32 CHEAP AND EASY METHOD OF MAKING SODA WATER. Shells may be made in a similar manner, which by their momentum will destroy defences, that are impregnable at present; and which will burn ships that are secure in their harbours, because they are beyond the range of all the mortars that are in common use. There are four practical maxims in books of artillery which render the above proposal so promising, that it would not be unworthy perhaps of the Board of Ordnance to extend a few experiments, that have been made with only a six-pounder, to guns and mortars of the largest size. First Maxim. All practical writers agree," says Robins, (vol. i. p. 146.) "in making the range of a twenty-four pounder, with the greatest allotment of powder, and at an angle of 45 degrees less than three miles." St. Remy informs us, that the range of a twenty-four pounder, 10 feet in length, with a charge of 16lb. of powder, and at an angle of 45 degrees, was 2250 French fathoms, which is about 444 yards less than 3 English miles. Second Maxim. By an extract from the books of practice kept at Woolwich, it appears that a 13-inch mortar, at an angle of 45 degrees, and charged with 30lbs. of powder, throws 121 inches in diameter to the distance of 3350 yards, the shell weighing 231lbs. and being nearly four-fifths of the weight of a solid iron ball of the same diameter. Third Maxim. With proportional quantities of powder, and at an angle of 45 degrees, heavy balls range to a much greater distance than small ones. A thirty-two pound ball, for instance, will range near half as far again as a nine pound ball, their diameters being to each other nearly in the proportion of six to four. Fourth Maxim. The range of a ball projected at an angle of 15 degrees, is half the range of the same ball, if projected with the same force at an angle of 45 degrees.-See Muller's Artillery. Now, by the above experiments, the range of a spheroid thrown by a sixpounder with 4lbs. of powder, and at an angle of 15 degrees, is 3200 yards, which at an angle of 45 degrees, is, by the fourth maxim, 6400 yards, that is, more than three miles and a half; and, by the third maxim, the range of a spheroid from a thirty-two pounder, will be near six miles; which, by the first and second maxims, is double the range of balls that are thrown from the same guns. [The preceding experiments are singularly at variance with the statement which we quoted in our last number from Colonel Macerone's unpublished work, particularly as regards the range of spheroidal balls, compared with the common circular shot. Perhaps Col. M., or some other of our military readers, will favour us with an account of these "subsequent experiments" which have demonstrated the fallacy of Professor Anderson's. It is observable that the spheroidal ball with which the Professor made his experiments, was in each case double the weight of the circular shot with which it was contrasted. But ought not the weight as well as all other circumstances, to have been precisely the same, to make the comparison accurate?]-ED. CHEAP AND EASY METHOD OF MAK- Take forty grains of the carbonate of soda, put them into a common soda water bottle, which generally contains about ten ounces of water. Immediately afterwards, put into the same, thirty-five grains of tartaric acid, then cork it quickly. The acid and the salt ought to be used in crystals, as when in powder they are apt to seize upon each other before the bottle can be well corked, and so a considerable quantity of the carbonic acid gas which is evolved is lost. INTERIM NOTICES. We hope all that T. tells us of a projected reform in the London Mechanics', Institution, may prove true. It is possibly, not yet too late to save it from rain. ... The design of a Tractable Balloon, published in our 313th number, should not have been subscribed "P. B.," but "A. P.," the initials of Mr. A. Peacock, the author of this and many other ingenious contributions to our pages. Communications received from Mr. Clampit G. S.-W. A.-Petrus-Nauticus-J. B. C. -R. T.-J. G. N.-S. Y.-A.Sincere Friend→→ J. O. B. PATENTS.-Persons desirous of assistance in taking out Patents for Great Britain and Ireland, or for any foreign country, may obtain the same on moderate terms, by application to the Editor, either personally, at the Mechanics" Magazine Office, or by letter, post-paid. LONDON: Printed and Published for the Proprietor, by M. SALMON, at the Mechanics' Magazine Office, No. 115, Fleet Street; where Communications for the Editor (post paid) are requested to be addressed. Mechanics' Magazine, MUSEUM, REGISTER, JOURNAL, AND GAZETTE. No. 318.] SATURDAY, SEPTEMBER 12, 1829. [Price 3d. "All things without us, nay I may add, all things on us; are mere elements; but deep within us, lies the creative force which out of these can produce what they were meant to be; and which leaves us neither sleep nor rest, till in one way or another, without us or on us, this has been produced."-GOETHE. 34 A OLD LONDON BRIDGE. DESCRIPTIVE ACCOUNT OF THE BRIDGES OVER THE THAMES, BY MR. C. DAVY. No. 2. OLD LONDON BRIDGE. Architect-Peter of Colechurch-date 1176. In the introductory paper on this subject, mention was made of the great variety of beautiful combinations of which the arch forms the basis, and by means of which architecture has been freed from the stiffness and monotony inseparable from an exclusive use of forms made up of straight and angular lines. It will be remembered that in the classification of this variety, the first list exhibited those combinations included under the Italian or Roman style; and the second, those which fall under the denomination of Gothic. The latter are so much more numerous and interesting than the former, as fully to justify us in awarding to our Gothic ancestors, the palm of a decided superiority in this branch of construction. It was only, however, in the erecting of ecclesiastical and baronial buildings that they evinced their skill in this respect; for, strange to say, there is manifest in all their attempts at bridge building, nearly a total neglect of those capabilities of the arch, of their intimate acquaintance with which, they left us so many other proofs. In our ancient cathedrals nothing is so remarkable as the general loftiness of the arches; but, in the old Gothic bridges, scattered throughout the country, the arches are almost always so near the water as to prevent any navigation from being carried on, and where the height or rise is considerable, a sub-arch is generally introduced in the intrados or soffit a circumstance particularly observable in Old London Bridge, in some of the lesser arches (see fig. 1 and 2.) The pins, too, were seldom of any relative proportion, London Bridge, containing at one time no less than 19 disproportioned arches, with piles equally clumsy and rude. The earliest account we have of a bridge being erected over the Thames, bears the date of the 10th century; but it is so obscure, that little reliance can be placed upon it. We have however the best of authority for stating that a ferry existed long prior to this across the river near the site of the present bridge; and that thes ferryman, one John Overy, and his wife, at their demise, left considerable! property which, by their care and f industry, they had accumulated, to o their only daughter Mary, together with the ferry itself. Mary Overy, it is said, converted this legacy and right to charitable uses, by establishing a House of Sisters near the church. At her death the property devolved to this house, and at its dissolution was converted into a college for priests, who built a bridge with timber. In consequence of the fre quent repairs which this bridge required, it was taken down, and by the I assistance of the citizens of London, rebuilt with arches of stone, which was the first time the River Thames : was first graced with a bridge of any importance.* It is evident, that for a long time, the art of bridge-building was little known in this country, for, although ! the bridge is stated to have consisted of "arches of stone," the major part of the superstructure, including the roadway, cut-waters, or starlings, &c.; a and that portion of the bridge now oc-s cupied by a balustrade, was wholly of timber. London Bridge was not erected for the sole purpose of forming a com munication with Southwark, for we› find that in the early part of the 11th century, it was used for defensive purposes, and regularly fortified with towers, ramparts, and castles. It i was in 1008, the scene of several engagements, in which Etheldred t the 2d. and Olaff were victorious over the Danes; but, in the last of these conflicts, it broke down. It is a curious fact, that although this took place in 1008, another bridge of wood is mentioned as being placed across the Thames, at this part, in 1016. In 1091, it was again des troyed by flood and tempest, but shortly after rebuilt. In 1136, it was considerably injured by fire, but ON INVERTING THE SLIDE IN THE GAUGING Rule. repaired. In 1163, it was rebuilt of timber by Peter of Colechurch, who, thirteen years later, laid the foundations of the present stone bridge, which was completed in 1209. The architect died three years before its completion, and was buried in a chapel, in the centre pier of the bridge. The bridge, at this time, was covered with houses, which were in their turn consumed by fire in 1212, when upwards of 3000 people perished. In the winter of 1282, five of the arches were destroyed by the ice, and again repaired. In 1437, the principal gate on the bridge, (Southwark side) fell down, and carried with it two of the arches; and in 1471, Thomas Neville, in an attack upon the bridge, burned another of the gates, and a number of houses. In 1553-77 and 79, it was repaired and refortified. In 1633, 43 houses on the bridge were destroyed by a fire, which broke out near the church. In 1646, it was repaired, and the 43 houses rebuilt. In 1665-6, it was damaged severely by high wind. In 1666, the great fire destroyed the houses that were rebuilt in 1646. Between the years 1666 and 1686, nearly the whole of the houses were pulled down and rebuilt. In 1725, the gate-house was injured by fire, and, in 1750, the bridge assumed the appearance shewn in fig. 1, which however exhibits only 6 out of the 19 arches. In 1756, an Act of Parlia ment was obtained to clear away all obstructions and widen the arches by the removal of some of the smaller ones. When these improvements were carried into effect, they left the bridge nearly in the same state in which it now is, as represented in fig. 2, which exhibits the centrerch and two small arches. Having now briefly mentioned in chronological order the more remarkable events in the history of this interesting structure, I beg to refer the curious reader for farther details of these events, to the following works:- Stow's Survey, Brayley's Londiniana, and Thomson's Chronicles of London Bridge. I shall in my next describe the construction of the old bridge, and 35 notice the reports of the committee appointed in 1820, for the purpose of taking into consideration the propriety of rebuilding the same. (To be continued.) ON INVERTING THE SLIDE IN THE Sir, I observe that your intelligent correspondent, Mr. Woollgar, at p. 23, of your last Number, refers to a paper in the quarto series of Nicholson's Journal, published in 1797, for the earliest notice with which he is acquainted of the important improvement in the use of sliding or gauging ing the position of the slider. I have, rules derived from inverting or revershowever, recently met with an earlier reference to that expedient, with which it seems a matter of justice that you should be acquainted. About three months ago, a new ed tion of that useful little book, Hutton's Compendious Measurer, was published by Dr. Gregory. Among the additions and improvements which relate to the use of the sliding rule. he has introduced, are some which He gives some examples to illustrate working with the inverted slide, and the advantage, in many cases, of to one of them subjoins the following note, p. 291: "This method of solving such questions, by means of the inverted slider, was published (first, he believes) by the editor of the present edition of this work, in No. 4, of Whiting's Mathematical Delights, in 1794; and, among the questions to exemplify it, was the example here given. He also then prepared and announced for publication, a Treatise on the Sliding Rule, containing the application of the same method to many other problems in arithmetic, amples given in this general scholium, mensuration, and gauging. The exare transcribed from the manuscript copy of that work, which its author preserves as a memento of early labour." I do not imagine that Dr. Gregory cares any thing about the reputation of introducing such an improvement; yet, if he be really the first who announced the method, which seems 36 FIRE-EXTINGUISHING MACHINERY. CIRCULAR LOGARITHMIC SCALES. Sir, Mr. Woollgar, in his communication in No. 317, p. 23, appears to me to have misunderstood the nature of my improvement in the construction of logarithmic scales. I proposed that the lines and numbers should be marked on the outside circumference, that is, on the rims of two or more concentric wheels revolving on the same axis. This idea, which occurred to me so long ago as the beginning of the year 1826, is, I conceive, essentially different from the marking them on the surface of a ring revolving round a circle, as they are in Mr. Lamb's Concentric Circular Proportioner. When I first thought on the subject, I was wholly unconscious of any attempt having been made either to mark the lines on the surface or on the rims of circular instruments: both plans were suggested to my mind nearly at the same time, but considering the latter to be the best, I devoted my attention to that principally. The superiority over Mr. Lamb's instrument, I consider, consists in the practicability of making them almost of any size, yet perfectly manageable, of using the lines reversed as well as direct, and of being able to bring any two lines into contact that may be wanted. At the time I wrote the communiIcation for the Mechanics' Magazine, (Nov. 1828) I could not have considered the giving it a circular form as a new idea, having read in the dissertation on the rise, &c. of navigation, prefixed to the admirable treatise by Robertson, that the Rev. William Oughtred projected the lines on Gunter's scale into a circular arch, shewing fully its uses in a treatise first published in 1633. I remain, &c. ANTHONY PEACOCK St. George's, East. Sept. 7, 1829. FIRE-EXTINGUISHING MACHINERY. Sir,-In my last communication (vol. xi. p. 357), I alluded to the great extent to which fire-extinguishing machinery had been provided in London: and also briefly adverted to some of the causes which prevent the public from receiving all the benefit and security they are calculated to afford. My intention, in the present instance, is, to resume that part of the subject, which not falling under the head of fire-escapes, I then purposely omitted; and also to lay before your readers some suggestions which appear calculated to increase the usefulness of that valuable machine, the fire-engine. I before noticed the irregular and unequal manner in which both fireoffice and parochial engines are scattered over this metropolis: and I may now add, that their sizes and construction are as irregular as their distribution. The want of something like uniformity in the connecting screws of the hose, if not in the size of the engines, has been a frequent cause of regret. One instance of this occurred a short time since at a fire in the neighbourhood of London. Two private engines, the only ones at hand, were brought, and one of them was quickly got to work: the hose, however, almost immediately burst, and the engine was disabled. Owing to a defect in the suction-pipe of the second engine, that could not be brought to bear upon the fire: which was, therefore, left for some time to rage with uncontrouled fury. Could one engine have appropriated either the hose or suction-pipe of the other, much good might have been done by one efficient machine. But, although the engines were about the same size, yet the screws being of different threads, this could not be done. To prevent similar occurrences in future, standard screws for the hose of fire-engines should be fixed upon, of three or four sizes, for first, second, and third-rate engines. Three sizes will I think be sufficient for general purposes. I would recommend the screws for second-rate engines to have a water-way of about two inches diameter: and this size to be universally |