the heated tubes, and the still greater mischief of burning and destroying the metal. Hence the evil of burning out the tubes is very great. Also his separators hold a considerable weight of water, from which no steam is generated; and they require to be heavy in metal, to render them quite safe and strong. Mr. Hancock has taken the middle course in subdividing the water in his boiler, having all that can be required for safety, and the weight I believe, on the whole, to be less than that of any other boiler which will produce the same power of steam; for, owing to the freedom with which the steam can get away in bubbles from the water, without carrying water with it, the surface of the heated metal is never left without water. Hence a greater effect of boiling is attained from a given surface of metal and body of contained water, and that with a much greater durability of the metal plates, than I think will ever be obtained with small tubes.

Do you think there is a danger of such an explosion as could do injury from the mode in which Mr. Hancock's boilers are constructed? That danger I hold to be very slight; the metal of Mr. Hancock's chambers will burn through in time, the same as that of Mr. Gurney's tubes will do, but not so soon. I think, taking the thickness of metal to be the same in both cases, no injury will be done by such burning through. The flat chambers in Mr. Hancock's boiler are very judiciously combined, and are secured against bursting by causing the pressure which tends to burst each one open, to be counteracted by the corresponding pressure of the neighboring chamber, and the outside chambers are secured by six bolts of prodigious strength, which pass through all the chambers, and unite them all together so firmly that I see no probablity of an explosion. Mr. Gurney's vessels, called separators, are secured by hoops round them, and, being of a small size, may be made very safe. Hence I think the two boilers may be put on a par as to their security; but there is a decided preference in my opinion of Mr. Hancock's form of subdividing the water and steam compartments, which I believe is carried too far in Mr. Gurney's tubes whereby the water, included within the several tubes, cannot make way to allow the bubbles of steam to pass by it. This is owing to the great length and the small bore of the tubes; and they are so isolated one from another, that the water within them is not able to act as a common stock of water, or to keep all the interior surfaces of the metal tubes thoroughly supplied with water: thence, there is a deficient production of steam and an unnecessary destruction of metal.

Are you aware that, in Mr. Hancock's carriage, the waste steam which is discharged from the engines after having performed its office, is thrown into the fireplace, and makes its escape upwards along with the flame, smoke and heated air, and gas, which ascend from the fire to act on the boiler?-That is the way in which he gets rid of the waste steam which the engines discharge, and I understand that he thereby avoids the puffing noise and appearance of steam which is common with high-pressure engines. Mr. Hancock blows the fire with a current of air produced by a revolving fanner, which is turned rapidly round by the engines, and therefore he requires no tall chimney to produce a draft. Mr. Gurney formerly used a singular fanner to blow the fire, and also a chimney of some height; but I understand he has lately laid it aside, and adopted the plan of carrying the waste steam which has passed through the engines into the bottom of the upright chimney, and there discharging that steam through a contracted orifice in a vertical jet, which, by rising upwards with great velocity in the centre of the chimney tube, gives a vast increase to the draft of heated air and smoke in

the chimney tube, without any great height being necessary; and this plan occasions a most active current of fresh air to pass up through the fire, and urge the combustion. This is a most important improvement in locomotive engines, which has been introduced by Mr. Stephenson into his engines on the Liverpool and Manchester railway, and being there combined with an improved boiler, it has been one of the great causes of the brilliant success of that undertaking. I believe the same plan will be indispensable to the complete success of steam carriages; for chimneys cannot be used high enough to obtain a draft, and blowing the fire is a very troublesome affair. I fear Mr. Stephenson's plan would occasion more noise than is allowable on common roads; but that may perhaps be avoided or diminished by some new ex pedient.

Do you think any danger would arise from the waste steam being discharged over a large mass of fire on Mr. Hancock's plan? Not the least danger; all the waste steam which blows off at the safety-valve, and which the engines do not require, is got rid of in the same way; but I expect Mr. Hancock does not help the combustion of the fuel by thus mixing the waste steam with the flame before it acts against the boiler. Mr. Stephenson's improvement, which Mr. Gurney has adopted, is to discharge all the waste steam into the bottom of the upright chimney with a violent vertical jet, in order to accelerate the draft up the chimney. The waste steam, therefore, is mixed with the smoke and gas, after the smoke had ceased to act on the boiler. The waste steam was very commonly discharged into the bottom of the chimney, in Trevethick's high pressure engines, many years ago, order to mix with the smoke ascending in the chimney, and thus get rid of the waste steam; it improved the draft in that way, by rendering the smoke more buoyant, but only in a slight degree; but the waste steam was not discharged through a contracted orifice to give it velocity, nor was it directed upwards as is now done by Mr. Stephenson, and that vertical jet of steam in the centre of the chimney, gives such an intensity of draft through the fire as was never procured before, and, with the further advantage, that the rapidity of draft so produced, increases whenever the engines work faster, and discharge more steam, just in proportion as the demand for fire and steam increases by that working faster.

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Is there any noise occasioned in that way ?-Yes; but the sound is directed upwards by the chimney, and is not much heard in the locomotive engines on the railway when they are in the open air, but when they pass under the bridges, the sound is reverberated down again by the arch, and then it sounds very loud. The noise is no great consequence there, and no particular pains have been taken to avoid it. The metal pipe of the chimney has something of the effect of an organ-pipe or trumpet, but it is probable the sound might be deadened.

Will the burning out of the plates of Mr. Hancock's boiler, that you spoke of, be attended with risk of explosion of the whole boiler, or only of the smaller divisions of the boiler?It will be attended with no violence which could be called an explosion, nor with any danger whatever, but only with the inconvenience of disabling the carriage until the ruptured chamber is replaced by another. The rupture or crack of the metal plate at the burned place, would let out the water and steam very gradually into the fire, and probably extinguish it. All steam boilers burn out in that manner sooner or later. The different chambers of Mr. Hancock's boiler are kept together by six very strong bolts, which pass through them all, and which are

quite protected from the action of the fire; to burst the boiler those bolts must give way altogether, and there is no adequate force to produce any such effect.

Are you acquainted with the construction of the new steam carriage which started this week from Gloucester to Cheltenham?-I am not, further than that is on Mr. Gurney's plan.

Apprehension has been felt that these steam coaches will be found to give great annoyance to travellers passing them on the public roads, from smoke and the peculiar noise from letting off the steam; do you apprehend such results will take place?-I do not anticipate any great annoyance will result to travellers in other carriages. I have passed Mr. Hancock's on the road several times and Mr. Gurney's also, and have travelled in them often; horses take a little notice of them when in motion, but not much, and very soon become accustomed to them. I once met Mr. Hancock going very quick along the New road, and drew up to see him pass; I had no difficulty whatever in making my pony stand, though rather a spirited one. Mr. Hancock did not observe me; and as I wished to go with him, I turned and drove after him, and after a race to overtake him, I had no difficulty in drawing alongside of his steam carriage for a good way in order to speak to him, and get him to stop for me. The emission of hot air was very sensible, when following close alongside of the boiler at the hinder end of the carriage, but I did not observe any puffing of steam.

Do you think that whatever annoyance exists in the present steam coaches may be removed by the improvement of the carriage, and particularly the appearance of the carriage?-Certainly their appearance may be improv ed; they are most unsightly now. The general question of farther improvements in steam coaches depends upon the general mechanical skill and judgment of the mechanicians who turn their attention to the subject, and the peculiar experience they acquire in this particular branch of mechanics, by continually practising and exercising with steam carriages, on roads of all kinds in all weathers, to find out their defects, and how to remedy them; and what is the best mode of management; also, by building new and better carriages as soon as they have learned what will be better than the present ones. But all this must be at a great pecuniary loss, and some further encouragement must be held out in order to induce the more skilful mechanicians to embark in such a pursuit; for, at present, it is by no means an object of attention to our best and most competent engineers, because they know they would only throw away their money and time by undertakiug steam coaches, even if they were to succeed ever so completely. The patentees are a different class of men; they are the inventors, who have first organized and arranged the combination of machinery which is to be used; and according to law, they have acquired a legal property in those peculiar combinations which they have discovered, that has been their encouragement and stimulus to exertion; but the terms of their patent rights will be very likely to expire before their inventions come into use to such an extent as will repay them their previous costs with any profit thereon; and also, with the present defective state of the law on the subject of patents, they will be unusually lucky if they are able to make good their patents at law, in case their rights are contested. The patentees are not experienced mechanicians or engineers, and have had to learn the business of engine-making and of coach-making as they went on; and a great deal of the deficiency of the present steam coaches has arisen from the circumstance, that they have been

made by persons who were not at that time qualified to execute either a common coach or a common steam engine; but they have acquired more skill, now, and we may expect more finished productions from them in future. There is no mechanician, of the class of those who will be ultimately employed to make the engines and machinery of steam coaches when they do come into use (and who alone can give that perfection of design, proportion and execution, which is essential to their coming into use,) who will have any thing to do with them now; not so much from any doubts that they would not be able to succeed in perfecting them, as from a conviction that the expense of attaining success would be greater than would be repaid by any advantage they could afterwards derive from making such machines, in open competition with every other mechanician who chose to copy after their model when perfected; for that perfection of design, proportion, and execution, in which steam coaches are now wanting, though very laborious and expensive of attainment, would not be grounds for exclusive privileges under the existing law of patents. The patents to the first inventors are the only ones which are professed to be recognised by law, though in effect they can scarcely ever be maintained at law. That is a very important point for the consideration of the committee, and one which deserves great attention. As the law of property in inventions now stands, when a new invention is advanced to such a stage that it may be considered to be tolerably perfect as an invention, no further exclusive privilege can be maintained to compensate for the skill, labor and expense, which must be incurred to find out true proportions, dimensions, weights and strength, which are essential to bring it to bear as a practical business. The law professes to give the whole to the first inventor, although he may have only laid the foundation on which another has raised the superstructure; and if, as usually happens, the claim of the first inventor is set aside, from technical informality in his title-deeds, and also when his term expires, the whole superstructure lapses, to the public. For these reasons, those who are the most competent to the task of giving the finishing touches of practical utility to great inventions, are kept back by being aware that they shall not be repaid. Under such circumstances, a defect of judgment would be proved a priori against any one who might commence such an unpromising pursuit, and that want of judgment which could permit a man to overlook the pecuniary considerations, would not be favorable to his success as a mechanician, in giving that precision of form and dimensions, and that practical utility, to an invention which requires an exercise of the cool judgment resulting from experience, rather than of the genius depending upon original thought.

You do not consider the inconveniences of the present steam coaches to be inseparable from the invention? Certainly not; but I do not think that any of the individuals at present engaged in the pursuit are the most competent persons who could be chosen to overcome the remaining difficulties, being inventors, who have almost completed their parts of the task, and not experienced practical engineers, into whose hands the affair of building the next steam coaches ought now to pass, under the general direction and advice of those inventors. If the building of steam coaches is continued in their hands, they will only advance towards perfection of proportion and execution by slow degrees, as the patentees acquire that general skill as engineers and mechanists which is already possessed by professional engineers. You think that the machinery may be improved by better machanists? I have not the least doubt of it; and yet those mechanists are not the proper

men

of genius to have invented what has been hitherto done by the patentees.

Apprehensions have been felt by trustees and surveyors of roads that steam carriages are more injurious to roads than carriages of equal weights drawn by horses; what is your opinion upon that point? I should not apprehend that the present coaches are injurious in a greater degree than other carriages of equal weights; and when steam coaches are really brought to bear, I think they will be much less so than any carriage at present in use taking horses and the carriage they draw against engines and the carriage they impel, at weight for weight. All my observation upon steam carriages has led me to believe that they do no particular harm to the road. I could never perceive any peculiar marks that they left in their tracks, and, an examination of the iron tire on the edges of the wheels of Mr. Hancock's carriage, shows evidently that no slipping takes place on the surface of the road; and that fact is proved to a certainty by other observations on the working of that carriage. It will be a long time before a sufficient number of steam carriages travel over any road to bring their effect on the materials to the test of experience; but, on general principles, I have no hesitation whatever in stating my opinion that they never will answer as long as they do injure the roads any more than the fair wear occasioned by the wheels of other carriages of the same weight; for any injury they might do to the road must be by slipping of their wheels on the road, which would be a waste of the power of their engines, and hitherto they have had no power to spare; or, if their wheels are too narrow, and they cut deep into the road, the power of the engines will be wasted. If they are to be efficiently advanced, the whole power must be fairly exerted in advancing them forwards along the road, without turning their wheels in vain on the road, or cut. ting ruts in the road. I am confident that, if the wheels slip at all on the the roads so as to lose motion, or if they penetrate so as to make ruts, those coaches will not answer, and the defects must be remedied, or the coaches must be given up. I do not mean to affirm whether the present steam coaches which draw other carriages after them do or do not slip on the road, because I have not examined them; but I am of opinion that, for the ultimate successful application of steam power, the carriages must be so constructed that they will do less injury to the roads than carriages drawn by horses; and whenever steam coaches become common, I think the roads will be most materially benefitted by the change.

Supposing the total weight of a stage or mail coach, drawn by four horses at ten miles an hour, to be two tons, and the weight of the four horses to be two tons, what proportion of the wear of a Macadam road would you expect to be occasioned by the wheels of the coach, supposing them to be the usual breadth of stage coach wheels, and what would be the wear by the horses' feet? It is impossible to fix an accurate proportion for such a question as that; but I have no doubt but that, weight for weight, horses' feet do far more injury to a road than the wheels of a carriage, and particularly so at quick speeds, because wheels have a rolling action on the materials of the road, tending to consolidate, and the horses' feet have a scraping and digging action, tending to tear up the materials. One test of the wear by horses' feet will be in the wear of towing paths for canals, and the railway roads where horses are employed. In either of those cases, the number of horses which pass along is so small, that no turnpike roads afford any ex