400 FLAME 



FIRE-OPAL or Girasol. A lustrous variety of opal. See OPAL. 



FIRE STONE signifies a stone which will bear the heat of a furnace without injury. 

 In geology the term is generally applied to the sandstone which occurs at the top of 

 the Upper Greonsand in the south of England, which, from its power of withstanding 

 the effects of heat, is frequently used for lining kilns and furnaces. It is a greenish 

 calcareous sandstone, soft, and easily worked in any direction when first taken from 

 the quarry ; but, on exposure, it becomes extremely hard and durable, and well suited 

 for building purposes. Many of the older churches in Dorsetshire are built of this 

 stone. H.W.B. 



FIRE-WORKS. See PTEOTECHNT. 



FIR-WOOD. The wood of several species of conifers, the most important of 

 which are the Silver Fir, Abies excelsa, or the Pinus abies of Linnaeus (Sapin commun, 

 Fr. ; Weiss or Edd Tanne, Ger.) ; and the Scotch Fir, Pinus sylvcstris (Pin d'Ecosse, 

 Fr. ; Kiefcr, or Fohre, Ger.). These are valuable as timber-trees, and for the resinous 

 juices which exude from them. See ABIES ; TURPENTINE. 



FISCHERITE. A hydrous silicate of alumina, from Nischne-Tagilsk in the Urals. 



FISH. Many of the parts of fish enter into manufactures, and, prepared, become 

 articles of commerce. The 'sound' or swimming-bladder of the sturgeon yields isin- 



flass, but the true isinglass is sometimes sophisticated by the gelatin of common fish, 

 ish-oil finds employment in many ways, and manures prepared from fish-offal are 

 much used. 



Owing to the arrangements made relative to our less important imports, it is not 

 possible to give as was given in the last edition our importation of fish. See 

 CAVAIRE; ISINGLASS; MANURE. 



FISH-SKIM'. The skin of the dog-fish, shark, and other ganoids, used occasionally 

 in polishing and in cleaning rounded and irregular works in pattern making. 



FISSURE. A crack or rent in rocks. See DYKE. 



FIXED AIR. An old name for carbonic-acid gas. 



FLAGSTONE. A stone which splits freely in a particular direction along the 

 original lines of deposition of the rock. These are generally sandstones, and the 

 splitting surfaces are frequently produced by thin lamina? of mica ; but thin bedded 

 limestones also furnish flagstones, of which some beds of Purbeck limestone and the 

 Stonesfield slates are examples. Flagstones are also obtained from Lias limestones, 

 which are, in fact, thin beds of indurated clay. H.W.B. 



Most of our common flagstones are micaceous sandstones from the coal-measures of 

 Yorkshire. 



FLAKE-WHITE. This name is applied indiscriminately to pure white lead, 

 and to the trisnitrite of bismuth. 



FXiAIVTE (Flammc, Fr. and Ger.), in the ordinary acceptation, is the combustion 

 of a mixture of an inflammable gas or vapour with air. That it is not, as many sup- 

 pose, combustion merely at the exterior surface where the gas and the air come 

 in contact with each other, is proved by passing a fragment of phosphorus or sulphur 

 into the centre of a large flame. Either of these bodies ignited in passing through 

 the film of flame will continue to burn there with its peculiar light ; thus proving 

 that oxygen is mixed with the vapour in the interior. If we mix good coal-gas with 

 .as much atmospheric air as can convert all its carbon into carbonic acid, the mixture 

 will explode with a feeble blue light; but if wo mix the same gas with a small 

 quantity of air, it will burn with a rich white flame : a knowledge of this fact has led 

 to the practice, in many of our large gas-works, of pumping air into the gasometers 

 with the coal-gas a dishonest and a dangerous system. In the latter case, the 

 carbonaceous particles are precipitated, as Sir H. Davy first showed, in the interior of 

 the flame, become incandescent, and constitute white light. Towards the interior of 

 the flame of a candle, a lamp, or a gas-jet, where the air is scanty, there is a deposition 

 of solid charcoal, which, by its ignition, increases in a high degree the intensity of the 

 light. If we hold a piece of fine wire gauze over a jet of coal-gas close to the orifice, 

 and if we then kindle the gas, it will burn above the wire with its natural brilliancy ; 

 but if we elevate the gauze progressively higher, so as to mix more and more air with 

 it before it reaches the burning point, its flame will become fainter and less white. 

 At a certain distance it becomes blue, like that of the above explosive mixture. If a 

 few platina wires be held in that dim flume they will grow instantly white hot. and 

 illuminate the apartment. On reversing the order of this experiment, by lowering 

 progressively a flat piece of wire gauze from the summit towards the base of a i_ r as 

 flame, we shall find no charcoal deposited at its top, because plenty of air has been 

 introduced there to convert all the carbon of the gas into carbonic acid ; but. as AVO 

 descend, more and more charcoal will ;i|.p.-:ir upon the mcshc*. At the very bottom, 

 indeed, where the atmospheric air impinges upon tho gau/e, the llaine is blue, and no 

 charcoal can therefore be deposited. 



