Eighth Advantage.-Experience shows that wherever circulation is active, no heat can get above the evaporating point, let the heat be ever so strong*. This boiler is so constructed that no part of it is exposed to strong heat, where strong circulation is not at the same time going on; consequently no over-heating can by any means take place. It is a fact, that no extra heat can get into the steam, since no heat is suffered to pass into the boiler above the water, let it get ever so low. Ninth Advantage.—The tubes of the locomotive tubular boilers now in general use, are riveted at each end; and as no provision is made for guarding against expansion and contraction, the wear and tear is enormous. The tubes, however, in this boiler are connected in the middle, and each half is allowed to contract and expand without impediment. Tenth Advantage.-To separate the steam from the water and foreign matter, a small steam-chamber is attached to the top of the furnace-end of the boiler. A pipe somewhat larger than the steam-pipe passes from the top of the boiler to the bottom of this steam-chamber. Directly over this pipe, a dome is fixed, about three quarters the diameter of this chamber; the depth of this dome is rather more than half a sphere, and within two inches of the top of the pipe. From the bottom of the chamber there is also fixed a return-pipe, half the size of the steam-pipe, which leads down to within two inches of the bottom of the boiler. The operation is thus. When the steam rushes into the chamber, it takes with it more or less water and foreign matter (this is what is technically called priming), which strike the concavity of the dome; the dome throws down the water and foreign matter to the bottom of the chamber, while the steam in a pure state passes off through the steam-pipe, and the foul water returns to the bottom of the boiler through the return-pipe. Eleventh Advantage.—The steam is got up much quicker than in any other boiler, in consequence of the great evaporating surface within it, and the diminished quantity of water in the boiler. Twelfth Advantage. The construction of this boiler is extremely 7th measure showed what I had termed the evaporating point, and in a dense cloud of steam, evaporated suddenly in 6 seconds. 8th measure occupied a longer period, viz., 10 9th measure in evaporating, occupied 10th And the 11th measure did not boil. 20 32 The first measure of water, although contained within the iron cup at a white heat, was perceptibly not in contact with the metal, but was repelled to some distance from it in a state of buoyancy, and there moved freely in every direction. So circumstanced, the water evaporated slowly; but when, by the evaporation of successive measures, and the lapse of time, the iron was cooled down to the "evaporating point,' the water then evidently came in contact with the iron, and the augmented rate of evaporation was as 90 to 6, or as 15 to 1, the rate being increased or multiplied fifteen times; or, in other words, a given quantity of water was converted into steam, fifteen times quicker at a moderately low, than at an intensely high, heat. It is a curious fact, that there are now many boilers which have been in constant use for more than fifty years, the cause is, that these boilers are sufficiently large to make all the steam required, without being forced; this is done with a great sacrifice of fuel: but since it became necessary to economize fuel, the boiler has been very much reduced in size and altered in form, exposing many parts to be overheated. It is true, such boilers raise much more steam with the same fuel; and undoubtedly much more is saved in fuel than is lost in wear and tear of the boiler. This is noticed, to show the great advantage of so constructing the boiler that the heat will always be kept down. screw. simple: the bottom plate, after having been perforated with proper-sized holes, female coupling-screws are firmly riveted into it; the lower half of the tubes, which have been reduced one-third in size, about two inches from their ends, is formed into a male screw, to fit the female couplingThis male screw is faced perfectly flat, and the shoulder is made to be screwed firmly in contact with the bottom of the boiler. The upper half is screwed in the same manner. The face of this screw is rounded, so that when it is brought in contact with the flat surface of the lower half, it may be the more certain to make a perfect joint. The upper half is not allowed to touch any part but the flat surface of the lower half of the tube. The plug-nut, which is used for hermetically sealing up the tube, is perforated in the centre with a small hole,-say one-eighth of an inch in diameter, and filled with a fusible metal, which will be driven out before the tube will rend, and which could only take place should the water be allowed to escape from the boiler. The Waggon Boiler is considered the weakest form. It will be seen, however, by the diagram, that this new boiler is altered somewhat in shape; the bottom is perfectly flat instead of concave; the sides are also flat; the top is semicircular. The female coupling-screws undoubtedly materially strengthen the flat bottom. The boiler is to have tie-bolts from the top, the number of which is to be determined by the strength of the steam to be generated in the boiler; they pass down vertically between the tubes, and are screwed into the flat bottom of the boiler. Tie-bolts are to be used also to hold the flat sides of the boiler from bulging out when used for high steam. None of the nuts of the tie-bolts are exposed to the fire, consequently no objections can arise from that source. This boiler may be made much stronger than any other, on account of its diminished size; setting aside the absence of any danger from the second and third cause of explosion, which has been described, the ends of this boiler, which are flat, may be made sufficiently strong by ribs. In fact, this boiler must be pronounced a perfectly safe one, since only the first kind of explosion can take place, which is absolutely harmless; the first kind has also been described. The ease with which this boiler can be repaired is not one of its least recommendations. Duplicates of the tubes may always be at hand, and if any give way, from unsoundness or any other cause, they can be readily replaced, as they are facsimiles of each other. Thirteenth Advantage.-All persons who have been in the habit of using anthracite-coal, know that the intensity of its heat is so great, that if urged to its greatest power, the best fire-brick is readily fused. It is on this account that it is so difficult to be used for raising steam; still, some careful stokers have used it to great advantage. It is, however, done at a great sacrifice of heat,—for slow combustion and thin firing only will answer. To produce the greatest effect, rapid combustion, with a deep fire is necessary. In the new boiler, the heat cannot possibly be too great. This coal, which is called in Wales, stone-coal, may be obtained there in any quantity, and is undoubtedly the most economical where it can be used, as is the case with this boiler. JACOB PERKINS. REVIEW. I. On the Construction of Coaches, by SIR HENRY PARNELL, Bart. M. P. Nov. 1835. Folio, 12 pp., 2pl. Printed for gratuitous Circulation. A JUDICIOUS and well-timed enumeration of the points of desirable reform in the construction, &c. of our stage-coaches, Hitherto the errors and prejudices of coachbuilders and wheelwrights (except the latter in Edinburgh and its neighbourhood,) appear to have been unconquerable. The dished-wheel and the bent axle are still exclusively manufactured in the London workshop and the village shed; and though "the roads are now no longer cut into deep ruts and holes, the coaches are all nearly as heavy as they were fifteen years ago!"-p. 10. The suggestions of the author, for the removal of these and other objectionable practices almost as universal, are detailed with perspicuity, and explained by plates, containing elevations of the side and back, and a transverse section, of an improved coach. The principles which are the basis of the proposed improvement are fully given; but the application of them is advised to be carried no further than experience will justify; and it is demonstrated, that this valuable guide has long shown, that in a perfectly-constructed coach there ought to be The greatest possible height of all the wheels. depression of the body. length of axle-trees. diminution of bearings and tires. That these conditions are not yet fulfilled by our stage-coach builders, and that they may be made "without departing very much from the present plan of building coaches," the author shows by a "comparison of the size of a coach built on the proposed plan, and of a common coach." (p. 10.) Every stage-coach passenger (and who is there now, male or female, that is not, occasionally at least?) will sympathise with the following remark, and the proposed remedy. The convenience of travellers has been very little attended to in arranging the size of the bodies, and the height and depth of the seats inside coaches. The object should be to enable the traveller to sit in such a position as will admit of his performing a long journey with the least fatigue. A slight degree of consideration will make it clear, that the seats should be so high as to give ample room for the legs, and thus allow the whole length of the thighs to press upon the seats, and be supported by them. If the legs have not room to hang perpendicularly, and are therefore thrown forward, the fore part of the thighs are elevated, and the weight of the body is made to rest on the upper part of them, so as to produce a partial strain on the muscles in supporting the body. In addition to this, the body is thrown backwards, and the weight of it is hereby supported with a considerable strain on the muscles of the back which leads to fatiguing them. There can be no doubt that a person who sits on a high, deep, and broad seat, and in an erect posture, as he does naturally on a well-formed high chair, will suffer less fatigue, than one who sits on a low seat, and in a reclining posture. The popular prejudice in favour of the load being as forward as possible, Sir H. P. attacks. He says, According to the established law of mechanics, that the higher the wheel the easier a weight upon it is drawn, when a carriage has two sets of wheels, one of which is necessarily lower than the other, the body of such a carriage should be so constructed, and so placed over the wheels, that the greatest possible portion of the load should be over the hind wheels. And he advises : In order to keep the weight of luggage as far behind as possible, nothing but carpet bags and light packages should be put into the front boot. As the top of the coach will be only seven feet six inches from the ground, portmanteaus and other heavy luggage may be put upon the roof. If three feet three inches of the roof next the guard's seat be used for this purpose, the weight of the luggage on the roof will be over the hind wheels. For still further securing the object of having the weight as far behind as possible, a strong iron should project, one foot from the bottom of the hind boot, having an iron frame, eighteen inches in length, fastened to it with a hinge, so that extra mail bags, and heavy luggage, may be packed to the full height, if necessary, of the top of the guard's seat. In packing coaches, the hind boot should be first packed, and then the hind irons. The fore boot should be used only for parcels and luggage to be dropped or taken up on the road. On two other disputed, but important, points, the Author says, As the practice of dishing wheels, and bending the ends of the axles downwards, originated in some degree in the bad state of the roads, now that they have become so much improved, the bending of the axles should be wholly laid aside*; and the degree of dishing given to the wheels should be reduced, and made wholly to depend upon experience, with reference to the wearing out of wheels, and the expense of renewing them. The above are the principal points insisted upon; and if the alterations they demand in the construction, arrangement, capacity, weight, and loading of stage-coaches, were carried out into practice, the following most valuable results, among others, would be obtained : 1. A diminution of the labour of the horses; and, 2. An increase of the convenience, ease, and safety of the passengers. Though Sir Henry Parnell bears his own testimony to the practicability and necessity of the proposed improvements, (and probably more unexceptionable evidence could not possibly be obtained,) he has thought it right to support his assertions by extracts from scientific writers; but wishing to strike a still heavier blow at the very root of the evil, by clearing away the ignorance of our wrights and builders, through the means of actual trial and experiment, he adds, [A slight inconsistency has escaped the attention of the author on this point; following out sound principle, he here advises the total banishment of the bent axle; but, at p. 5, he recommends, in order to obtain a particular effect, that it shall still be used, though with a reduced droop.-ED.] Although the extracts, which have been taken from works of science, are quite sufficient to convince all persons who have received a scientific education, that the fore wheels of a coach ought to be high, and that the greater part of the load should be placed over the hind ones, as it happens that few of those persons who are concerned in the directing of the building, and in the building of coaches, have ever applied themselves to scientific inquiries, so as to know either why spokes are called levers, and what the property of the lever is, or what the effects are of the friction of wheels in turning on their axles, and in moving on roads, it is quite necessary that experiments should be made, so that by showing how much work horses actually do in drawing different kinds of carriages, nothing shall be left wanting to expose the prevailing errors, with respect to wheels, and the proper manner of loading coaches. The invention, by Mr. M'Neill, of an instrument, for trying the draft of carriages, which has been found to be perfectly fit for the purpose, now admits of such experiments being made, with a certainty of leading to accurate results; and it is very important that they should be made. As this instrument can be fixed to a coach, with the horses to it, what it shows is, the actual force or labour which they exert in drawing; and, therefore, the experiments made with this instrument are not liable to errors, like other experiments, where it is necessary to use a substitute for the real power. The expense of making a proper set of experiments would amount to some hundred pounds; as, however, there exists nothing to make it worth the while of any private person to incur it, these experiments should be ordered and paid for by the Government. This small expenditure would soon be repaid by the saving which would be effected by diminishing the labour of horses in drawing stage coaches, and, consequently, the expense, which now falls indirectly on the public in providing a sufficient number of them, and maintaining them. We are informed that Mr. M'Neill has, at the request of the Prussian Government, lately constructed an improved instrument of this kind, probably the most perfect of any yet made. This request of a distant nation, may enable us to form an opinion of the vigilance and activity of the part of the administration of that country which superintends the maintenance of the public roads and carriages. And shall England be behind in the further examination of a question of such importance to its commercial prosperity? Shall a country, in which so large a part of its population is, day and night, continually on the move, be still unable to state, on undisputed grounds, what is the best form, and weight, and construction of a safe vehicle of transport? It might have been very difficult to have done this even a very few years ago; but now, when so experienced a person as the author of this work states, that we have, at the present moment, all the data and the instruments necessary, and that the solution of the problem merely waits for a moderate pecuniary aid from the State, let us hope that our ignorance will not be permitted to continue much longer. II. Mathematical Researches. Parts I., II., and III. By G. J. JERRARD, A.B., Bristol. London, Longman and Co. UNDER this very wide and unexplanatory title, Mr. Jerrard has given to the world the fruits of a most extensive and profound investigation of the |