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PULEX-PULLEY.

P. are a series of sonnets (often grossly indecent), La Beca du Dicomano (a parody of a pastoral poem by Lorenzo de' Medici); Confessione à la San Vergine, a novel; and some letters.--BERNARDO PULCI, elder brother of Luigi, wrote an elegy on the death of Simonetta, mistress of Julian de' Medici; and a poem on the passion of Christ, and also executed the first translation of the Eclogues of Virgil.LUCA PULCI, another brother, achieved some literary reputation too by his Giostra di Lorenzo de' Medici, a 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 place 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).

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Fig. 3.

the block of the next pulley, with the exception of the last cord, which passes round a fixed pulley above, and is attached to the counterpoise P. The tension of a string being the same in all its parts, the tension of every part of the string marked (1) in fig. 3 is that which is produced by the weight of P, consequently, as the last movable pulley is supported on both sides by a string having a tension P, the tension applied in its support is 2P. The tension of the string marked (2) is therefore 2P, and the second movable pulley is supported by a force equal to 4P. It may similarly be shewn that the force applied by the strings marked (4) in support of the last pulley (which is attached to W), is 8P. Hence we see, that according to this arrangement, 1 lb. can support 4 lbs., if two movable pulleys are used; 8 lbs., if there are 3 movable pulleys; 16 lbs., if there are 4 movable pulleys; and if there are n movable pulleys, 1 lb. can support 2" lbs. It PU'LLEY, one of the Mechanical Powers (q. v.), must be noticed, hewever, that consists of a wheel, with a groove cut all round its in practice, the weight of the circumference, and movable on an axis; the wheel, cords, and of the pulleys, and the which is commonly called a sheave, is often placed friction of the cord on the pulleys, inside a hollow oblong mass of wood called a block, must be allowed for; and the fact, and to the sides of this block the extremities of the that in this system all of these sheave's axle are fixed for sup- resist the action of the power P, port; the cord which passes over and that to a large extent, has the circumference of the sheave rendered it of little use in practice. 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 to one more convenient-thus, string passes round all the pulleys, W can be raised without lifting and as the tension in every part 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 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 P must 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 pulleys. 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, asses round a pulley (to the lowest of strings in a certain position, changing with as little which the weight, W, is fastened), and is fastened to friction as possible the direction of the pull, and

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Fig. 1.

Fig. 2.

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Fig. 5.

PULMONATA—PULSE.

affording a convenient means of attaching the subjects. weight. Theoretically, the larger the number of

Fig. 6.

movable pulleys in one combin-
ation, the greater is the mecha-
nical advantage afforded; but
the enormous friction produced,
and the want of perfect flexi-
bility 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 mar-
gin 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 pond-
snails (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 sanitarium. The climate is one of the most equable anywhere to be found, the variation of the thermometer during twelve months in a

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The pulpit (in Arabic, mimber) forms

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(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.

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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 Temptation of Adam and Eve, and other similar

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, chickLegumine (q. v.), a very peas, pigeon-peas, &c. 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 results from the elasticity of their walls. It is

PULTOWA-PULU.

perceptible 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 augmentation of the capacity of that portion of the artery in which it is observed; and it would seem to the touch as if this were chiefly effected by an increase of diameter. It seems fully proved, however, that the increased capacity is chiefly given by the elongation of the artery, which is lifted from its bed at each pulsation, and when previously straight, becomes curved; the impression made upon the finger by such displacement not being distinguishable from that which would result from the dilatation of the tube in diameter. A A very obvious example of this upheaval is seen in the prominent temporal artery of an old person.'-Principles of Human Physiology, 4th ed., p. 492. The number of pulsations is usually counted at the radial artery at the wrist, the advantages of that position being that the artery is very superficial at that spot, and that it is easily compressed against the bone. In some cases, it is preferable to count the number of 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 were standing, 91; sitting, 84; and lying, 79. During sleep, the pulse is usually considerably slower than in the waking state. In disease (acute hydrocephalus, for example), the pulse may reach 150 or even 200 beats; or, on the other hand (as in apoplexy 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 irregular pulse: in one, the motions of the artery are unequal 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 to some persons; in others, it is the mere result of debility; but it may be caused by the most serious disorders, as by disease of the brain, or by organic disease of the heart; and hence the practical

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importance of ascertaining the various meanings of this symptom.

The pulse is said to be full when the volume of the pulsation is greater than usual, and it is called small or contracted under the opposite condition. A full pulse may depend upon general plethora, on a prolonged and forcible contraction of the left ventricle of the heart, and possibly, to a certain extent, on relaxation of the arterial coats; while a smalĺ pulse results from general deficiency of blood, from feeble action of the heart, from congestion of the venous system, or from exposure to the action of cold. When very small, it is termed thread-like. The tension of the pulse is the property by which it resists compression, and may be regarded as synonymous with hardness. A hard pulse can scarcely be stopped by any degree of pressure of the finger. It occurs in many forms of inflammation, and its presence is commonly regarded as one of the best indications of the necessity of venesection. A soft or compressible pulse is indicative of general weakness.

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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, into 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 colour 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 vegetable 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 Djainbi 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

7

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 Felidæ, 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

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, marble, lithographic stones, &c., and in the preparation 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, as at Andernach on the Rhine.

PUMPKIN. See GOURD.

PUMPS are machines for raising water and other fluids to a higher level. They are divided into several classes according to their mode of

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

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The hollow

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. consists of a cylindrical piece of wood or metal, The piston, or bucket, which fits exactly the barrel in which it moves, so that no water or air can pass between its circumference 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 a made in their outer surface. groove interior of the piston is closed at the top by the valve E, which is a kind of door opening on a hinge, at one side of it, in an upward direction, on the application of pressure, and shutting on to its seat opened, water or air can pass through it to the on the piston when the pressure is removed. When 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.

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. On moving the piston up the barrel-the valve in it being shut, and kept so by the atmospheric pressure above it-no air can pass from above it into the

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