FLU 



FLU 



rows of cells united together, and woven 

 like a mat. About eighteen species have 

 been described. 



FLUTE, an instrument of music, the 

 simplest of all those of the wind kind. It 

 is played on by blowing it with the mouth, 

 and the tones or notes are changed by 

 stopping and opening the holes disposed 

 for that purpose along its side. The an- 

 cient fistulae, or flutes, were made of 

 reeds, afterwards of .wood, and last of me- 

 tal ; but how they were blown, whether as 

 our flutes, or as hautboys, does not appear. 



FLUTE, German, is an instrument en- 

 tirely different from the common flute. It 

 is not, like that, put into the mouth to be 

 played, but the end is stopt with a tam- 

 pion or plug ; and the lower lip is appli- 

 ed to a hole about two inches and a half, 

 or three inches, distant from the end. 

 The instrument is usually about a foot 

 and a half long; rather bigger at the up- 

 per end than the lower : and perforated 

 with holes, besides that for the mouth, 

 the lowest of which is stopped and open- 

 ed by the little finger's pressing on a 

 brass, or sometimes a silver key,like those 

 in hautboys, bassoons, &c. Its sound is 

 exceedingly sweet and agreeable ; 'and 

 serves as a treble in a concert. 



FLUX, a general term made use of to 

 denote any substance or mixture added to 

 assist the fusion of minerals In the large 

 way, limestone or fluor spar are used as 

 fluxes ; but in small assays, the method of 

 the great operations is not always follow- 

 ed, though it would be very frequently of 

 advantage to do so. The fluxes made use 

 of in assays, or philosophical experiments, 

 consist usually of alkalies, which render 

 the earthy mixtures fusible, by converting 

 them into glass ; or else glass itself into 

 powder. 



Alkaline fluxes are either the crude 

 flux, the white flux, or the black flux. 

 Crude flux is a mixture of nitre and tartar, 

 which is put into the crucible with the 

 mineral intended to be fused. The deto- 

 nation of the nitre with the inflammable 

 matter of the tartar is of service in some 

 operations ; though generally it is attend- 

 ed with inconvenience, on account of the 

 swelling of the materials, which may 

 throw them out of the vessel, if proper 

 care be not taken either to throw in only 

 a little of the mixture at a time, or to pro- 

 vide a large vessel. 



White flux is formed by projecting 

 equal parts of a mixture of nitre and tar- 

 tar, by moderate portions at a time, into 

 an ignited crucible. In the detonation 

 which ensues, the nitric acid is decom- 



posed, and flies off with the tartarous acid, 

 and the remainder consists of the potash 

 in a state of considerable purity. This has 

 been called fixed nitre. 



Black flux differs from the preceding, 

 in the proportion of its ingredients. In 

 this the weight of the tartar is double that 

 of the nitre ; on which account the com- 

 bustion is incomplete, and a considerable 

 portion of the tartarous acid is decom- 

 posed by the mere heat, and leaves a quan- 

 tity of coal behind, on which the black 

 colour depends It is used where metallic 

 ores are intended to be reduced, and ef- 

 fects this purpose by combining with 

 the oxygen of the oxide. 



There is danger of loss in the treat- 

 ment of sulphurous ores with alkaline 

 fluxes : for, though much or the greater 

 part of the sulphur may be dissipated by 

 roasting, yet that which remains will form 

 a sulphuret with the alkali, which is a very 

 powerful solve tit of metallic bodies. The 

 advantage of M. Morveau's reducing flux 

 seems to depend on its containing no un- 

 combined alkali. It is made of eight 

 parts of pulverized glass, one of calcined 

 borax, and half a part of powder of char- 

 coal. Care must be taken to use a glass 

 which contains no lead. The white glasses 

 contain in general a large proportion, and 

 the green bottle glasses are not perhaps 

 entirely free from it. 



FLUX, in medicine, an extraordinary 

 issue, or evacuation of some humours of 

 the body. See MEDICINE. 



FLUXION, in mathematics, denotes 

 the velocity by which the fluents or flow- 

 ing quantities increase or decrease ; and 

 may be considered as positive or nega- 

 tive, according as it relates to an incre- 

 ment or decrement. 



The doctrine of fluxions, first invented 

 by sir Isaac Newton, is of great use in the 

 investigation of curves, and in the disco- 

 very of the quadratures of curvilinear 

 spaces, and their ratifications. In this 

 method, magnitudes are conceived to be 

 generated by motion, and the velocity of 

 the generating motion is the fluxion of 

 the magnitude. Thus, the velocity of the 

 point that describes a line is its fluxion, 

 and measures its increase or decrease. 

 When the motion of this point is uniform, 

 its fluxion or velocity is constant, and may 

 be measured by the space described in a 

 given time ; but when the motion varies, 

 the fluxion of velocity at any given point 

 is measured by the space that would be 

 described in a given time, if the motion, 

 was to be continued uniformly from that 

 term. 



