PULASKI 



PULLEY 



487 



Plllaski, CASIMIR, a Polish count who fell in 

 the American revolution, was born in Podolia, 4th 

 March 1748, took an active part in the war against 

 Russia, and lost his estates and was outlawed at 

 the partition of Poland in 1772. In 1777 he went 

 to America, and for his conduct at the Brandywine 

 was given a brigade of cavalry, which he com- 

 manded until March 1778. He then organised 

 'Pulaski's legion,' a corps of lancers and light 

 infantry, in which he enlisted even prisoners of war 

 and deserters. In May 1779 he entered Charleston, 

 and held it until the place was relieved ; a furious 

 assault which he had made on the British was 

 repelled, but he afterwards followed and harassed 

 them until they left South Carolina. At the siege 

 of Savannah on tjie 9th of October he fell in the 

 assault at the head of the cavalry, and died on 

 board the brig Wasp two days later. In 1824 

 Lafayette laid the corner-stone of a monument to 

 Pulaski, in Savannah, which was completed in 

 1855. 



Pnlci, LuiOI, an Italian poet, born at Florence, 

 3d December 1432, and died in 1484 (or 1487), was 

 an intimate friend of Lorenzo de' Medici and of 

 Politian. He is the author of a celebrated poem, 

 // Morgante Maggiore ( ' Morgante the Giant'), a 

 burlesque epic of which Roland is the hero. This 

 poem is one of the most valuable sources for the early 

 Tuscan dialect, the niceties and idioms of which 

 have been employed by Pulci with great skill (see 

 ITALY, Vol. VI. p. 254 ). The first edition appeared 

 at Venice in 1481, and the book has since been fre- 

 quently reprinted. Pulci wrote further a humorous 

 novel (printed in Classici Italiani, Milan, 1804) 

 and several humorous sonnets. His brother BER- 

 NARDO (born circa 1430) wrote an elegy on the 

 death of Simonetta, mistress of Julian de' Medici, 

 and the first translation of the Eclogues of Virgil. 

 LUCA, another brother (Ixirn 1431), wrote a poem 

 in honour of Lorenzo de' Medici's success in a 

 tournament ; // Cirijfo Calraneo, a metrical romance 

 of chivalry ; Driadeo cCAmore, a pastoral poem ; 

 and Epistole Eroiche. 



Pnlex. See FLEA. 



I'ulirat. a town of British India, 20 miles N. 

 of Madras, the first settlement of the Dutch in 

 India ; pop. 4967. It stands on an island in a large 

 inlet of the sea called the Lake of Pulicat. 



Pnlko'wa, a village of Russia, 10 miles S. of 

 the site of a magnificent observatory (59 46' 18" 

 N. lat. and 30 19' 4tf' E. long.), the 'St Peters- 

 burg observatory,' built by the Czar Nicholas in 

 1838-39. In 1882 one of the largest telescopes in 

 the world was erected here. 



Pulley, one of the mechanical powers, consists 

 of a wheel, with a groove cut all round its circum- 

 ference, 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 by the 

 sides of this block the extremi- 

 ties of the axle of the sheave 

 are supported ; the cord which 

 passes over the circumference of 

 the sheave is called the tm-l-li'. 

 Pulleys may be used either singly 

 or in combination ; in the former 

 case they are either fixed or 



Pig. 1. 



movable. The fixed pulley ( fig. 1 ) gives no mechani- 

 cal advantage ; it merely changes the direction in 

 which a force would naturally be applied to one 

 more convenient : thus, W can be raised without 

 lifting it directly by merely pulling P down. The 

 tingle movable pulley, with parallel cords, gives a 

 mechanical advantage = 2 (fig. 2); for a little 



Fig. 2. 



consideration will show that, as the weight, W, is 

 supported by two strings, the stress on each string 

 is JW, and the stress on the one being supported 

 by the hook, A, the power, P, requires merely to 

 support the stress on the other 

 string, which passes round C. 

 The fixed pulley, C, is only of 

 service in changing the naturally 

 upward direction of the power 

 into a downward one. If the 

 strings in the single movable 

 pulley are not parallel there is a 

 diminution of mechanical advan- 

 tage i.e. P must be more than 

 half of W to produce an exact 

 counterpoise ; if the angle made 

 by the strings AB and BC is 120, 

 P must be equal to W ; and if 

 the angle be greater than this 

 there is a mechanical disadvantage, or P must be 

 greater than W. The following are examples of 

 different combinations of pulleys, generally known 

 as the first, second, and third 'systems of pulleys. 

 In the first system one end of each cord is fastened 

 to a fixed support above ; each cord descends, 

 passes round a pulley ( to the lowest of which the 

 weight, W, is fastened), and is fastened to 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 mov- 

 able pulley is supported on both sides by a string 

 having a tension, P, the tension applied in its sup- 

 port is 2P. The tension of the string marked (2) 



Fig. 4. 



Fig. 5. 



is therefore 2P, and the second movable pulley is 

 supported by a force equal to 4P. It may similarly 

 l>e shown that the force applied by the string! 

 marked (4) in support of the last pulley (which 

 is attached to W) is 8P. Hence we see that, 

 according to this arrangement, 1 IK can support 

 4 IK if two movable pulleys are used ; 8 Ib. if 

 there are three movable pulleys; 16 Ib. if there 

 are four movable pulleys ; and if there are n mov- 

 able pulleys 1 Ib. can support 2" Ib. It must be 

 noticed, however, that in practice the weight of 

 the cords, and of the pulleys, and the friction of 

 the cord on the pulleys must be allowed for ; and 

 the fact that in this system all of these resist the 

 lotion of the power, P, and that to a large extent, 

 has rendered it of little use in practice. The 

 second system is much inferior in producing a 

 mechanical advantage, but it is found to be much 



