 : 1152 : : 159 ; 1831-G8'say 1832. 



1832 — 1562 = 270° and 270 -;- 1862 : 



; — = of the whole lieat ; 

 0.7 



in other words, by surcharging the steam to the temperature of 600° 

 the saving is a little more than a seventh of the whole fuel con- 

 sumed. 



Deck Pinks. — Every steam vessel should have an iron deck plate 

 above the steam chest: the fore and aft bearers of the boiler hatch 

 sh'ould also be of wrought iron. Boiler plate on edge with angle irons 

 at top and bottom answers well. Dog bolts may still be used in the 

 beams extending from the fore and after to the ship's side, and the 

 knees can be placed as usual. 



Sa'lty valve c.Vs?.— The weights should all lie within the chest or 



within the boiler. The practice of raising the valves by palms acting 

 on the lower extremities of the valve spindles, and attaching the 

 weights beneath the valve with a cutter, which admits those weights 

 to he raised without lifting the valve, is, we think, a good practice. 

 The valve can thus be cased without opening it, which is done by re- 

 lieving the valve of its lower weights, the weights above the valve 

 still keeping it down, though with a diminished force. By raising 

 the palms sliU more, the cutter arrives at the end of the slit in the 

 socket, and then the valve is lifted. The safety valves seat should 

 never be driven tight in and rivetted, but attached by means of a 

 weak flange and a few weak bolts, so that the valve seat would be 

 raised out of its place by the pressure of the steam before the boiler 

 would be burst. The waste steam pipe should always be attacned 

 to the safety valve chest by a socket joint. If fixed by a flange it 

 will speedily be cracked at the neck from the rolling of the chimney, 

 when the vessel is in a sea way, the funnel shrouds never being so 

 tight as to prevent a!l motion of the chimney. . , , 



-S/irfe wZks.— Messrs. Maudslays make all their shde valves up to 

 50 H.P., of the long D description, above that power, short D. Iheir 

 long D's are iust the same as those in common use, but the attachment 

 to the valve rod is at the top instead of at the bottom as is usual. 

 The covers of the valve casings are made so that they may be moved 

 in as the valve faces wear, the bolt holes being oblong, and the part 

 where the joint is faced in the lathe. The joint is made with a piece 

 of sheet lead nol wrapped with canvass. The valve rods are steel; 

 the long D's are of iron, the short D's of brass. Messrs. Miller i: Co. 

 also make their short D's of brass. The practice is an excellent one. 



HYDRAULIC PROPULSION ON RAILWAYS. 



Of the many plans to which the fertile ingenuity of the present day 

 has given birth, for the purpose of diminishing the cost and danger of 

 railway locomotion, the most novel in design, and amongst the most 

 recently invented, is the Hydraulic Railway, for which Mr. Shuttle- 

 worth, of Manchester, has taken out a patent. The principle of the 

 invention was announced 12 months ago, but the patentee has since 

 made considerable alterations in his original plans for carrying Ins 

 design into execution. For the purpose of making it more generally 

 known, he has just published a pamphlet setting forth the claims of 

 his invention, describing at great length its proposed mode of opera- 

 tion, and calculating minutely the advantages to be derived from the 

 adoption of this system of propulsion on railways. Independently ot 

 the ingenuity of the invention, which claims notice on that account 

 alone, the consideration of the subject gives rise to some interesting 

 questions relative to the motions of fluids, that well deserve attention. 

 We propose, therefore, shortly to describe Mr. bhuttlewortli s in- 

 vention; to state the principal grounds and calculations on which he 

 rests its claims for adoption; and by an examination of the phenomena 

 and laws of hydrodynamics bearing on the subject, to ascertain whe- 

 ther this mode of propulsion can be rendered practically available. 



The arrangements proposed by Mr. Shuttleworth for carrying his 

 plan into operation, are in their general features similar to those of 

 the atmospheric railway. A pipe a foot in diameter, with a longi- 

 tudinal slit on the top, is to be fixed between the rails. Within this 

 pipe a piston is to work, which is to receive the propelling impulse, 

 and communicate it to the carriages by means of a connecting rod 

 passing through the opening at the top of the pipe; which slit is to 

 be kept closed by a continuous valve. So far the two plans exac ly 

 agree, and in Mr. Shuttleworth's first proposed mode of working the 

 hydraulic railway, its resemblance to the atmospheric was still further 

 continued. His intention was then to employ an exhausting pump, 

 worked by a stationary engine, the pipes being filled with water. 

 The advantage proposed to be gained by employing water instead ot 

 air in the pipes was the greater facility by which a vacuum could be 

 obtained by exhausting an inelastic fluid. At that period Mr. Shuttle- 

 worth did not seem to have made suflicient allowance for the friction 

 of the water in the pipes, nor for the weight of water the stationary 

 engine would have had to drag along with great velocity. The resis- 

 tance presented by these causes of retardation would, however, have 

 required far more power to overcome than the weight and friction of 

 a rope, the disadvantage of which it was a principal object ol the 

 invention to obviate. It is true, that Mr. Shuttleworth from the first 

 development of his plan contemplated the occasional application ot 

 the direct pressure of a column of water, as an additional means ot 

 propulsion; but he seemed to rely principally on the povver to be 

 gained by the pressure of the atmosphere on the water forced through 

 the horizontal pipes, to supply the place of the water pumped Jrom 

 that portion of the pipe in advance of the piston. 



