« PreviousContinue »
similar substances are in contact, as when a gate of one kind of wood is fastened with pins of another wood, some action tending to loosen the pins prematurely takes place betwixt them.
"On Tubing the Boilers of Locomotive Engines." By George Buck, M. Inst. C. E.
In this communication, the author has attempted to determine the diameter of the tubes of the boiler of a locomotive engine, so that the effect in the generation of steam may be a maximum. The following are the conditions upon which the problem is solved: That the evaporating effect of the hot air, in passing through the tubes, is in proportion to the extent of surface in contact with the hot air, and as the time of contact conjointly. The following are the results of the investigation: The distance between the centres of two adjacent tubes should be equal to four times the interval between their internal surfaces—the diameter of each tube should be equal to three times the same interval-that the tubes should be as near each other as possible.
In illustration, Mr. Buck has drawn two sets of tubes of the locomotive boiler as generally employed, and one as they would be arranged according to the results of this investigation. On comparing the products of the aggregate periphery, and the aggregate area of the tubes, it appears that the boiler tubed according to the above theoretic proportion is from 23 to 26 per cent. superior to the others.
"On the State of the Suspension Bridge at Montrose, after the Hurricane of the 11th of Oct. 1838, with Remarks on the Construction of that and other Suspension Bridges, in reference to the Action of violent Gales." By C. W. Pasley, Col. R. Engineers; Hon. M. Inst. C. E.
By the hurricane of the 11th of Oct. 1838, one-third part of the roadway of the bridge at Montrose, with a very small exception, was carried away. The suspension rods on the west side were either broken or very much bent, but the chains, four in number, and extending in two parallel lines of two tiers each, appeared perfect. The distance between the piers is about 410 feet; and the chains had been strengthened by additional bars, or plates, since the bridge was erected. The statements of Mr. Provis, and the author's own ob
servations, led him to the opinion that the motions which a bridge
Feb. 5, 1839.
The PRESIDENT in the Chair.
The following were ballotted for and elected :-Alfred Burges and John Taylor, as Members; Joseph Baxendale, J. M. Parsons, J. Bennett, as Associates; and Charles Wood, M.P., as an Honorary Member.
At the preceding meeting, Mr. Cottam had mentioned an instance Corrosion of iron inclosed in lead for 90 years, being taken out with the fin Substances
and bloom unimpaired. Dr. Faraday inquired whether this was in London, as the quantity of sulphurous acid in our atmosphere from the coal we burn occasioned corrosions which do not occur in other countries. This was especially remarked by foreigners. Some years ago considerable discussion took place on the more rapid decay of the stone in the front of Somerset House, than of the same stone in other situations; it had not occurred to him to refer it to the acid in the atmosphere.
Mr. Sibley remarked, that Westmoreland slating, which is extremely durable in other places, will not last in London.
Mr. Cooper had often observed the large quantity of sal-ammoniac and muriate of ammonia always to be found in the atmosphere of London. This arose from the soot, the rain washing it out; as might be at once ascertained by collecting some water, during a shower of rain, on a clean glass-muriate of ammonia was always in excess.
Mr. Lowe inquired whether any one had observed in the spouts conveying water from the tops of houses a pellicle as of a volatile oil, or oxidable matter, on the first water from the tops of all houses, after a dry season. This peculiar pellicle is irradiscent, and disappears after a few hours.
Mr. Williams laid before the Institution a series of specimens of turf, from the first state as taken from the bog, to the last when compressed, and after it was converted into a hard coke. He also described the new resin fuel, or artificial coal, and which was composed of resin and turf coke.
This resin fuel has been used in the Transatlantic steam vessel; and, besides its heating powers and the saving of weight, it enables the fireman to maintain the required pressure of steam with great regularity.
The mode of using it was described to be to throw it in front of the furnace, after the charge of fresh coal. The result was, the keeping up the steam until the coals burned up, and a better combustion of the coal took place. As the result of several trials, it was found that 2 cwt. of this fuel was equal to 7 cwt. of Lancashire coal. It was not used alone, but associated with the coal. The vessels to New York took out from 40 to 60 tons each of it. Thus 2 cwt. of the resin fuel and 20 cwt. of coal, was equivalent to 27 cwt. of coal. In practice, the steam vessels now carry and use a large quantity of resin, but which could only be used in connexion
with small coal or cinders. This new fuel was, therefore, more economical than resin. The price was 35s. to 40s. pr t on.
Mr. Lowe remarked, that the statement of Mr. Williams respecting the peat fuel, led practically to inferences contrary to the results stated in Mr. Parkes's paper, and to Mr. Apsley Pellatt, and to his own experiments, viz. that 9 lbs of coke would do as much in any department of the arts as 12 lbs. of coal.
Results so diametrically opposite, and from persons working on the large scale, and of known accuracy, were not to be disputed. It seemed that we had either yet to learn some unknown laws of combustion, or that the experimenter had not been alive to the differences resulting when combustion was conducted under the widely different circumstances which each experimenter might have in view. Mr. Parkes's test was the evaporation of a known weight of water by a known weight of fuel, coke or coal, employed. Mr. Pellatt's test was the circumstances most beneficial to the temperature of a glass-house furnace. Now these results, wonderful to relate, were strictly in accordance with the results of the experiments of Marcus Bull of Philadelphia, whose test was the raising the temperature of a chest of known cubical contents (512 feet), by 10 degrees of Fahrenheit. All these experimenters find that, so far from coal and coke having the same value, it requires 4 lbs. of the former to produce the same effect as 3 lbs. of the latter. Now it does appear that the results of Mr. Williams are conflicting with these. finds that equal work is produced in the marine engine by substituting 1 ton of a mixture of peat and resin for 4 tons of coal, which coal, in its composition, weight for weight, must contain a far less quantity of hydrogen and oxygen than is known to exist in the generality of peats. It appears that 1 ton of peat and of a hydrocarbon, far more inflammable than coal, supersedes all the carbon, hydrogen, oxygen, and a little nitrogen, combined in four tons of coal. I would suggest as a theory for investigation, whether it may not be found that the coal or other fuel, which contains chemically combined the least oxygen, will not in its combustion give off the most available heat, owing to the oxygen combining with the hydrogen producing less water, which, as aqueous vapour, will carry up the chimney a large portion of the heat, but in a latent state.
Mr. Cooper remarked, that Marcus Bull's experiments were hardly applicable to the present inquiry, as he had constructed a box by which to ascertain how much air was heated by a given quantity of fuel, looking more to the domestic economy of the fuel than to its uses in the arts.
Dr. Faraday was of opinion, that a close comparison ought not to
be instituted betwixt the application of heat to glass pots and to a boiler. In the former case an immense quantity of heated air passed away as in the smelting furnace for iron, where a greater weight of air passed through the furnace than all the other materials, as coal, limestone, and iron-stone; in the latter case there is an immense demand for latent heat. We know that a very small quantity of fuel is sufficient to heat and keep hot a large mass of matter where there is no rapid absorption of latent heat.
The experiments just referred to shew little as to the absolute quantity of heat in different fuels, as there was so great a difference in the quantity worked out in the two cases. To imagine that the coke of a chaldron of coals should produce as much heat as the chaldron of coals could not be the case, or the heat of the coke oven would go for nothing. But there is so great a difference in using coke and coal for heating glass pots and under a boiler, that the two cases cannot be compared. He should conceive that very great advantages might. result from having a resin fuel in the front of the fire; the resin would, perhaps, not be advantageous by itself, but more advantageous with an inferior than with a superior coal.
Several instances were mentioned in which it had been attempted to render the heat of coke ovens available for other purposes; the results were very contradictory. Many patents had been taken out for this purpose, but they failed. In one case, a coke oven heated the boiler of a steam engine, but the steam generated was barely sufficient to move the engine when doing no work. It was found, also, in some experiments, that a proper coal for coking being used, there was no available heat for the generation of steam,—an improper coal being used, there was steam, but little coke.
Analysis of Coal.
Mr. Lowe remarked, that the analysis of coal was very imperfect. One author tells us that cannel coal contains no oxygen; but the gas maker knows that this coal, though previously perfectly dried by being brought to a boiling heat, yields three times as much water, called ammoniacal liquor, as any other coal. This results from the combination of the elementary oxygen and hydrogen producing water, which as vapour is extremely greedy of heat. It was an important inquiry, whether the quantity of elementary oxygen in coal may not occasion the difference between it and coke.