384 MINUTES OF EVIDENCE ON THE PATENT-LAWS. Do not you think that the multiplication of patents to a great extent would be a great impediment to inprovements in machinery and the arts ? -Yes, Have you known any instances of patents for small things which have stood in the way of improvements ?— I cannot call any to mind at present. Are not workmen and people of that description constantly in the habit of making little observations and small improvements?-Yes, sometimes very important ones arise from the workmen. If a workman has discovered any thing of the kind, and finds it likely to be beneficial, there is no difficulty in procuring any one to join him in the expense of taking out a patent for it (???) Do you not think that if it became a habit among that class of people to secure patent rights for those smalf discoveries at low rates, it would be very inconvenient? I think very much so. You mean to say that between 300/. and 4001. is not too great an expense for a patent for the three kingdoms? -No: I should think it would be no worse if it were a little more; it bears no proportion to the expense of completing a machine, or of defending it when infringed. Have you ever considered whether it would be inconvenient to inventors to have their specifications sealed and concealed from the public?-I think it would be an inconvenience. I think it would not be a proper thing towards those engaged in the same line: there may be things sealed which other persons may be pursuing with vigour and expense. I think after it is once secured, the more public it is made the better. Professor Millington, examined. Agrees with the preceding witness as to the evils arising from the generality of the titles of patents, and the advantage that would be derived if inventors were obliged to be more particular. But even now the passing of a patent may be opposed successfully on the ground of the vagueness of the title. Has known many instances of a title refused by the Attorney-General because it was too general. There are so many vague titles, because there is no objection made to them under caveat, or in any other way. A short time ago, a Mr. Wollams applied for a patent for the improvements in carriages; that was sent back again because it did not state in what part of the carriage the improvement was to be. Admits that as the law now stands, if an inventor were to state his inven tion very precisely in the title, he would be exposed to the chance of hav• ing the invention discovered before the sealing of the patent; but would assimilate our law to that of France, where the specification is lodged in the first instance, the invention is secured to the patentee from the date of his application; and he is allowed, for a tritting fee, to amend his original specification as often as he may see proper. Does the specification undergo much examination before the commissioners in France ?-It does not appear to me to undergo any, because I have known them enrolled with imperfections, and they pass them without difficulty. After a specification has passed that commission in France, are the public at liberty to question it in a court of law upon any doubtful point?—They are precisely as in England; there is this difference only, that in France the infringement of a patent is penal, which is not the case here. la England it is a mere question of damages; but in France it is penal to evade a patent, and the spurious articles are burnt by the hangman. Are you aware whether or not specifications in France are concealed from the public?--I am not. In England, 1 believe, they can only be concealed by authority of Parliament, and there have been instances with us of concealed specifications. [From our anxiety to include every thing which has the least practical bearing on the questions raised by this Inquiry, our abridgment of this evidence has extended to a greater length than we anticipated. The completion of it we must reserve for our next Number.-ED. M. M.] INTERIM NOTICES. Communications received from A—Mr. Rickard-Mr. Massingbird-Mr. Harrison-B. 9.Mr. Davy-Y. P.-Mr. Collins-A Reader at Lincoln-Inquisitor. Erratum.-In a few copies of the first sheet of this Number, the two notes at the bottom of p. 365 have been transferred by mistake to P. 368. LONDON: Published for the Proprietor, by M. SALMON, at the Mechanics' Magazine Office, No. 115, Fleet Street; where Commanications for the Editor (post paid) are requested to be addressed. M. SALMON, Printer, Fleet Street. BRIDGES OVER THE THAMES. DESCRIPTIVE ACCOUNT OF THE PRINCITAL BRIDGES ERECTED OVER THE RIVER THAMES. BY MR. C. DAVY, ARCHITECT. 2 No. 6.. -PILE-DRIVING. (Continued from p. 307.) The ordinary machine described- The ordinary pile-machine, represented by fig. 4, is composed of two upright grooved posts B, supported by side braces GG, fixed upon the sole F, and attached to the back stay E; this is connected above to the two uprights, and below to the forked framing H, also secured to the sole F. The ladder for mounting to the top of the machine is constructed in a very simple manner; namely, by passing wooden pins through the back stay, as will be seen in the engraving. The ram A, destined to drive the pile D, is generally a large block of wood, bound with iron at top and bottom to prevent it from splitting. It has two tenons or ears stopped with keys, driven in behind for the purpose of 1.keeping it between the grooved posts. There is also a ring to receive a hook, K, fastened to two cords, each passing over a pulley placed at the top of the two uprights. The weight of a wooden ram is generally about 800 lbs.; so that twenty men pulling downwards, by as many ends of cords C attached to the two main ropes, may afterwards let it fall by its own gravity upon the head of the pile, which is repeated, blow after blow, as many as twenty-five or thirty times. Those who conduct the gang, after having counted the percussions, cry au renard," which is the signal for the workmen to take breath: this being accomplished, they commence another "volée,"- -a name given to the twenty-five or thirty consecutive blows; and thus alternately, until the pile refuses to be driven any further. The machine is then removed elsewhere to proceed with the driving of other piles. When we examine with a little attention the machines that have been chiefly used, it seldom happens that we find them constructed in such a manner as to fulfil perfectly their object, being almost always deficient in their essential parts, and producing considerably less effect than they might be made to accomplish. Ancient as the machine of which we are now speaking is, and notwithstanding so many able men have employed it at all times, it is only within a few years that it has been in any way improved. To judge of the merits of our modern improvement, it will be well to examine in what manner the workmen produced the action of the ram. A man using a cord, in order to raise a weight by the assistance of a pulley, in drawing downwards vertically, only exerts a raising power equal to the excess which the weight of his body bears to the weight to be raised: from whence it follows, that a man can only lift, by continually renewing his exertions with the assistance of a pulley, a weight equal to that of his own body, however strong he may otherwise be. Upon this we may remark, that in raising the arms to lay hold of the cord, and afterwards bending himself as low as is possible, he can scarcely raise above 70 lbs.; which is about half the weight of his body, commonly estimated at about 140 lbs. We have supposed the cord to be drawn vertically; for if it were drawn sideways, the weight of the body applied to it will decrease as the obliquity increases, taken with regard to the action of the weight of the men, and not of the weight to be raised; since by a property of the pulley, the arms of the lever are always the same. To apply this reasoning to the machine in question-you are to consider that the ten men who are exerting their powers at the ends of cords answering to the main ropes I L, can only draw obliquely with respect to the vertical line IN, and the same also with respect to the main ropes IL; since in both cases they make a circle, in which those who are opposite to the others destroy reciprocally a part of their action, which is here an inevitable defect: since it is necessary that the ten men should be placed in a ring to act together. It is not the same with the obliquity IL; this may be applied in a more vertical direction, by passing BRIDGES OVER THE THAMES. the cord M, I, L, over a wheel 4 or 5 feet in diameter, instead of which the diameter of the pulley seldom exceeds 10 or 11 inches; therefore there is no doubt that instead of the 40 lbs. each of the twenty men is supposed to borrow from the weight of his body to raise a ram of 800 lbs., he can only exert nine or ten at the most upon the whole quantity. This fact is confirmed by experience; for by employing a wheel instead of pulleys, sixteen men can raise the same ram of 800 lbs., each being able to exert a power of 50 lbs. It remains now to be shown in what manner the machine is to be constructed, to supersede the use of pulleys by means of the wheel. By referring to figs. 5 and 6, will be seen the plan and side-view of the apparatus. To render the pile-machine susceptible of the preceding advantage, it is only necessary to modify the top part to effect it; I have therefore only shown that portion for the purpose of explanation. A marks the two grooved uprights, crowned with a cap B; each of the posts is connected with a piece placed horizontally three feet under the cap B: these pieces are fastened together by a cross-quarter of timber, supported by the back stay G, which is fixed in such manner as not to obstruct the placing of the wheel E F, which has its nave pierced with a square iron, from which the trunnion or axle projects, and rests upon its bearings D. More steady action and solidity is gained by this method, than if they were not united with the square iron inserted in the nave of the wheel. This wheel I have supposed to be about 4 feet 6 inches diameter, measuring from its channel, and distant from the posts A about three feet. This arrangement enables the workmen to operate with greater facility, having more room for placing themselves in a ring, and enabling them to pull in a more vertical direction at the other end E H, which answers to the ram-the more so, as the back stay and ladder G not being in the -way, the sixteen men are employed in pulling only one rope, and not divided into two separate bands-the action in the latter case never being perfectly alike. Another advantage to be de 387 rived from the wheel is, that there is only one movement required to counterpoise it-about one-third of the circumference of the wheel for each blow-it becoming greater by the acceleration that the ram acquires. The pulley on the contrary, in consequence of the smallness of its diameter, makes. nearly two revolutions when the ram rises or falls, thereby causing more resistance on account of the stiffness of the cords.* We may also add, that the same cords or ropes are not so soon worn out with the wheel as with the pulley; since it is known that in working one will last as long with the wheel, as three will with the pulley. M. Pollast, inspector-general of the bridges and roads of France, having improved in this manner the machines that he used in the construction of the bridge of "Poissy sur Seine" in 1747: he found them to answer so well, that he reduced the former brigades or gangs of workmen consisting of twenty men to sixteen, performing the same work. The foregoing observations, which I have chiefly extracted from M. Belidor, may be applied with equal force to the various modifications of pile-driving machinery hereafter-mentioned, and in the choice of them considerably guide the judgment. The same writer proceeds to give an estimate of the time and expense necessary for the driving a number of piles into earth containing four different stratas: his remarks in this respect are not only verbose, but totally insufficient for the present practice; for these reasons I shall decline inserting them, and as a conclusion to this paper add a few General Remarks. With the present machine a pile may be driven with great expedition, as it is effected by a series of smart shocks given in succession. The workmen should, however, take advantage of the rebounding of the ram Belidor, Art. 308. + M. Belidor supposes, in the first place, that the pile is to be driven in sixteen feet, and through four different strata, each pile, accord ing to his estimate, occupying in time 3h. 5m. 345., and the average expense of each, 6 liv. 10 sols, 8d. Lastly, that six piles can be driven with the aforesaid machine in twenty-four hours. 66 Sir,-Observing in the newspapers the description of a new conveyance for heavy, goods,"* I am induced to send you a rough sketch of the carts in common use in Guernsey and Jersey, whence I returned a few days ago, and of which the machine described in the papers appears to be only a bad copy. The platform in this cart is considerably longer than that of a common cart, I think it cannot be less than seven feet; for I frequently saw two Alluding, we presume, to that recently introduced in London by Mr. Wilberforce, Jun. casks of tallow on one which did not Occupy the whole of it. The wheels are not higher than those of common carts; those, of the "conveyance" alluded to are described as seven feet high; they must, therefore, be much heavier and more cumbersome than is necessary. The body or platform is not more than a foot from the ground. But what struck me most in the construction of the Guernsey carts, was the ingenious contrivance for loading and unloading particularly heavy casks, such as hogsheads of sugar, tallow, &c. |