|Hutton, Charles Mathematical and Philosophical Dictionary 1795|
generally kindle the combustible bodies in contact with it, because the time of its inflammation is too short.
Fulminating Damp. See Damp.
, or Fulguration, a vehement noise or shock resembling thunder, caused by the sudden explosion and inflammation of divers preparations; as aurum fulminans, &c, when set on fire.
, a term used in analytics, for an algebraical expression any how compounded of a certain letter or quantity with other quantities or numbers: and the expression is said to be a Function of that letter or quantity. Thus , or , or , or xc, or cx, is each of them a Function of the quantity x.
On the subject of Functions, their divisions, transformations, explication by insinite series, &c, see Euler's Analys. Infinitorum, c. 1, where the subject is fully treated.
, an English long measure, containing 660 feet, or 220 yards, or 40 poles or perches, or the 8th part of a mile.
, in Dialling, certain additional points and lines drawn on a dial, by way of ornament. Such as the signs of the zodiac, length of days, parallels of declination, azimuths, points of the compass, meridians of chief cities, Babylonic, Jewish, or Italian hours, &c.
, in Architecture, a small round member cut in form of a collar, with oval beads, under the <*>chinus, or quarter-round, in the Doric, Ionic, and Composite capitals.
, or Fusy, in Watch-work, is that part resembling a low cone with its sides a little sunk or concave, which is drawn by the spring, and about which the chain or string is wound.
The spring of a watch is the first mover. It is rolled up in a cylindrical box, against which it acts, and which it turns round in unbending itself. The chain, which at one end is wound about the Fusee, and at the other fastened to the spring-box, disengages itself from the Fusee in proportion as the box is turned. And hence the motion of all the other parts of the spring-watch. Now the effort or action of the spring is continually diminishing from first to last; and unless that inequality was rectified, it would draw the chain with more force, and wind a greater quantity of it upon the box, at one time than another; so that the movement would never keep equal time.
To correct this irregularity of the spring, it was very happily contrived to have the spring applied to the arms of levers, which are continually longer as the force of the spring is weaker: this foreign assistance, always increasing as it is most needed, maintains the action and essect of the spring in an equality.
It is for this reason then that the Fusee is made tapering somewhat conical, its radius at every point of the axis answering to the corresponding strength of the spring.
Now if the action of the spring diminished equally, as the parallels to the base of a triangle do; the cone, which is generated of a triangle, would be the precise figure required for the Fusee; but it is certain that the weakening of the spring is not in that proportion; and therefore the Fusee should not be exactly conical; and in fact experience shews that it should be a little hollowed about the middle, because the action of the spring is not there sufficiently diminished of itself.
Mr. Varignon has investigated the figure of the Fusee, or the nature of the curve by whose revolution about its axis, shall be produced the solid whose figure the Fusee is to have. This curve it may easily be shewn is an hyperbola whose asymptote is the axis of the Fusee. Thus, let DFE be the curve of the Fusee, its axis being ABC: let AD express the greatest strength of the spring when the watch is quite wound up, o<*> when the spring acts at D, and BG the least strength when the watch is down, or when the spring acts at E; so as that , or ; join DG, produeing it to meet the axis produced in C; then shall HI denote the strength of the spring acting at the corresponding point F of the Fusee; and the nature of it must be such that the rectangle be equal to a constant quantity, or HF must be reciprocally as HI, or ; but because - - AD, HI, BG, are directly proportional to - CA, CH, CB, theref. these are reciprocally propor. to AD, HF, BE, and consequently the curve DFE is an hyperbola, whose centre is C, and asymptotes AC and KL: so that the figure of the Fusee is the solid generated by an equilateral hyperbola revolved about its asymptote. See also Martin's Mathem. Instit. vol. 2, p. 364.
, Fuse, or Fuze, in Artillery, is a woode<*> tap or tube used to set fire to the powder in a bombshell. The bore of this tube is filled with a composition, of sulphur one part, saltpetre 3 parts, and mealed powder 3, 4, or 5 parts. The tube is driven hard into the hole in the shell, having first cut it to the exact length answering to the time of the intended flight of the shell, so that, the composition in the Fuse catching fire by the discharge of the shell from the mortar, it just burns down to its lower end, and so sets fire to the powder in the shell, and thereby bursts it, at the moment when it arrives at the end of its range or flight.
, in Architecture, the shaft of a column, or the part comprehended between the base and the capital, called also the Naked.
, or Fuzee. See Fusee.