V E N 



placed ereA, and reaching above the ground ; ufually fol- 

 dered to the turns, or elbows, of pipes. The vents of large 

 pipes are to be as high as the fuperficies of the refervoir, 

 unlefs there be a valve in them. 



Vent is alfo ufed for a little hole, pierced in vellels of 

 wine, beer, &c. that are on tap ; and which admits air 

 enough to make the liquor run, but Bot fo much as to cor- 

 rupt and fpoil it. 



Vent, again, is applied to the covers in wind-furnaces, 

 by which the air enters, which ferves them for bellows ; and 

 which are flopped with regifters, or dices, according to the 

 degree of heat required : as in the furnaces of glafs-houfes, 

 affayers, &c. 



Vent is alfo ufed for a pipe of lead, or other matter ; 

 one end of which opens into the cell of a neceflary-houfe, 

 and the other reaches to the roof of the houfe, to give 

 room for the corrupt fetid air to exhale. 



There are alfo vents, or apertures, made in the walls 

 wliich fuftain terraces, to furnilh air, and give a paffage for 

 the waters. 



This kind of vent the Italians, and we from them, call a 

 barhacane. 



Vent, in Gunnery. See TovcH-Hole. 

 The common method of placing the vent is within about 

 a quarter of an inch from the bottom of the chamber or 

 bore. Some, however, have thought, that if the vent was 

 to come out at the middle of the charge, the powder would 

 be inflamed in lefs time than in any other cafe ; but Mr. 

 MuUer, by firing mortars with two vents, one at the bot- 

 tom and the other in the middle, and fo contrived that one 

 was Ihut whilft the other ferved to fire, found always the 

 range of the (hell greater when the lower vent was ufed, 

 than when the powder was fired by the middle one. Artil- 

 lery, p. 83. 



Mr. Thompfon (Count Rumford) has lately made a num- 

 ber of experiments, in order to determine the bed pofition 

 of the vent ; from the refult of which it appears, that the 

 effeft of placing the vent in different pofitions with refpeft 

 to the bottom of the chamber, is different in different 

 charges ; but the difference in the force exerted by the 

 powder, which arofe from the particular pofition of the 

 vent, was in all cafes fo inconfiderable, as to afford occafion 

 for concluding, that any given charge of powder exerts 

 nearly the fame force, whatever is the pofition of the vent. 

 He infers, upon the whole, that in the formation of fire- 

 arms no regaid need be had to any fuppofed advantages that 

 gunfmiths and others have propofed to derive from particu- 

 lar fituations for the vent ; fuch as diminifhing the recoil, 

 increafing the force of the charge, &c. ; but the vent may 

 be indifferently in any part of the chamber where it will beil 

 anfwer upon other accounts ; and he thinks there is little 

 doubt but the fame thing will hold good in great guns, and 

 all kinds of heavy artillery. Workmen in general agree, 

 that the vent in fire-arms lliould be as low or far back as 

 pofTible, in order, as they conceive, to leffen the recoil : 

 accordingly fome make the bottom of the chamber flat, and 

 bring the vent out even with the end of the breech-pin ; 

 others make the vent flanting tlirough the breech-pin, in 

 fueh a manner as to enter the bore juft in its axis ; others 

 again make the bottom of the chamber conical ; and there 

 are thofe who make a little cylindric cavity in the breech- 

 pin, of about two-tenths of an inch in diameter, and near 

 half an inch in length, coinciding with the axis of the bore, 

 and bring out the vent even with the bottom of tliis httle 

 cavity, 



. The objeftion to the firil method is, that the vent is apt 

 to be ftopped up by the foul matter that adheres to the 

 Vot. XXXVI, 



V E N 



piece after firing, and which is apt to accumulate, efpecially 

 m damp weather. The fame inconvenience in a greater 

 degree attends the other methods, with the addition of 

 another, arifing from the increafed length of the vent ; for 

 the vent being longer, is not only more liable to be ob- 

 fl^rufted, but it takes a longer time for the flame to pafs 

 through it into the chamber ; in confequence of which the 

 piece is flower in going off, or, as fportfmen term it, is apt 

 to hang fire. Mr. Thompfon propofes, that the bottom of 

 the bore fliould be in form of a hemifphere ; and that the 

 vent fliould be brought out direftly through the fide of the 

 barrel, in a line perpendicular to its axis, and pointing to 

 the centre of the hemifpheric concavity of the chamber. In 

 this cafe the vent would be the fliorteil poffible ; it would be 

 the leaft hable to be obflruded, and the piece would be 

 more eafily cleaned. Similar advantages, he apprehends, 

 would be gained by making the bottom of the bore and 

 vent of the great guns in the fame manner. Phil. Tranf. 

 vol. Ixxi. pari ii. p. 272, &c. 



From a variety of experiments made by order of the king 

 of PrufTia in 1765 and 1766, it appears, that the concave 

 chamber produced the greatefl ranges, and that the bottom 

 of the chamber is the beil place for the vent. 



VENT-ylJ/ragal, is that part of a gun or howitz which 

 determines the vent-field. 



Vekt-FUU, is the part of a gun or howitz between the 

 breech-mouldings and the aftragal. 



Vent, Port. See Port-vent. 



VENTA, in Ancient Geography, a name given to feveral 

 Britifti towns, of which our antiquaries have given differ- 

 ent etymologies. Mr. Baxter's conjefture may be allowed 

 to be moft probable, who fuppofes that it is derived from 

 ivenJ, or ivent, which fignifies head or chief. For it is ob- 

 fervable, that all the towns which were named Venta, were 

 the capitals or chief towns of the nations or people to whom 

 they belonged. 



Venta Belgarum, a town of Britain, placed in the feventh 

 Iter or route of Antonine, from Regnum or Chichefter to 

 London, between Claufentum or Old Southampton, and 

 Calleva Atrebatilm or Silchefter ; and fituated at the pre- 

 feut Winchelter, as our antiquaries agree. It was the 

 capital of the Belgse. 



Venta Icenorum, a town of Britain, placed at the head of 

 the ninth Iter or route of Antonine, 128 miles from London. 

 This town was probably the capital of the Iceni, or ancient 

 inhabitants of Norfolk, Suffolk, Cambridgefliire, and Hun- 

 tingdonfliire ; and it is generally fuppofed by our anti- 

 quaries to have been fituated at Caifter, upon the river 

 Yare, about three miles from Norwich, which is thought to 

 have arifen out of the ruins of this ancient city. Here have 

 been found fome faint veiliges of this ancient capital of the 

 Iceni. 



Venta Silurum, a Britifh town, placed in the fourteenth 

 Iter or route of Antonine, from Ifca or Caerleon, to Cal- 

 leva or Silchefler. This was a confiderable town of the 

 Silures, between Ifca and Abona. It is our Caergwent. 

 See Silures. 



Venta Cibay, L,a, in Geography, a town of Spain, 

 in Guipufcoa ; 6 miles from Trevigno. 



Venta de Cruz, a fea-port town of America, on the 

 ifthmus of Darien, on the river Chagre, where the merchan- 

 dize from Panama is put on board barks to be conveyed to 

 Porto Bello ; 20 miles N. of Panama. N. lat. 9° 26'. 



Venta Qjiemada, a town of Spain, in the province of 

 Jaen ; 42 miles N. of Jaen. 



Venta de rn Medio, a town of Peru ; jo miles N. of 

 Oruro. 



4 Z Venta 



