BAL 



BAL 



shape ; its length is about eighteen or 

 twenty inches, sometimes as much as two 

 feet ; colour pale violet ; skin strongly 

 marked into lozenge-shaped reticulations; 

 first dorsal fin three-rayed ; the first very 

 strong; ventral spines rough, and but 

 slightly projecting ; tail somewhat con- 

 vex in the middle of the outline, with 

 falcated tops ; whole body dorsal, and 

 anal fin marked with numerous round 

 blue spots. Native of the Indian and 

 American seas. B. undulatus, or black 

 file-fish, is a native of the Indian seas, ob- 

 served first about the shores of Sumatra 

 by the enterprizing and highly merito- 

 rious traveller Mungo Park. From the 

 mouth to the base of the pectoral fins 

 run three red lines, and the body is ob- 

 liquely undulated by twelve lines of the 

 same colour. Some fish of this genus are 

 called Trigger-fish, from the circum- 

 stance of the firstray of the dorsal fin be- 

 ing fixed by the second, when elevated to 

 a perpendicular position, like the trigger 

 of a gun; this ray cannot be restored to 

 its oblique position without first inclining 

 the second ray, which by a peculiar me- 

 chanism, acts as a prop. See Plate H. 

 Pisces, fig. I. 



BALL, in the military art, compre- 

 hends all sorts of bullets for fire-arms, 

 from the cannon to the pistol. 



Cannon-balls are made of iron ; mus- 

 ket-balls, pistol-balls, &c. are of lead. 

 The experiment has been tried of iron 

 balls for pistols and fusees, but they are 

 justly rejected, not only on account of 

 their lightness, which prevents them 

 from flying straight, but because they 

 are apt to furrow the barrel of the pistol, 

 &c. 



Cannon-balls are always distinguished 

 by their respective calibres : thus, 



For a 



BALL and socket is an instrument made 

 of brass, with a perpetual screw, so as to 

 move horizontally, vertically, and ob- 

 liquely ; and is generally used for the 

 managing of surveying instruments, and 

 astronomical instruments. 



BALLAD, in music, formerly a little 

 history told in verse, and sung to the harp 



or viol, either by the author himself, or 

 the jongleur, whose profession it was to 

 follow the bard and sing his works. 

 About a century since the word ballad 

 began to imply a brief, simple, tale, con- 

 veyed in three or four verses, set to a 

 short and familiar air, in which sense it 

 is now understood. 



BALLANCE, or BALANCE, in mecha- 

 nics, one of the simple powers, which 

 serves to find out the equality or differ- 

 ence of weight in heavy bodies. See ME- 

 CHANICS. 



BALLANCE of trade, a term applied to 

 the money ballance to be paid by one na- 

 tion trading and carrying on business 

 with another. So far as the articles mu- 

 tually exported and imported pay for each 

 other, there is no ballance ; but on which 

 ever side the exports fall short in their 

 amount, that nation is said to have the 

 ballance of trade against it. See TRADE. 



BALLANCE, hydrostatical. See HYDRO- 

 STATICS. 



BALLANCE of a clock or -watch. See 

 CLOCK-WORK and WATCH-WORK. 



BALLANCE, to, in sea-language, to con- 

 tract a sail into a narrower compass, and 

 the term is applied particularly to the 

 mizen of a ship, and the main sail of those 

 vessels in which it is extended by a boom. 

 The operation of balancing the mizen is 

 performed by lowering the yard a little, 

 then rolling up a small portion of the sail 

 at the upper corner, and lashing it about 

 one-fifth down towards the mast. A boom- 

 sail is ballanced by rolling up a portion of 

 the clue, or lower aftermost corner, and 

 fastening it strongly to the boom. 



BALLAST, a quantity of stones, gravel, 

 or sand, laid in a ship's hold, to make her 

 sink to a certain depth into the water, 

 and sail upright, rendering her of a pro- 

 digious weight. The ballast is sometimes 

 one-quarter, one-third, or one half, ac- 

 cording to the difference of the bulk of 

 the ship. Flat vessels require the most 

 ballast. Ships are said to be in ballast, 

 when they have no other loading. Mas- 

 ters of vesselsare obliged to declare the 

 quantity of ballast they bear, and to un- 

 load it at certain places. They are pro- 

 hibited unloading their ballast in havens, 

 roads, &c. the neglect of which prohibi- 

 tion has ruined many excellent ports. 

 All ships and vessels taking in ballast on 

 the river Thames are bound to pay the 

 corporation of the Trinity-house, for 

 every ton carried to any ship in the coal 

 trade, Is. and for every other British ship, 

 Is. 3d. For every ton carried to any 

 foreign ship, Is. 7d. The Trinity-house 

 employ men, and regulate them, and their 



