that it shall draw unto it on a reclined plane a bullet of steel, which, still, as it ascends near to the load stone, may be contrived to fall through some hole in the plane and so to return unto the place whence at first it began to move, and being there, the loadstone will again attract it upwards, till, coming to this hole, it will fall down again, and so the motion shall be perpetual.” The fact that screens do exist whereby electrical and magnetic action can be cut off would seem to open a door for the perpetual-motion seeker. Unfortunately the bringing up and removing of these screens involves in all cases just that gain or loss of work which is demanded by the law of the conservation of energy. A shoemaker of Linlithgow called Spence pretended that he had found a black substance which intercepted magnetic attraction and repulsion, and he produced two machines which were moved, as he asserted, by the agency of permanent magnets, thanks to the black substance. The fraud was speedily exposed, but it is worthy of remark that Sir David Brewster thought the thing worth mentioning in a letter to the Annales de chimie (1818), wherein he states “that Mr Playfair and Captain Kater have inspected both of these machines and are satisfied that they resolve the problem of perpetual motion.”
The present writer once was sent an elaborate drawing of a locomotive engine which was to be worked by the agency of permanent magnets. He forgets the details, but it was not so simple as the plan represented in fig. 4, where M and N are permanent magnets, whose attraction is “screened” by the wooden blocks A and B from the upper left and lower right quadrants of the soft iron wheel W, which consequently is attracted round in the same direction by both M and N, and thus goes on for ever.
One more page from this chapter of the book of human folly; the author is the famous Jean Bernoulli the elder. We translate his Latin, as far as possible, into modern phraseology. In the first place we must premise the following (see fig. 5). (1) If there be two fluids of different densities whose densities are in the ratio of G to L, the height of equiponderating cylinders on equal bases will be in the inverse ratio of L to G. (2) Accordingly, if the height AC of one fluid, contained in the vase AD, be in this ratio to the height EF of the other liquid, which is in a tube open at both ends, the liquids so placed will remain at rest. (3) Wherefore, if AC be to EF in a greater ratio than L to G, the liquid in the tube will ascend; or if the tube be not sufficiently long the liquid will overflow at the orifice E (this follows from hydrostatic principles). (4) it is possible to have two liquids of different density that will mix. (5) It is possible to have a filter, colander, or other separator, by means of which the lighter liquid mixed with the heavier may be separated again therefrom.
Construction.—These things being presupposed (says Bernoulli), I thus construct a perpetual motion. Let there be taken in any (if you please, in equal) quantities two liquids of different densities mixed together (which may be had by hyp. 4), and let the ratio of their densities be first determined, and be the heavier to the lighter as G to L, then with the mixture let the vase AD be filled up A. This done let the tube EF, open at both ends, be taken of such a length that AC : EF > 2L : G + L; let the lower orifice F of this tube be stopped, or rather covered with the filter or other material separating the lighter liquid from the heavier (which may also be had by hyp. 5); now let the tube thus prepared be immersed to the bottom of the vessel CD; I say that the liquid will continually ascend through the orifice F of the tube and overflow by the orifice E upon the liquid below.
Demonstration.—Because the orifice F of the tube is covered by the filter (by constr.) which separates the lighter liquid from the heavier, it follows that, if the tube be immersed to the bottom of the vessel, the lighter liquid alone which is mixed with the heavier ought to rise through the filter into the tube, and that, too, higher than the surface of the surrounding liquid (by hyp. 2), so that AC.EF = 2L : G+L; but since by constr. AC : EF > 2L ⋅ G+L it necessarily follows (by hyp. 3) that the lighter liquid will flow over by the orifice E into the vessel below, and there will meet the heavier and be again mixed with it; and it will then penetrate the filter, again ascend the tube, and be a second time driven through the upper orifice. Thus, therefore, will the flow be continued for ever.—Q E D.
Bernoulli then proceeds to apply this theory to explain the perpetual rise of water to the mountains, and its flow in rivers to the sea, which others had falsely attributed to capillary action—his idea being that it was an effect of the different densities of salt and fresh water.
One really is at a loss with Bernoulli's wonderful theory, whether to admire most the conscientious statement of the hypothesis, the prim logic of the demonstration, so carefully cut according to the pattern of the ancients, or the weighty superstructure built on so frail a foundation. Most of our perpetual motions were clearly the result of too little learning; surely this one was the product of too much.
(G. Ch)
PERPETUITY (Lat. perpetuus, continuous), the state of being perpetual or continuing for an indefinite time; in law the tying-up of an estate for a lengthened period, for the purpose of preventing or restricting alienation. As being opposed to the interest of the state and individual effort, the creation of perpetuities has been considerably curtailed, and the rule against perpetuities in the United Kingdom now forbids the making of an executor interest unless beginning within the period of any fixed number of existing lives and an additional period of twenty-one years (with a few months added, if necessary, for the period of gestation). The rule applies to dispositions of personal property (see Accumulation) as well as of real property. There are certain exceptions to the rule, as in the case of limitations in mortmain and to charitable uses, and also in the case of a perpetuity created by act of parliament (e.g. the estate of Blenheim, settled on the duke of Marlborough, and Strathfieldsaye on the duke of Wellington). In the United States the English common-law rule against perpetuities obtains in many of the states; in others it has been replaced or reinforced by statutory rules (see Gray on Alienation, § 42). Charities may be established in perpetuity, and provision may be made for an accumulation of the funds for a reasonable time, e.g. for 100 years (Woodruff v. Marsh, 63 Conn. Rep. 125; 38 Amer. St. Rep. 346). The general tendency of American legislation is to favour tying up estates to a greater extent than was formerly approved.
PERPIGNAN, a town of south-western France, capital of the department of Pyrénées-Orientales, on the right bank of the Têt, 7 m. from the Mediterranean and 42 m. S. by W. of Narbonne by rail. Pop. (1906), town, 32,683; commune, 38,898. The north-west quarter of the town is traversed by the Basse, a tributary of the Têt, while to the south it is overlooked by a citadel enclosing a castle (13th century) of the kings of Majorca. The chapel is remarkable as being a mixture of the Romanesque, Pointed and Moorish styles. The ramparts surrounding the citadel are the work of Louis XI., Charles V. and Vauban. The sculptures and caryatides still to be seen on the gateway of the citadel were placed there by the duke of Alva. The cathedral of St Jean was begun in 1324 and finished in 1509. The most noteworthy feature in the building is an immense reredos of white marble (early 17th century) by Bartholomew Soler of Barcelona.
In the north of the town commanding the gateway of Notre-Dame (1481) there stands a curious machicolated stronghold known as the Castillet (14th and 15th centuries), now used as a prison. The buildings of the old university (18th century) contain the library and the museum, the latter possessing the first photographic proofs executed by Daguerre and a collection of sculptures and paintings. Statues of François Arago, the astronomer, and Hyacinthe Rigoud, the painter, stand in the squares named after them.
Perpignan is a fortiied place of the first class, and seat of a prefect, a bishop and a court of assizes, and has tribunals of first instance and of commerce, a chamber of commerce, a branch of the Bank of France, a communal college for boys, a school of music and training colleges for both sexes. The higher tribunal of Andovic sits at Perpignan. Trade is in wine, iron, wool, oil, corks and leather.
Perpignan dates at least from the 10th century. In the 11th and 12th centuries it was a capital of the counts of Roussillon. from whom it passed in 1172 to the kings of Aragon. Philip the Bold, king of France, died there in 1285, as he was returning from an unsuccessful expedition into Aragon. At that time it belonged to the kingdom of Majorca, and its sovereigns resided there until, in 1344, that small state reverted to the possession of the
