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bottom of the cylinder was open to the atmosphere; and a stream of 30 lb. steam was blown into the vessel from a very small orifice, and allowed to escape freely into the atmosphere at the open end of the cylinder. After a short time, when the cylinder had become hot, and was maintained just full with expanded steam at the atmospheric pressure, a thermometer inserted a short distance into the open end, showed a constant temperature of 214° to 215° instead of 212°, proving the total quantity of extra heat that is in high pressure steam; and no condensation could be perceived inside the cylinder, no vapor being visible until the steam had escaped from the cylinder into the atmosphere. This experiment was tried on several different occasions, and on one it happened that the boiler was priming slightly; and when a drop of water came over through the steam pipe and dropped upon the bulb of the thermometer, it was observed to fall suddenly to 2120°, and remained at that point until the water was boiled off, when it again rose 2° to 3o above the boiling point as before.

Mr. Stephenson said he did not think that mode of trying the experiment would give a correct result as regarded the present question, as the steam was escaping into the atmosphere instead of being all confined within the cylinder, and the temperature in the cylinder being maintained above the boiling point would prevent any condensation taking place during the expansion of the steam.

Mr. Cowper did not think that in a cylinder thoroughly protected from loss of heat by radiation or conduction, any condensation of the steam would take place during expansion, and that if any condensation occurred, it would be found to be owing to the steam having lost some of its heat, which it could not recover. The result that he obtained by indicator diagrams from a pair of 35-horse power, high pressure, expansive, and condensing engines, which he had constructed some years since, fully bore out this view; the steam was expanded in the cylinder of each engine independently, and the practical expansion curve was obtained very accurately. The whole body of the cylinder was necessarily nearly at a mean temperature between the highest and lowest steam in the cylinder, (the cylinder not having a steam-jacket,) consequently the steam ought to be slightly cooled on entering the cylinder, and towards the end of the stroke, where it was at a lower temperature from expansion, it ought to be slightly warmed by the cylinder;-now the indicator figure showed both these circumstances to have taken place, for the actual curve during the first part of the stroke, after the steam had been cut off, was rather below the true expansion curve; and during the latter part of the stroke, it was rather above; this also showed that the expansion curve required a slight correction for the extra quantity of heat in the high pressure


Mr. Clark remarked that he had found by the indicator diagrams that a great condensation of the steam took place in exposed outside cylinders during the first part of the stroke, from the coldness of the cylinders, and a considerable amount of condensation also was caused even in protected cylinders, where they were not artificially heated by exposure to the hot air in the smoke box, because the temperature of the mass of metal in the cylinder remained about the mean temperature of the steam

whilst expanding in the cylinder, which might be many degrees below the original temperature of the steam on entering from the boiler. This caused the actual pressure of the expanding steain to be below the theoretical pressure during the first half of the stroke, as shown in the indicator diagram, fig. 3; where the theoretical curve of expansion is shown by the dotted line BCD, allowing for the contents of the steam port and the clearance represented by the space AA. But about the middle of the stroke, the two curves coincide at C, as the steam was then at its mean temperature, and agreed with the temperature of the cylinder; and after that point, as the steam continued to expand and lower in temperature, the cylinder remaining nearly constant was hotter than the steam, and returned some of the heat it had robbed from the steam, re-evaporating more and more of the water that had been condensed, and raising the curve of actual pressure above the theoretical curve at the end D, where the exhaust commences. A portion of the lost steam is thus restored to the second half of the stroke, but a serious loss of power still remains; and the consideration of this action that is always going on to a greater or less extent in the cylinders of locomotives, however well they may be protected, except where they are artificially heated, shows what an important source of economy is to be found in carrying out that principle.

Mr. Crampton thought that enough attention had certainly not been paid to the condensation in the cylinders of locomotives at slow speed; he did not think it was of so much importance at high speeds. It was also particularly of importance in steamboat engines, where the question had not received so much attention as it deserved. He remembered an experiment which showed a remarkable effect of condensation; four condensing engines, of equal size, were working coupled together in a boat, with the steam cut off at one-quarter of the stroke and expanded; two of the engines were then disconnected, and the other two engines were worked, cutting off at half-stroke, using, consequently, the same quantity of steam as the four engines did, cutting off at one-quarter of the stroke; but a greater effect was found to be produced by the steam than when it was used in the four cylinders. This increase of effect appeared to be entirely due to the greater amount of condensation that took place in the four cylinders than in the two cylinders. There were no steam jackets, only ordinary clothing on the cylinders, and he thought much improvement was required in this respect in marine engines, and it was a matter well deserving the consideration of engineers. In reply to an inquiry, he said the boilers were working with salt water, but he did not think that would affect the result.

Mr. Peacock suggested, that part of the effect in the experiment mentioned by Mr. Crampton might have been due to the smaller amount of friction in the two cylinders than in the four cylinders, when giving out the same total amount of power.

Mr. Crampton replied, that a greater effect was found to be produced after allowance was made for the friction, by taking indicator diagrams, and the relative consumption of the water.

Mr. Whytehead thought the loss by back pressure would also be less in the case of the two cylinders than with the four.


To the Committee on Publications.

GENTLEMEN :-In looking over the December number of the Practical Mechanics' Journal for the past year, I see published therein the specification of a new Express Locomotive, recently built for and put in operation on the London and North Western Railway. In some remarks appended to the specification, some stress is laid upon certain improvements in the mode of constructing the boilers, alleged to have been made by Mr. McConnell, the designer of the locomotive in question. By referring to the annexed specification of a patent for improvements in steam boilers, granted to me in England more than a year ago, and which I would request you to publish entire, with this letter, it will be seen that the extension of the fire box into the waist of the boiler, upon which the merit of Mr. McConnell's boiler mainly rests, is not new with him. Nor is the idea new with myself, as I am aware that this same thing has been done in this country nearly fifteen years ago. It was also the subject of a patent in England, granted to Stubbs & Grylls, in August, 1846. In both the above cases the plan was abandoned as not useful, and in my opinion failed, from not carrying out the principle far enough. Whilst I was engaged in preparing my specification in England, in the autumn of 1851, and winter of 1852, two locomotive engines were altered under my special direction, by Mr. McConnell, at the workshops of the London and North Western Railway at Wolverton. One of the above engines was put in operation early in 1852, and to my certain knowledge before the new express engines were commenced. Upon the eminent success of these altered engines, the boilers of the new engines were prepared, the latter being identical in principle with the former, although some what changed in form. I have for many years past been satisfied that the use of such long tubes as are now prevalent in the construction of locomotive boilers, has been, and is, an error in principle, and I think the results which are now being brought out in England, prove my opinion correct. I believe fully, that tubes of ten to fifteen feet in length, as now so extensively, and I might say exclusively, used, will be eventually abandoned for those of half the length, or even less.

I remain, gentlemen, yours, very respectfully,

443 Arch Street, Philadelphia, Jan. 17, 1853.


Specification of Improvements in Steam Boilers. By J. HARRISON, Eng.

To all to whom these presents shall come. I, Joseph Harrison, engineer, of the City of Philadelphia, in the United States of North America, but now residing at No. 10 Oxford Square, Hyde Park Gardens, in the County of Middlesex, send greeting: Whereas, Her Most Excellent Majesty, Queen Victoria, by her letters patent, under the great seal of the United Kingdom of Great Britain and Ireland, bearing date at Westminster the eighth day of December, in the fifteenth year of her reign, did, for herself, her heirs and successors, give and grant unto me, the said Joseph Harrison, her especial license, &c., &c.

Marine Boiler.-Chapter the first. Figures No. 1, 2, 3, and 4, sheet VOL. XXV. THIRD SERIES.-No. 2.-FEBRUARY, 1853.


No. 1, show an arrangement of boiler more particularly adapted for Marine Engines. This boiler, in general appearance externally, is not different from boilers now in use, but it will be seen by inspection, that the arrangement of the heating surface varies from the usual mode, these variations having been made with a view to obtain a more efficient kind of fire surface as well as to increase this surface without enlarging the size of the boiler. By reference to figures 1 and 2, it will be seen that the fire box is carried forward from the fire-place some distance into the interior of the boiler, to which it conforms in shape, and is surrounded with a water space, as shown in figure 3, sheet No. 1. The open space in the fire box above the fire is filled at certain intervals with horizontal tubes distributed as shown in figure 1, leading from the water space immediately over the fire doors to the extreme end of the part of fire box extending into the boiler as above described. These tubes have water covering their interior surfaces. After the flame and combustible gases have passed from the fire upward and through the intermediate spaces between the tubes just mentioned, it passes onward through a series of smaller tubes which lead from the external fire box to the smoke chamber c through the water space B. The smoke chamber c has a series of vertical tubes so disposed as to leave the tubes leading from the fire box free for cleaning from the front end of the boiler. The heating surface in the smoke chamber is arranged so that it may be used either for generating steam by surrounding it with water, or the water from the boiler may be shut off by shutting the holes leading from the water space в to the jacket of smoke box if required. In the latter case the smoke chamber is intended to be used for drying or surcharging the steam previous to its entering the cylinders of the engine. For which purpose the steam pipe D, figures 2, 3, and 4, sheet 1, may be arranged so as to bring the steam from the steam chamber E to the top of the smoke chamber, from whence it is brought in contact with the interior heated surfaces of the smoke chamber, and is discharged in its way towards the cylinders at the opening F, figures 2 and 4. Or the opening F, figures 2 and 4, being closed, and the surface of smoke box and interior vertical tubes being filled with water and used for generating steam in like manner with the other parts of the boiler, then the steam pipe D serves as a means of conveying the steam from the top of smoke box to the steam chamber E. After the combustible gases from the fire box have been brought in contact with the interior surface of the smoke chamber and the vertical tubes contained therein, they return again to the back end of the boiler through a series of tubes which lead from the smoke chamber to the chimney G, passing through the entire length of the series of tubes first alluded to in this description, as shown in figure 2, longitudinally, and in section in figure 1. Figure 5, sheet No. 1, shows a mode of making a fire box or boiler stay, which is intended to be used in the boiler just described, as well as in all the other arrangements of boilers hereafter to be mentioned in this specification. In place of the ordinary screw stay for connecting the exterior to the interior parts of the furnace or fire box, it is proposed to make a stay similar to fig. 5, sheet No. 1, which is fully explained at a single view in section. This stay consists of a wrought or cast iron tube, or of any metal of any given diameter and length suit

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