FLUX 



Flux. Term used in metallurgy. 

 Comparatively few metals present 

 themselves in nature in the metallic 

 form, or native, to use the metal- 

 lurgical term ; most are combined 

 with other elements, the combina- 

 tion forming an ore. These ores are 

 often difficult to melt, and are 

 smelted by the aid of fluxes. 



The chief fluxes are lime or 

 limestone, common salt, sodium 

 carbonate, clay, silica, borax 

 litharge, nitre, carbon, argol or bi- 

 tartrate of potash, flour, starch, and 

 potassium cyanide, while argol and 

 nitre are used in combination toform 

 "black" and "white" fluxes. See 

 Metallurgy; Smelting. 



Fluxion. Term used by Sir 

 Isaac Newton to signify the rate or 

 proportion at which a variable (or 

 flowing) quantity increased its 

 magnitude The fluxion is now 

 usually regarded as the differential. 

 See Differential Calculus ; Newton. 

 Fly. Insect of the order known 

 as Diptera from being charac- 

 terised by the possession of only 

 two wings. 

 The fore 

 wings alone 

 remain as 

 flying or- 

 gans, the 

 hind ones 

 having b e- 

 c o m e r e- 

 duced to two 

 small balan- 

 cers resem- 

 bling drum- 

 sticks and known as halleres, upon 

 which depends the insect's power of 

 balancing itself in the air ; if they 

 are removed, the flight at once be- 

 comes unsteady. 



The wings are without scales and 

 usually hairless, but strongly 

 veined. The buzzing sound is pro- 

 duced by the rapid vibration of the 

 wings in flight, which often 

 amounts to 600 beats in a second. 

 The jaws have been modified to 

 form piercing or sucking instru- 

 ments or both, and the insect feeds 

 entirely on fluids. In the biting 

 species, as gnats and horse-flies, the 

 mouth is provided with a pair of 

 sharp lancets contained in the pro 

 boscis. The feet of many flies have 

 pads covered with minute sucker- 

 like hairs, with which they can 

 walk upside down or ascend the 

 glass of window-panes. 



Flies pass through a complete 

 series of metamorphoses. The eggs 

 are usually deposited in situations 

 where the young may find a supply 

 of food ready to hand, and the 

 larvae are in many cases small 

 white maggots without apparent 

 head, as those of the house-fly and 

 the blue-bottle. In other species, as 

 the gnats, they are aquatic and are 



L..J 



Fly. Foot of house- 

 fly highly magnified 



Fly. 1 and 2. House tiy. Musca domestica. 3. Girdled drone fly, Volucella 

 inanis. 4. Gold-girdled fly, Cbrysotoxum bicinctum. 5. Dung fly, Scatophaga 

 stercoraria. 6. Humble-bee fly, Bombylius major. 7. Bacon fly, Policies 

 lardarius. 8. Humble-bee's drone fly, Volucella bombylans. 9. Noontide fly, 

 Mesembrina meridiana. 10. Hornet fly, Asilus crabroniformis. 11. Hump- 

 backed fly, Ogcodes gibbosus. 12. Great Bristly fly, Tachina grossa. 13. Pupae 

 and, 14, maggots of house-fly 



1, Nat. Hitt. Mut., S. Kensington; 13 and 14, Pub. Health Dept., Liverpool 



variously modified to suit their 

 mode of life. In a few species the 

 larvae are parasitic and live in the 

 bodies of their hosts. See Insect ; 

 also Bot-fly, illus. 



Fly. Word used for a hackney 

 cab, presumably on account of the 

 fact that its speed, when intro- 



Fly-agaric. the large toadstool. 

 Amanita inuscaria 



duced, was, comparatively speak- 

 ing, considerable. The space above 

 the proscenium in a theatre, from 

 which the scenes, etc., are con- 

 trolled, is called the flies. See Cab ; 

 Theatre. 



Fly. Largest known river of 

 New Guinea or Papua. It rises 

 among the Victor Emmanuel Mts. 

 in the E. part of the island, and 

 flows S.W. and then S.E. to dis- 

 charge its waters into the Gulf of 

 Papua by a long, wide estuary. 

 For part of its course it forms the 

 frontier between Dutch and British 

 New Guinea. It has a length of 

 about 620 m., and is navigable 

 for small craft for nearly the 

 whole of its course. The principal 

 affluents are the Alice and Strick- 

 land rivers. 



Fly-agaric (Amanita inuscaria). 

 Large toadstool of the family 

 Agaricinae. It has a creamy -white 

 stem and gills, the former with a 

 broad soft frill around its upper 



