6175 



PISTON 



Pistol. Ancient and modern forms of the weapon. 1. Italian dag, or short heavy piece, c. 1650. 2. German doable 

 horse pistol, with 2 sets o! mechanism, 16th century. 3. Double pistol, 16th century. 4. Double pisto! with single trigger 

 actuating 2 hammers. 5. Double grip saddle pistol, with cartridge ejector. 6. Colt's Derringer single-barrelled pistol. 

 7. Colt hammerless automatic pistol with 6-shot magazine. 8. Mauser automatic, showing method of inserting clip of 10 rounds 



Pistol. Comic character in King 

 Henry IV, Part 2, The Merry Wives 

 of Windsor, and King Henry V. 

 In the first of these plays he is 



Pistol declaiming against Fluellen. 

 From an illustration to King 

 , Henry V, iv. 1, by H. C. Selous 



turned out of the Boar's Head by 

 Falstaff for insolence to Doll Tear- 

 Sheet, and subsequently brings 

 him news of Prince Hal's accession 

 to the throne. In the second he is 

 discharged from Falstaff s service 

 for refusing to deliver a love-letter 

 to Mistress Page, and takes his re- 

 venge by mixing as a hobgoblin 

 with the supposed fairies, and pinch- 

 ing Falstatf in Windsor Park. In 

 the third he is married to Mistress 

 Quickly (who dies before the end 

 of the play), and going to the war 



in France is cudgelled by Fluellen, 

 who makes him eat the leek. 



Pistole. French name of an 

 obsolete Spanish gold coin in use 

 from the 16th century. A double 

 escudo, it was worth about 17s. 

 The word was generally applied to 

 similar gold coins, e.g. the Louis d'or. 



Piston. Sliding body moved by 

 or moving against fluid pressure. 

 It usually consists of a short cylin- 

 der fitting within a cylindrical 

 vessel along which it moves to and 

 fro. Pistons used in steam and 

 internal-combustion engines make 

 an easy running fit with the cylin- 

 der, and are provided with elastic 

 rings, fitting in external grooves, 

 which press outwards against the 

 cylinder and prevent leakage past 

 the pistons. Steam-engine pistons 

 are usually exposed to pressure on 

 both sides, in which case they have 

 a length of face from back to front 

 only one-fifth to one-seventh the 

 diameter, being steadied by the 

 piston-rod working through a 

 gland at one end of the cylinder. 



The trunk piston, used in most 

 gas and oil engines for open-ended 

 cylinders, is longer than its dia- 

 meter, so as to be stable under the 

 oblique pressure of the connecting- 

 rod attached directly to it. In force- 

 pumps a solid plunger is often em- 

 ployed instead of a piston. It 

 passes through a water-tight gland 

 and does not touch the walls of the 

 pump barrel. Plungers work with 

 less friction than pistons and leak- 

 age past them is more easily pre- 

 vented when pressures are very 



high. The pistons of high-speed 

 engines should be made as light 

 as is consistent with sufficient 



Pistole. Obverse and reverse of 

 Spanish gold coin. Actual diameter, 



1* in. 



strength. See Hydraulics; Inter- 

 nal Combustion Engine ; Motor 

 Car; Motor Cycle; Pump. 



Piston. In music, a valve ap- 

 plied to wind instruments for the 

 purpose of obtaining a complete 

 chromatic scale. The series of 

 sounds producible by any tube has, 

 in accordance with acoustical laws, 

 many gaps in it, especially in the 

 lower part of the compass, and in- 

 ventors from quite early times 

 have endeavoured to overcome 

 this drawback. The solution was 

 found in valves, which, by increas- 

 ing the length of the tube, supplied 

 other series as desired. The first 

 valve lowers the pitch a tone, the 

 second a semi-tone, the third three 

 semi-tones, and the fourth five 

 semi-tones. When two or more 

 valves are depressed simultaneously 

 the further changes of pitch can be 

 effected. Thus any note can be 

 obtained, and modulating passages 

 are rendered practicable. The in- 

 struments to which pistons are 

 applied are horns, trumpets, cor- 

 nets, and the different varieties of 



