ON THE ADVANTAGES of large wHEELS AND BENT AXLES. 439 Finsbury-square, turn round the aircle, and return to Paddington, without stopping, and carrying a weight in the omnibus equal to twelve passengers? 2nd. Can Mr. Gurney's coach do the above distance in one hour? 3rd. What will be his consumption of fuel? 4th. What will be the pressure of his steam? 5th. If he does the journey ONCE, will he repeat it four times in each day for one week? 6th. Did he ever yet go twenty-five minutes without stopping? 7th, and lastly. How many times did he stop in going round Hounslowbarracks, to point out to his Grace the Duke of Wellington the beauties of his machinery? I remain, In Nubibus, Feb. 10, 1830. ON THE ADVANTAGES OF LARGE WHEELS AND BENT AXLES. Sir,-When drawing up the account of wheel-carriages, which appeared in your 325th Number, I made a sketch of the lines described by the centres of wheels of different sizes, on roughly-paved roads; but, considering my description so plain as to render this unnecessary, and being unwilling to occupy too much of your valuable pages, to the exclusion, perhaps, of more interesting matter, the sketch did not accompany that communication. Your correspondent, "BENEVOLO," has, however, thought otherwise, and has at p. 389, supplied what he considers a deficiency. Unfortunately, however, his illustration makes a sorry contrast with my description: 440 EFFECTS OF DIFFERENT WINDS ON THE COLOURS of vaPOURS, better than that supplied by "BeneVOLO." Referring your readers to p. 174, I need only quote part of my former remark, wherein I stated, "that in passing over a rough or unevenlypaved road, (such as yet abound in many parts of the metropolis*) a small wheel sinks into every little hollow, and the axle, if noticed, would be found to describe a line almost as curved and irregular as the surface of the road." The truth of this assertion is satisfactorily established by the line Be in the accompanying sketch, which is the line actually described by the centre of the small wheel B in passing over the roughly-paved road, which is there represented. This wheel may be supposed to be one foot in diameter, such as is frequently used for the fore-wheels.of low chaises. Again, "a large wheel on the same road would be affected but slightly by its inequalities, and the line described by the axle would be found to deviate but little from a straight line." This I consider also incontrovertibly established by the line a, b, which is that described by the centre of the large wheel A (about 74 feet diameter) in passing over the same road as the smaller one. This line is, in regard to the inequalities of the paving, a straight line-curved only where the road deviates from the level. "BENEVOLO" might well observe, looking at his illustration," that the difference between the line formed by the centres of the large and small wheels, is not so great as Mr. B.'s letter would lead one to imagine!" I would now ask, is it not quite as great? But the delineation of the lines described by the centres of wheels in passing over rough roads, is so easy, that I need not farther trespass upon your columns. Permit me to say, I felt great pleasure in perusing the interesting communication of Mr. Murdoch, on the advantages of large wheels, at p. 183; and also Mr. Thingk's (Knight's?) description of the Guernsey cart, in And of which the prefixed is by no means an exaggerated representation. your last Number: which affords a practical proof of the advantages attending the adoption of the BENT AXLE, which I so strongly recommended at p. 204. The ingenious contrivance for loading and unloading, with which your correspondent was so much struck, has for many years been used in London by the Phoenix, Royal Exchange, and London Assurance Fire-Offices, for raising and lowering their engines into and out of the carts in which they are conveyed about town. In these the inclined planes and the windlass are applied exactly as is the Guernsey cart; and I can only wonder, that our cart and waggon-builders have not, ere this, perceived the great advantage and convenience which this simple addition to their present construction would afford. I remain, Sir, Jan. 25, 1830. EFFECTS OF DIFFERENT WINDS ON THE COLOURS OF VAPOURS. Sir, The first article of your miscellaneous column, p. 320 of No. 333, inquires concerning the "effects of different winds on the colours of va pours," rather by a statement, however, than a question. Different winds" no farther effect the "colours" of a hemispheric medium, or floating 66 vapours," than by rendering them more or less dense: all the various effects of colour being entirely produced by the influence of light, and all being explainable by the proved axiom" that the ray of reflection and the ray of incidence always form equal angles from the surface reflected on." And with regard to the various apparent colours of "distant hills," all substantial bodies resign their local appearances, according to the proportion of their distances; and their evidences of unevenness soften through the perspective diminution of the parts into apparent smoothness, and consequent glossiness, until finally, in the extreme distance, a mountain assumes the apparent texture of a cloud both in substance and colour. The degree of glossiness is not solely to be HALL'S PATENT STEAM AND GAS ENGINE. attributed to smoothness and moisture of the snow, as found on the continental mountains, but to that effect of smoothness which is produced by distance, becoming thereby an effectual mirror; and conveying the colour of the sky, or clouds, to the spectator's eye by reflection. The softening or the lowering effects of density of the atmosphere must be considered, according to its degree, along with, and not in opposition to, this radical cause of distant colours. In conformity with the above conclusions, all the variety of colours seen on distant ob 441 442 DANGEROUS EFFECTS OF REMOVAL of the OLD LONDON BRIDGE. the same time be employed in the generation of vapour, and thereby keep up the supply to the engine equal and unremitted." "The figure of the furnace is that of a hollow cylinder; it is made of great strength, and all the joints are very firm and air-tight. The grating upon which the fuel rests is peculiar, being similar in shape to a double hopper: it is supplied with coke, or other fuel, through an aperture dat the top of the furnace; and the dust and ashes are raked out from underneath by a properly-formed iron through the aperture e. Both these apertures, d and e, are furnished with large stop-cocks of sufficient capacity for the reception of the coke, and for the discharge of the ashes and clinkers, as often as may be necessary; and the furnace-cylinder is by this contrivance kept air-tight when the cocks are shut." I think the foregoing extracts are enough to explain the sketch; but it appears that the patentee also lets a portion of steam under the grate by the pipe h, which passes through the ignited fuel, and is partly decomposed; forming altogether a heterogenous, expansive mixture, from which he derives power at the smallest possible expense of fuel. I have been induced to take the trouble of transcribing the above, on the old English principle that a lookeron has a right to see fair play; and the circumstance of the date would give to Mr. Hall the merit of first using the decomposed atmospheric air (or the nitrogen) along with highpressure steam. I shall conclude with a quotation from a keen observer of human nature, where he says,― "Man's a strange animal, and makes strange use Of his own nature and the various arts, And likes particularly to produce Some new experiment to show his parts; This is the age of oddities let loose, Where different talents find their different marts: You'd best begin with truth, and when you've lost your Labour, there's a sure market for imposture. "What opposite discoveries we have seen! (Signs of true genius, and of empty pockets,) One makes new noses, one a guillotine, One breaks your bones, one sets them in their sockets; But vaccination certainly has been A kind of antithesis to Congreve's rockets." As your work appears to be conducted upon the principle of fair play and free discussion, I doubt not but you will insert this; by doing which you will oblige, Yours, &c. Derby, Jan. 5, 1830. J. SYNGLEMAN. DANGEROUS EFFECTS OF THE REMOVAL OF THE OLD LONDON BRIDGE. Now that the New London Bridge advances to its completion, and the Old one is on the point of being removed, the London public is beginning to manifest a degree of anxiety about the effects which these improvements - if such they must, in courtesy, be called-are likely to have on the trade and navigation of the river, which, though sufficiently laudable, is, it must be confessed, somewhat of a posthumous description. "Better late than never," said the man who discovered that he had built a house without a chimney-" 'tis lucky the fires were not lighted." Not much discreeter, we apprehend, has been the conduct of those who have had the sway in this bridge-building affair. 66 Build, build the bridge, and make it high and spacious," seems to have been all the cry: but what the effect might be of substituting a structure which should give a free course to the stream, for one which has served for centuries as a dam to the upper waters, seems never to have been once thought of, or, at least, not to have been deemed worth a serious thought. And now that this reckless course of proceeding is beginning to threaten a thousand awkward consequences, all the consolation the authors of it have to offer us is an echo of the blunderer's remark on forgetting the chimney"We have built a new bridge, to be sure, without caring for the river; but, DANGEROUS EFFECTS OF REMOVAL OF THE OLD LONDON BRIDGE. 443 better late than never; 'tis luckily thought of before the dam was actually removed." We do not mean to say that it is now too late to find a remedy for any injurious effect which the erection of the one bridge and the demolition of the other are calculated to have on the river; we desire merely to hint how much wiser it would have been to ascertain distinctly the probable consequences of both measures before they were resolved upon, and before a million and a half of money was expended upon them. But was there really no previous inquiry? Oh yes, Inquiries and Reports in abundance. But for any regard that was paid to the facts elicited by these Inquiries and Reports, they might as well have never been made. The reason assigned for building a new bridge in the preamble of the Act of Parliament obtained for the purpose is, strange to say, a concern for the very thing which has been, in truth, so much disregarded-the navigation of the river. "Whereas the great fall of water at certain times of the tide, occasioned by the large starlings and piers of the said bridge, renders the navigation through the said bridge dangerous and destructive to the lives and properties of his Majesty's subjects." Now, the evidence brought forward in support of this preamble proved no more than that in the course of the preceding twenty years, seventeen lives and four thousand pounds' worth of property were lost by accidents at London Bridge -accidents, too, which were not all attributable to the piers and starlings, many of them being caused by inebriety and carelessness. The evidence failed besides entirely in showing that it was 22 the by the "starlings and piers,' 66 great fall of water at certain times of the tide" is "occasioned"-the superior height of the bed of the river above bridge having more to do with the fall than either. The evidence, in short, proved this only-that the preamble was all a sham. We seldom hear, nowa-days, of accidents at London Bridge, and for a very plain reason-there is no longer any bridge-job to be promoted. Had a concern for the navigation of the river been really the governing motive of the projectors and promoters of the new bridge, they would have considered it their duty to look at the effect which the old bridge, with its piers and Report of Committees of the House of Commons, 1820-1821. starlings, has on the navigation, in all points of view, and not have seized with such avidity on a few shreds of evidence, bearing only on a particular aspect of the case. They would have inquired whether these much-inculpated piers and starlings did not cause something else besides a few" moving" accidents to his Majesty's subjects; whether they did not, by obstructing and suspending the return of the water at each ebb of the tide, make the river ten times more valuable to all that part of the metropolis above the bridge, than it would otherwise have been; and whether, in fact, it was not absolutely essential to the general prosperity of the trade of the upper part of the Thames, and to the very existence of much of it, that the dam thus accidentally (perhaps) occasioned, should be permanently maintained. But why do we say they should have inquired into all this? They did worse than not inquire; they had it incontrovertibly proved in evidence before them that the navigation above bridge would, in truth, be ruined by the substitution of any new bridge which was not accompanied by some plan for maintaining the old dam; and yet they acted just as if no such evidence had ever been tendered! First of all, there was the evidence of the celebrated Smeaton-a higher au thority than whom in matters of this sort never existed-who laid it down as a matter of perfect certainty, that "if London Bridge were to be taken away, the river would become so shallow above bridge at low-water, that the navigation would be greatly impeded for hours each tide.”* the Next, there was an elaborate Report from Mr. Telford, who stands by universal consent at the head of living engineers, in which he showed, 1. That were the old bridge removed, velocity of the ebb above bridge would materially increase, and the time of low-water be earlier than at present.' 2. That the "navigation which is now practicable up to Teddingtont would that place." cease too early near 3. That "the bed of the river would be left nearly dry for several hours in the latter part of the ebb." 4. That though these evils would in part be remedied by "the increased velocity and momentum scouring away the mud, sand, and "Smeaton's Reports," vol. ii. p. 23. + Said to be so called (Tide.end-town) from its being the farthest point to which the tide extends. |