rotations cannot be applied, it becomes necessary next to inquire in what manner the apparent motion of the plane will manifest itself on the graduated table at any latitude. This inquiry, however necessary, has not yet been entered into by any of the writers on the subject, their mode of investigation having for its object to show the exact motion of the plane on the horizontal table itself. In an inquiry into the effect of the motion of an invariable plane on the horizontal table, it is necessary to bring into the calculation the inclination of the horizontal plane to the plane of rotation, and the direction of its inclination, as it is the projection of the apparent equable motion of the plane of vibration on the equatorial plane upon the horizontal plane that is required. This we have no occasion to calculate, for it is already provided to our hands in the motion of the shadow of an hori zontal sun-dial: the number of degrees and minutes for every hour of the dial being the distances for every corresponding hour of the apparent motion of the pendulum's plane. It will not be necessary to illustrate this further, as the slightest consideration will be sufficient to show the analogy of any invariable plane intersecting the plane of rotation with the shadow of the stile of a sundial, which is always parallel with the pole of the earth. For the latitude of London, the distances will be as follows: 1st Hour from the North both ways 11° 51′ .... would be slightly in favour of these views. Then the experiments at Dublin showed that the rate of motion varied, being least between the north and east and greatest between north and west, but the amount of difference is not stated; this also in some slight degree supports the views here stated. It must, however, be clearly admitted that no experiments have been reported that sanction in any degree the rate of motion in an east and west direction which these views require. Perhaps more accurate measurements of the angular motion in all directions may open up some further views, either more clearly to confirm the received theory or to point out more distinctly where it fails. If any experiments could show decisively the effect said to be produced by the little instrument invented by Professor Wheatstone, or even if full reliance could be placed upon the reported performance of that instrument itself, in all positions, the question would be at an end. In matters of this sort any theory not supported in all points by experiments applied successively to meet the difficulties of the question must be given up. No deduction of the reason from other facts and laws can stand comparison with the induction of a sufficient number of the special facts of the case. My wish being only to elicit truth, I have abstained from any harsh expressions or anything like a sneer at what I may consider unseemly airs assumed by some writers on this subject. Leicester, June 24, 1851, B. ROZZELLL. 2nd 3rd 4th 5th .... .... .... .... 12° 28′ .. 18° 54′ 6th ending East and West The apparent motion of the plane of vibration, if invariable, on an horizontal plane for each direction, as stated above, is the true quantity derived from the equable motion of the earth of 15° per hour, as certainly as 15° itself would be the quantity at the poles, It only now remains to inquire how far experiments sanction either view. In neither case are they decisive. Generally they are represented as giving an uniform motion rather more than the sines of the latitude require; and if the experiments have been mostly confined to a direction nearly north and south, as there is reason to think probable, it THE PATENT-LAW AMENDMENT BILL"NO. III." On Tuesday last Earl Granville laid before the House of Lords, from the Select Committee on the Law of Patents, a new bill, dubbed "No. 3." Our readers will recollect that there were already two bills in the field; namely, "No. 1," proposed by Lord Brougham, and "No. 2," brought forward under Government auspices. In the course of the discussion which took place on the present occasion, Lord Brougham observed, that "letters had reached him by scores from persons complaining that he had abandoned his bill about patents. Now his noble friend (Lord Granville) knew that he had not abandoned his bill, any more than he (Earl Granville) had abandoned his. Both bills were referred to the Committee, and the principal provisions of each-with some important additions suggested in the Committee-had been mixed up and amalgamated, as it were, in the measure before the House." This we find, on a comparison of the three bills, to be about the real the case; and as we have already laid the principal features of bills "No. 1" and No. 2" before our readers, we shall now confine ourselves to the "important additions" introduced by the Select Com mitteep state of These are; first, the entire exemption of the colonies from the operation of patents; and second, a provision for the advertisement of every application for a patent, in order that all and sundry may have due incitement to oppose the grant of it. Lord Brougham characterized these as " improvements," and the Select Committee are stated to have approved of them "unanimously." We humbly presume to think that they are, on the contrary, prodigious blemishes, and such as, if persisted in, must prove fatal not only to the bill No. 3, but to the whole set of bills. We did not altogether like either No. 1 or No. 2, but as both provided for the consolidation into one, of the three patents for England, Scotland, and Ireland (now so absurdly separated), we were willing, for the sake of so great an improvement as that, to overlook all minor objections, and well content that either bill should pass. If, however, the consolidation of the three patents is to be accompanied with the exemption of the whole of our colonies and foreign possessions from the operation of patents altogether, if the rights of inventors are only to be protected at home, and piracy of inventions is to be legalized throughout the whole of the foreign possessions and dependencies of the British Crown, and if, moreover, a legal obstruction unheard of before is to be interposed against the grant of patents even for the mother country, then we must say that the advantage of consolidation would be dearly earned at such a price. The exemption of the colonies is one of the most whimsical and irrational legislative projects which ever came under our observation. Lord Granville did not assign a single reason for it, and we defy him to produce a good one. The plan of advertising for opposition to patents is not much better. It is a plan conceived in the interest of the law-officers of the Crown (or rather of certain new functionaries proposed to be appointed by the Tertium Quid Bill, -but wholly unjustifiable on grounds either of public policy or of private justice. Both clauses are manifestly dictated by a spirit altogether adverse to patents and to the rights of inventors. The exemption of the colonies and foreign possessions is but a first step towards the utter extinction of patent rights throughout the whole of the British Empire. Indeed, Earl Granville and other lords frankly confessed that they were opposed on principle, to the system of patents altogether, and that in trying to amend the existing system, they but yielded to a conviction that the general sense of the country was so far against them, and called for amendment onlynot abolition. Inventors and patentees will now see, therefore, what they have to hope for at the hands of Government. The Bill, "No. 3," has still to go through the Commons, and it must be therefore opposed most promptly and vigorously, if inventive genius is still to have a place in this country among the sources of individual advancement and national prosperity. We shall return to the subject in our next. THE FIRE AT LONDON-BRIDGE. A person of the name of Finlay was the first who discovered the recent disastrous conflagration at London-bridge, and the first to enter the building after the fire had broken out. According to the Times of the 26th instant, he in evidence said, "His opinion was, that had he had a few pails full of water at hand when he first entered, he could have extinguished the flames, or have kept them under till the arrival of the engines." Evidence to the same effect has been given on many previous occasions when the outbreak of fire has been inquired into, and the simple means by which a ready supply of water could be insured in the interior of large buildings has been for half a century exemplified in Portsmouth Dockyard. Disregard of the example there set, affords one amongst many instances of the immense length of time requisite to induce any general adoption of useful inventions, and hence the need arises for reiterated calls of attention to them, as is now done to the fire-extinguishing work in the same dockyard. It is not exaggeration to say that property to the amount of millions of money would ere this have been saved, had similar ones been very generally adopted for the preservation of buildings from the ravages of fire. the sides of the guard, it shuts the flaps which are exposed to its action, and opens those on the opposite side or sides for the escape of smoke for maintaining the draught of the chimney; and in the second place, the close cover at top at all times prevents any down draught and smoking from that cause. This disregard of the Portsmouth example has not arisen from any want of publicity of the means employed, since, perhaps, no industrial establishmentthe Crystal Palace excepted-has ever been resorted to by so great a multitude as the wood-mills in that Arsenal, and those visitants must have had little observation who failed to notice the waterpipes always full, the hose, the buckets, all prominently distributed in every chamber ready for instant use. In the case of the recent conflagration, had even a single such water-pipe been provided with appropriate hose and buckets, and communicating, as at Portsmouth, with a cistern of water on the roof, Finlay, there is every reason to believe, would have been enabled to save property to the value, it is said, of 200,000/. Neither has disregard of the Portsmouth fire-extinguishing works arisen from a want of public information respecting them through the press. Though official communications be usually confined to office, yet Sir Samuel Bentham, in whom the Portsmouth works originated, having given a short description of them in his official "Statement of Services," 1813, printed and largely distributed copies of that communication at the time, and afterwards published it: since then, descriptions of them, more or less ample, have been given in the Mech. Mag., Nos. 1268, 1355, 1369, 1439, and also in the Builder. One of Sir Samuel's applications of well-known facts to useful purposes was that of the fusibility of a compounded metal at the heat of boiling water. As a calometer fusible metal appears in No. 1429 of the Mechanics' Magazine; he introduced it as a safety-valve in the cooking and water-distilling apparatus of the Arrow, 1797; and in the Builder it has been proposed for plugs to close water pipes, as an important part of arrangements for the preservation of deeds and other manuscripts in cases of fire. So in buildings, especially those containing stores liable to spontaneous inflammation, it might be desirable to form portions of interior water-pipes of fusible metal, which, without the intervention of man, would melt, and introduce a body of water immediately when the surrounding heat rose to 212 Fahr. The Times, some months ago, mentioned a fact which proves that such a provision for the immediate application of water is far from a visionary speculation. The paper related, that on the outbreak of fire in the basement storey of some house in the city, the leaden water-pipe in the back of the building was found to have melted by the surrounding heat, and that the water thus admitted from the house cistern had been sufficient to extinguish the flames. Should fusible metal be introduced for the purposes indicated, experiment would be requisite to determine its power of resisting pressure, as on this the necessary thickness of water-pipes would depend. Indeed, so little use has hitherto been made of this composition, that its properties, other than that of possibility, are little known: nor does it seem that mixtures in different proportions of the several metals composing it have been tried with a view to ascertain at what different low temperatures a compound metal might be made to melt. It will be seen, in some of the numbers of the Magazine above referred to, that by slow degrees the fire-extinguishing works at Portsmouth are being imitated. They have lately been so, to a certain extent, at the British Museum, -Mr. Braid wood (it is understood) having visited the dockyard, there to examine them: they are said to be provided for the security of the Crystal Palace, and are thus likely to attract attention; but their adoption would be most likely to become general were some private civil engineer to devote himself to the fireextinguishing branch of the profession: it would lead as much to his own emolument and credit as it certainly would to public benefit. Private interest is far more efficacious for the introduction of improvements than any representation of general good ever has been, or seems likely ever to be. There are various precautions in respect to the construction and application of buildings, which would, if observed, doubtless be productive of much security against conflagration; some have been already particularized in the above-quoted numbers of the Magazine. One measure which Sir Samuel was exceedingly desirous of introducing in naval arsenals was, that of storing all particularly inflammable matters in under-ground compartments, and, when near a river or the sea, below the level of the water, so that it might be let into and submerge any one compartment, without damage to goods in other stores. The store cellars of his contrivance, over the reservoir in Portsmouth Dockyard, were perfectly well ventilated and dry. He would probably have recommended the stowage of rags in such compartments, appropriating the upper floors of a warehouse to less inflammable substances. He had at different times long official controversy as to a more appropriate arrangement of stores in naval arsenals; in them it was merely official habit that had to be overcome; in the case of private storehouses their proprietors naturally look to the appropriation that will best pay, yet still a classification of stores, in respect to inflammability, would be very useful, having regard also to other sources of deterioration than fire. There would be the head of highly inflammable storesstores not easily ignited-stores injured by moisture-those which bear dampness with impunity, and so forth. Merchants, it is true, possess general ideas as to the kind of storehouse that suits well their commodities respectively, yet such a classification would lead to beneficial results; it would probably be found that many articles now consigned to cellars would be better above ground;-that existing warehouses are not provided with a sufficiency of underground accommodation for inflammable stores ;that little or no regard is had to the due ventilation of cellars, still less to their being made dry-a condition much to the present purpose, since neither rags nor hops could be kept in a moist atmosphere, consequently must continue to be stored in upper floors, though it should lead to such destructive conflagrations as that which is now deplored. July 2, 1851. BUTCHER'S REGISTERED SELF-ACTING CHIMNEY-GUARD. (Mr. William Butcher, St. James's-place, Bermondsey, Proprietor.) M. S. B. Fig. 2. THE PROSPECTS OF ELECTRO-MAGNETISM A writer, referring to my preference for the rotary form of the engine, says, I have "fallen back upon Davidson's and Avery's plans." As to Davidson's engine, it was fully tested by myself on a large scale in Boston, in 1837, and it was invented and tried in Baltimore by Dr. Edmondson, in 1834. [See Silliman's Journal.) But the writer misapprehends the case. I have "fallen back" upon no one. The rotary form of the axial engine, as well as the reciprocating, differs most essentially from any engines ever before tried. In my reciprocating engines, the magnetic piston, if I may so call it, is impelled with nearly an equal force throughout the stroke, and this for any length of stroke desired. The rotary axial is the perfection of the improvement, and does not seem to involve the difficulties inherent in rotary steam engines, for my pistons require no packing. When the description of my engine is published, which will be ere long, I think the writer referred to and others will appreciate its peculiarities. I have never claimed for electromagnetic power that it is or would be superior to steam, that is, in every respect; nor is it necessary that it should be, to answer the purposes of my investigations. The cost of the power has been with me a subordinate question, knowing full well that other more important questions had to be settled first, before ever the cost could be fairly ascertained. The abstract rule laid down by M. Joule, Messrs. Hunt, Scoresby, Oersted, and others, of the absolute duty performed by a given quantity of zinc, is well enough as far as their experiments went; but is of little or no value in the practical question of the availability of this power. To illustrate my meaning, take the highest duty of coal in the best condensing engines in the world; will any one pretend to say that there is no room for improvement even there? Why, in the Cornish engines, within a few years, the expense of a horse-power has been reduced from 10d. to 2d. per diem. But suppose it be ad mitted that the minimum cost has been attained, how many engines in the world can be worked as cheap as those engines? In reality, M. Joule's calculation makes the expense of magnetic power less than is steam power at the present day in some of our locomotive engines. The cost, therefore, I say, is not the practical question; and if the magnetic power will cost more than the dearest steam power, still, if we render it an available power in other respects, it must come into use for many and perhaps most purposes, by reason of its great advantages over steam in point of safety, simplicity of construction, readiness for operation, compactness of machinery, and, lastly, one very important condition, namely, there need be no consumption of material when power is not wanted for use. Magnetism, it is yet in its infaney, and steam is full grown. The proper appreciation of magnetic power is to be had by comparing it with steam in an equal stage of its development, when it will be seen that the magnetic power rather carries the palm. Steam power has not yet reached its climax, but it seems as if it were approaching its culmination, as its march seems to be comparatively slow; while magnetic power, evidently in its inception, is progressing rapidly. The first steam locomotive applied in England, in 1804, made, on a level plain, five miles an hour with about 15 tons; and ten years after, the celebrated Mr. Stephenson constructed a locomotive which was considered a great improvement, and carried eight carriages, about 30 tons, four miles an hour, and in 1829, after twentyfive years of experience (and all the while "invention was stimulated by necessity"), Mr. Stephenson produced his locomotive, the "Rocket," which made an average speed of fifteen miles an hour, with 17 tons, consuming about 1 lb. of coke per mile to a ton, as in the two trips of seventy miles 1,085 lbs. of coke were consumed. With my magnetic locomotive just as it is, I would willingly have entered the list with the "Rocket" in point of power, speed, and expense of working. I feel confident, however, that the magnetic locomotive is capable of carrying two loaded passengercars to Baltimore, at the rate of twenty miles an hour, as soon as some of the very great and obvious defects are remedied. I had lately an opportunity of seeing how great was the friction of the machinery of the locomotive. They have at our station here, one of the largest and strongest horses I ever saw, and he is well trained to the work of pulling cars. In removing the magnetic car from its station, this horse was |