PULEX-PULLEY. P. are a series of sonnets (often grossly indecent), the block of the next pulley, with the exception of La Beca du Dicomano (a parody of a pastoral poem the last cord, which passes round a fixed pulley by Lorenzo de' Medici); Confessione a la San Ver- above, and is attached to the counterpoise P. The gine, a novel; and some letters.-BERNARDO PULCI, tension of a string being the same in all its parts, elder brother of Luigi, wrote an elegy on the death the tension of every part of the string marked (1) of Simonetta, mistress of Julian de' Medici; and a in fig. 3 is that which is poem on the passion of Christ, and also executed produced by the weight of P, the first translation of the Eclogues of Virgil.-consequently, as the last movLUCA PULCI, another brother, achieved some literary able pulley is supported on reputation too by his Giostra di Lorenzo de' Medici, both sides by a string hava poem in honour of the success won by Lorenzo in a tournament; Il Ciriffo Calvaneo, a metrical romance of chivalry; Driadeo d'Ancore, a pastoral poem; and Epistole Eroide. PU'LEX. See FLEA. PULKO VA, a village of Russia, in the government of St Petersburg, about 9 miles south of the capital, contains a population of 600. It stands on a ridge called the Pulkova Hills, which command a splendid view of St Petersburg, and is noted for its magnificent observatory, built by the Czar Nicholas, and placed under the direction of M. Otto Struve. For an interesting description of the observatory, see Professor C. Piazzi Smyth's Three Cities in Russia (2 vols., Lond. 1862). PO w = 2 Fig. 3. W ing a tension P, the tension Fig. 4. PULLEY, one of the Mechanical Powers (q. v.), consists of a wheel, with a groove cut all round its circumference, and movable on an axis; the wheel, which is commonly called a sheave, is often placed inside a hollow oblong mass of wood called a block, and to the sides of this block the extremities of the sheave's axle are fixed for support; the cord which passes over the circumference of the sheave is called the tackle. Pulleys may-The second system is much inbe used either singly or in com- ferior in producing a mechanical bination; in the former case, advantage, but it is found to be they are either fixed or movable. much more convenient in practice, The fixed pulley (fig. 1) gives no and is modified according to the mechanical advantage; it merely purpose for which it is to be used; changes the direction in which a two prevalent forms are given in force would naturally be applied figs. 4 and 5. In this system, one Fig. 1. to one more convenient-thus, string passes round all the pulleys, W can be raised without lifting and as the tension in every part w it directly by merely pulling P down. The single of it is that produced by the weight movable pulley, with parallel cords, gives a of P, the whole force applied to mechanical advantage: 2 (fig. 2), for a little con- elevate the lower block with its sideration will shew that as the weight, W, is attached weight, W, is the weight P multiplied supported by two strings, the by the number of strings attached to the lower strain on each string is &W, and block; in fig. 4, W = 4P, and in fig. 5, W = 6P, the strain on the one being sup- the pulleys in the upper block ported by the hook A, the being only of use in changing the power, P, requires merely to direction of the pulling force. This support the strain on the other system is the one in common use string, which passes round C. in architecture, in dockyards, and The fixed pulley, C, is only of on board ship, and various modiservice in changing the natu- fications of it-such as White's rally upward direction of the pulley, Smeaton's pulley, &c., have power into a downward one. been introduced; but the simpler If the strings in the single mov- forms shewn above have been able pulley are not parallel, found to answer best.-The third Fig 2 there is a diminution of mecha- system (fig. 6) is merely the first nical advantage-i. e., P must be system inverted, and it is a little more than half of W to produce an exact coun- more powerful, besides having the terpoise; if the angle made by the strings is 120°, weight of the pulleys to support Pmust be equal to W; and if the angle be greater the power, instead of acting in than this, there is a mechanical disadvantage, or opposition to it, as in the former P must be greater than W. The following are case. By this time, it will have Examples of different combinations of pulleys, gener- been evident to the reader that ally known as the first, second, and third systems the mechanical advantage is not of palleys. In the first system, one end of each cord produced by the pulleys, but by the strings, and is fastened to a fixed support above; each cord that the pulleys are merely useful in keeping the descends, passes round a pulley (to the lowest of strings in a certain position, changing with as little Fig. 5. PULMONATA-PULSE affording a convenient means of attaching the subjects. The pulpit (in Arabic, mimber forms weight. Theoretically, the larger the number of α 1 PÅ કન્ન a W Fig. 6. movable pulleys in one combination, the greater is the mechanical advantage afforded; but the enormous friction produced, and the want of perfect flexibility in the ropes, prevent any great increase in the number of pulleys. PULMONA'TA, an order of gasteropodous molluscs, having, for the purpose of respiration, a vascular air-sac or lung, which opens by a hole under the margin of the mantle, capable of being contracted or dilated at pleasure. Some are terrestrial, some aquatic. Slugs and snails are familiar examples of the former; water-snails, or pondsnails (Limnæa, Planorbis, &c.), of the latter. Most of the P. are protected by a shell; in some, as slugs, the shell is internal and rudimental. PULNEYS, a range of hills in the Madura district of the Madras Presidency of India. The average height of this range is about 7500 feet above the level of the sea. It possesses peculiar advantages for the establishment of a sanitarium. The climate is one of the most equable anywhere to be found, the variation of the thermometer during twelve months in a (From Parker's Glossary.) closed room without a fire being observed to be Pulpit (Fotheringhay, Northamptonshire, 1440 a. D.). no greater than between 58° and 62°. At present, there are only a few European residences built on these hills. PULO-PENANG. See PRINCE OF WALES' ISLAND. PULP, a term employed to describe those very soft and succulent parts of plants, almost exclusively of fruits, which consist of cellular tissue with much juice. The pulp of a fruit is sometimes found in one part of it, sometimes in another; thus, in the peach, plum, and other drupes, it is the mesocarp; in the grape and gooseberry, it is developed from the placentas, and the seeds are embedded in it. PULPIT (Lat. pulpitum), an elevated tribune or desk, from which sermons, lectures, and other solemn religious addresses are delivered. In great churches, the pulpit is commonly placed against the wall, or in juxtaposition with a pillar or buttress. Originally it would appear to have been used chiefly for the singing, chanting, or recitation which form part of the public service, and was a kind of stage sufficiently large to accommodate two or even more chanters. For the convenience of the hearers, this stage began to be used by the bishop, priest, or deacon, for the delivery of the homily; and thus by degrees a tribune expressly suited to the latter use alone came to be introduced. In some of the older churches, the ambo or pulpitum is still used for the chanting of the Gospel and Epistles. In Catholic churches, the pulpit is generally distinguished by some religious emblems, especially by the crucifix; and the pulpits of the Low Countries and of Germany are often masterpieces of wood-carving, the preaching-place in some of them forming part of a great artistic group, as of the Conversion of St Paul, the Vocation of Peter and Andrew, the one of the scanty appliances of Mohammedan worship. PULQUE, a favourite beverage of the Mexicans and of the inhabitants of Central America, and some parts of South America; made from the juice of different species of Agave (q. v.), which is collected by cutting out the flowering-stem from the midst of the leaves in the beginning of its growth, and scooping a hole for the juice. From this cavity, large quantities of juice are removed daily for months. The juice is an agreeable drink when fresh, but is more generally used after fermentation, when it has a very pleasant taste, but a putrid smell, disgusting to those unaccustomed to it. Pulque is retailed in Mexico in open sheds called Pulquerias, which also serve for dancing-rooms. When mixed with water and sugar, and allowed to ferment for a few hours, it forms a beverage called Tepache. A kind of spirit is also prepared from it. PULSE (Lat. puls), a name for the edible seeds of leguminous plants, as corn is the name for the edible seeds of grasses. Peas and beans are the most common and important of all kinds of pulse; next to them may be ranked kidney-beans, lentils, chickpeas, pigeon-peas, &c. Legumine (q. v.), a very nitrogenous principle, abounds in all kinds of pulse. Legumine forms a thick coagulum with salts of lime, wherefore all kinds of pulse remain hard if boiled in spring-water containing lime. The best kinds of pulse are very nutritious, but not easy of digestion, and very apt to produce flatulence. PULSE (Lat. pulsus, a pushing or beating). The phenomenon known as the arterial pulse or arterial pulsation is due to the distention of the arteries consequent upon the intermittent injection of blood into their trunks, and the subsequent contraction which PULTOWA-PULU. importance of ascertaining the various meanings of this symptom. pero ptible to the touch in all excepting very minute arteries, and in exposed positions, is visible to the eye. This pulsation,' says Dr Carpenter, involves an The pulse is said to be full when the volume of augmentation of the capacity of that portion of the the pulsation is greater than usual, and it is called artery in which it is observed; and it would seem small or contracted under the opposite condition. to the touch as if this were chiefly effected by an A full pulse may depend upon general plethora, on increase of diameter. It seems fully proved, how- a prolonged and forcible contraction of the left venever, that the increased capacity is chiefly given by tricle of the heart, and possibly, to a certain extent, the elongation of the artery, which is lifted from on relaxation of the arterial coats; while a small its bed at each pulsation, and when previously pulse results from general deficiency of blood, straight, becomes curved; the impression made upon from feeble action of the heart, from congestion of the finger by such displacement not being distin- the venous system, or from exposure to the action guishable from that which would result from the of cold. When very small, it is termed thread-like. dilatation of the tube in diameter. A very obvious The tension of the pulse is the property by which example of this upheaval is seen in the prominent it resists compression, and may be regarded as temporal artery of an old person.'-Principles of synonymous with hardness. A hard pulse can Human Physiology, 4th ed., p. 492. The number of scarcely be stopped by any degree of pressure of pulsations is usually counted at the radial artery the finger. It occurs in many forms of inflammaat the wrist, the advantages of that position being tion, and its presence is commonly regarded as one that the artery is very superficial at that spot, and of the best indications of the necessity of venethat it is easily compressed against the bone. In section. A soft or compressible pulse is indicative some cases, it is preferable to count the number of of general weakness. contractions of the heart itself. The qualities which are chiefly attended to in the pulse are its frequency, its regularity, its fulness, its tension, and its force. The frequency of the pulse varies greatly with the age. In the foetus in utero, the pulsations vary from 140 to 150 in the minute; in the newly-born infant, from 130 to 140; in the 2d year, from 100 to 115; from the 7th to the 14th year, from 80 to 90; from the 14th to the 21st year, from 75 to 85; and from the 21st to the 60th year, 70 to 75. After this period, the pulse is generally supposed to fall in frequency, but the most opposite assertions have been made on this subject. There are many exceptions to the preceding statement; young persons being often met with having a pulse below 60, and cases not unfrequently occurring in which the pulse habitually reached 100, or did not exceed 40 in the minute, without apparent disease. The numbers which have been given are taken from an equal number of males and females, and the pulsations taken in the sitting position. The influence of sex is very considerable, especially in adult age, the pulse of the adult female exceeding in frequency that of the male of the same age by from 10 to 14 beats in the minute. The effect of muscular exertion in raising the pulse is well known; and it has been found by Dr Guy that posture materially influences the number of pulsations. Thus, in healthy males of the mean age of 27 years, the average frequency of the pulse was, when standing, 81, when sitting, 71, and when lying, 66, per minute; while in healthy females of the same age the averages werestanding, 91; sitting, 84; and lying, 79. During Exp, the pulse is usually considerably slower than in the waking state. In disease (acute hydrocephalus, for example), the pulse may reach 150 or EVED 200 beats; or, on the other hand (as in plexy and in certain organic affections of the heart), it may be as slow as between 30 and 20. Irregularity of the pulse is another condition requiring notice. There are two varieties of irreguiar palse: in one, the motions of the artery are equal in number and force, a few beats being from time to time more rapid and feeble than the rest; in the other variety, a pulsation is from time to time entirely left out, constituting intermission of the pulse. These varieties often concur in the same person, but they may exist independently of each other. Irregularity of the pulse is natural towme persons; in others, it is the mere result d debility; but it may be caused by the most Ervas disorders, as by disease of the brain, or by ergic disease of the heart; and hence the practical The strength of the pulse depends chiefly on the force with which the blood is driven from the heart, but partly also upon the tonicity of the artery itself and the volume of the blood. A strong pulse is correctly regarded as a sign of a vigorous state of the system; it may, however, arise from hypertrophy of the left ventricle of the heart, and remain as a persistent symptom even when the general powers are failing. As strength of the pulse usually indicates vigour, so weakness of the pulse indicates debility. There may, however, be cases in which weakness of the pulse may occur in association with undiminished energy of the system at large. For example, active congestion of the lungs may so far impede the passage of the blood through these organs that it cannot reach the heart in due quantity; the necessary result is a weak and feeble pulse, which will rapidly increase in strength if the congestion is relieved by free blood-lettings. Various expressive adjectives have been attached to special conditions of the pulse, intc the consideration of which our space will not permit us to enter. Thus, we read of the jerking pulse, the hobbling pulse, the corded pulse, the wiry pulse, the thrilling pulse, the rebounding pulse, &c. PULTOWA. See POLTAVA. PU'LTUSK, a town of Poland, in the govern. ment of Plock, is situated in a thickly-wooded district on the Narew, 35 miles north-north-east of Warsaw. It contains numerous churches and a very large bishop's palace. Pop. 4772. Here, on December 26, 1806, was fought one of the battles of the campaign of Eylau, between the Russians The field was most obstinately and the French. contested, but the victory, which, however, was claimed by both armies, inclined in favour of the French. PU'LU, a beautiful substance, resembling fine silk, of a rich brown cclour and satin lustre, used largely as a styptic by the medical practitioners of Holland, and lately introduced into this country for the same purpose. It consists of the fine hairs from the stipes of one or more species of tree-fern, referrible, without doubt, to the genus Cibotium. It was first imported into this country in 1844 from Owhyhee under the name of Pulu, or vege table silk, and was proposed as a substitute for silk in the manufacture of hats, but could not be applied. In 1856, it was again imported from Singapore under the Malay names of Penghawar Djambi and Pakoe Kidang, and was said to have been used in Dutch pharmacy for a long period as a styptic. Several importations have since taken PUMA-PUMPS. place, and it has been successfully used. It acts mechanically by its great absorbent powers. PU'MA, or COUGAR (Felis concolor, Leopardus concolor, or Puma concolor), one of the largest of the American Felida, rivalled only by the jaguar. It is sometimes called the American Lion, although it is more allied to the leopard, notwithstanding its want of spots and stripes. It is from 4 to 4 feet in length from the nose to the root of the tail, and the tail about 2 feet or 24. The fur is thick and close, reddish-brown above, lighter on the sides, and reddish-white on the belly; the muzzle, chin, throat, and insides of the legs grayish-white, the breast almost pure white. Young pumas have darkbrown spots in three rows on the back, and scattered markings elsewhere, exhibiting the relation to the leopards. The long tail of the P. is covered with thick fur, and is generally coiled up, as if it were prehensile, which it does not seem to be, although the P. climbs trees very well, and often descends on its prey from among their branches. The P. was formerly found in all except the coldest parts of America, but is now rare in most parts of North America, having been expelled by man. It rarely attacks man, but is very ready to prey on domestic animals, and seems to have a thirst for blood beyond that of other Felida, one P. having been known to kill 50 sheep in a night, drinking a little of the blood of each; a very sufficient reason for the anxiety which all American farmers shew for its destruction. Yet it is easily tamed, and when tamed, a very gentle creature, purring like a cat, and shewing equal love of attentions. The geographical range of the P. extends far southwards in Patagonia, and northwards even to the state of New York, although it is now very rare in all long-settled parts of North America. the Painter (Panther) of North American farmers. It sometimes issues from the forests, and roams over prairies and pampas, and is not unfrequently caught by the lasso of South American hunters.A BLACK P. (Felis nigra of some naturalists), a doubtful species, and probably only a variety of the common P., is found in some parts of South America. It is action. Of these, as the most important, we shall describe in detail the following: 1. The Lift or Suction Pump; 2. The Lift and Force Pump; 3 The Chain-pump; 4 The Centrifugal Pump; 5 The Jet-pump. 1. The Lift or Suction Pump.-The diagrams figs. 1 and 2 represent the ordinary suction pump. A is a cylinder, which is called the barrel; with it is connected at the bottom a pipe, B, which communicates with the water to be raised; and at its top is another pipe, C, which receives the water raised. In the barrel are placed two valves, D and E. Dis fixed in position at the bottom of the barrel; E is Fig. 1. H attached to, and forms part of the piston F, which moves up and down the barrel when motive-power is applied to the rod G. The piston, or bucket, consists of a cylindrical piece of wood or metal, which fits exactly the barrel in which it moves, so that no water or air can pass between its circum ference and the sides of the cylinder. This tight fitting is attained in wooden pistons by surrounding them with a leather ring; and in those of metal, by hemp or other packing, which is wrapped round PU'MICE, a mineral found in volcanic countries, generally with obsidian and porphyries. In chemical composition, it agrees with obsidian, of which it may be regarded as a peculiar form, rapidly cooled from a melted and boiling state. It is of a white or gray colour, more rarely yellow, brown, or black; and so vesicular, that in mass, it is lighter than water, and swims in it. The vesicles, or cells, are often of a much elongated shape. P. often exhibits more or less of a filamentous structure; and it is said to be most filamentous when silica is most abundant in its composition. It is very hard and very brittle. It is much used for polishing wood, ivory, metals, glass, slates, groove made in their outer surface. The hollow interior of the piston is closed at the top by the marble, lithographic stones, &c., and in the pre-valve E, which is a kind of door opening on a hinge, paration of vellum, parchment, and some kinds of leather. Among other purposes to which it is applied is the rubbing away of corns and callosities. Great quantities are exported from the Lipari Isles to Britain and all parts of Europe. The Lipari Isles are in great part composed of P., which there, as in some other places, occurs as a rock. P. is the chief product of some volcanic eruptions; but in some eruptions, none is produced. It is found also in regions where there are now no active volcanoes, 38 at Andernach on the Rhine. PUMPKIN. See GOURD. PUMPS are machines for raising water and other fluids to a higher level. They are divided at one side of it, in an upward direction, on the application of pressure, and shutting on to its seat on the piston when the pressure is removed. When opened, water or air can pass through it to the upper side of the piston; but when shut, none can pass from one side of the piston to the other. The other valve, D, is similar to it in all respects, except that, as before stated, it is fixed in the bottom of the barrel; it also can only open upwards. On To describe the action of the pump, we shall suppose the piston to be at the bottom of the barrel, and the pump to contain nothing but air. moving the piston up the barrel-the valve in it being shut, and kept so by the atmospheric pressure E PUMPS. 2. The Lift and Force Pump.-Figs. 3 and 4 represent two varieties of this pump. That shewn in fig. 3 is very similar to the suction-pump before described, with this exception, that the valve E, B part of the barrel from which it is moving; the air relation between the power expended and the work contained in which becoming rarefied, by having to produced, as measured by the water raised-we occupy a greater space, exerts less pressure on the may remark, that the power is expended-1st, in valve D at the bottom of the barrel than the air in raising the water through the required height; 2d, suction-pipe B below it. This valve is thus opened, in overcoming the friction of the moving parts and the air from the suction-of the pump; 3d, in the friction and fluid resistance pipe enters the barrel; so of the water in passing through the valves and pipes; that when the piston has 4th, in the losses arising from the want of proper arrived at the top, a volume proportion between the various parts of the pump. of air equal to the contents The losses arising from these last sources are very of the barrel has passed great, and vary so much according to the confrom the suction-pipe into struction of each particular pump, that no useful the barrel. When the piston estimate can be formed of the efficiency. We may descends, it compresses the say, however, that a pump of this description, to air in the barrel, which shuts yield 50 per cent. of the applied power, must be the valve D; and when the well proportioned and carefully constructed. Cdensity of the compressed air becomes greater than that of the atmosphere, the valve E in the piston is forced open, and the air in the barrel passes to the upper side of the piston. The next upward stroke of the piston again draws a like quantity of air from the suction-pipe into the barrel; and, as none of this air again enters the pipe, but is passed to the upper side of the piston by its downward stroke, the suction-pipe is by degrees emptied of the air it contained. During this process, however, motion has taken place in the water at the foot of the suction-pipe. The surface of the water at His pressed upon by the weight of the atmosphere with a pressure of about 15 lbs. on every square inch; and by the laws of fluidpressure, if an equal pressure is not exerted on the surface of the water in the suction-pipe, the water will rise in it, until the pressure on its surface, plus the weight of its fluid column, balances the pressure of the atmosphere on the surface H outside; so that, as the air in the suction-pipe is rarefied, the water rises in it, until, when all the air is extracted from it, the water stands at the level of the valve D. By the next upward stroke of the piston, the barrel being emptied of air, the water follows the piston, and fills the barrel as it filled the suction-pipe. The pressure produced by the downward stroke shuts the valve D, and forces the water in the barrel through the valve E. The succeeding upward stroke carries this water into the pipe above, and again fills the barrel from the suction-pipe. In like manner, every successive upward stroke discharges & body of water equal to the content of the barrel into the pipe above it, and the pump will draw water as long as the action of the piston is continned. B Fig. 2 The action of this pump may be more shortly described by saying that the piston withdraws the air from the barrel, and produces a vacuum, into which the water rushes through the suction-pipe, pelled by the pressure of the atmosphere on its Surizce This atmospheric pressure balances a column of water of about 33 feet in height; so that the barrel be placed at a greater height than this from the surface of the water in the well, the water vill not rise into it, and the pump will not draw. With regard to its efficiency-that is to say, the 44 Fig. 3. Fig. 4. instead of being fixed on the piston, is placed in the discharge-pipe, the piston itself being solid. The water is drawn up into the barrel by suction in the manner just described in the suction-pipe, and then the pressure of the piston in its downward-stroke forces it through the valve E to any height that may be required. That shewn in fig. 4 is provided with a different description of piston, called the plunger-pole. Its action is precisely the same as that of the other, with this exception, that the plunger-pole, instead of emptying the barrel at every stroke, merely drives out that quantity which it displaces by its volume. It is simply a solid rod of metal, A, moving through a water-tight stuffingbox, B. This stuffing-box is made by placing, on a circular flange of metal, rings of india-rubber or other packing, the inner diameter of which is slightly less than that of the plunger-pole. On these is placed a ring of metal, and through the whole are passed bolts, which, on being screwed tight, force the packing tightly against the plungerpole. It possesses many advantages, for the packing can be tightened and repaired without removal of the piston or stoppage of the pump; also, the cylinder is not worn by its action, nor does it require to be accurately bored out, as in the other form of pump. In these pumps, it will be observed that the water is forced into the ascending pipe or column only on the downward stroke; it will thus be |