FUEGO 



FUEL 



Quercus marina of ancient pharmacy being F. 

 serratus, and the ^Ethiops vegetabilis the charred 

 residue of this and its allies. An alcoholic extract 

 is also frequently advertised for the treatment of 

 corpulence. 



The genus Fucus and a few closely allied 

 genera (e.g. Fucodium, Himanthalia, Cystoseira, 

 and notably Sargassum, specially described under 

 GULF-WEED), form the family Fucacese, which 

 are the highest, and with the allied Lamin- 

 ariacese, also the most familiar representatives 

 of the large alliance of brown seaweeds (see 

 the article SEAWEEDS). The vegetative body 

 is usually a thallus, yet in Sargassum, &c., a 

 distinction of this into stem and leaves is very 

 complete. The branching of Fucus is dichotom- 

 ous in one plane. Of the inner or medullary cells 

 of the thallus, the outer wall becomes mucilagin- 

 ous, while the less superficial of the rind cells 

 develop filaments which grow inwards, so surround- 

 ing the inner cells within a network of filaments. 

 The bladders are formed by the simple separation 

 of portions of the tissue, the cavities becoming 

 distended by air. A sexual multiplication may be 

 said to be absent, but sexual reproduction is easily 

 observed. A large area at the end of the frond 

 becomes covered with small depressions, which are 

 overgrown until they are spherical flasks with only 

 a minute opening on the surface. The cells lining 

 this flask or conceptacle proceed to divide, and 

 many form barren cellular filaments which, how- 

 ever, instead of turning inwards, as in vegetative 

 growth, grow into the cavity of the flask or even 

 project beyond it as a tuft of hairs. But many 

 are arrested in division while still only two-celled, 

 and the upper of these cells enlarges greatly. In 

 some forms (Cystoseira, Himanthalia) this becomes 

 the ovum, but in others its contents divide into 

 two, four, or in Fucus eight ova ; hence it is 

 termed the oogonium. Other filaments again not 

 only lengthen, but branch freely. Their terminal 

 cells become antheridia i.e. their protoplasm 

 divides into a multitude of spermatozoids. Fer- 

 tilisation takes place when the ripe fertile fronds 

 are left bare by the tide, the change of specific 

 gravity through evaporation doubtless being of 

 importance in aiding the escape of the sexual 

 products. The outer membrane of the oogonium, 

 like that of a medullary cell, becomes mucilaginous 

 and gives way, and the groups of eight ova, still, 

 however, enclosed within the inner wall, escape 

 from the conceptacle ; the antheridia, too, break off 

 and escape to the opening of the conceptacle ( per- 

 haps helped by the slight contraction of the volume 

 of this which evaporation must tend to produce ). 

 When the tide returns, both ova and spermatozoids 

 break completely free and fertilisation takes place. 

 Cross-fertilisation, always possible even where, as 

 in F. platycarpus, the same conceptacle develops 

 ova and spermatozoa, becomes perfect in the more 

 familiar species, of which the greater prevalence 

 thus becomes more intelligible. The fertilised ovum 

 soon develops a wall, becomes attached, and pro- 

 ceeds to divide and lengthen, soon forming a root- 

 like attachment at one end, a growing point at the 

 other. See SEAWEEDS ; also special articles above 

 mentioned. 



FllCgO, TlERRA DEL. See TlERRA DEL 



FUEGO. 



Fuel. The chief mode of artificially producing 

 that condition of matter which is called heat is by 

 burning certain substances in air. These substances 

 contain carbon and hydrogen, which during the 

 chemical change implied by burning unite with the 

 atmospheric oxygen, and as the temperature rises 

 emit light as well as heat. Since these two 

 elements are very widely distributed in nature, the 



classification of all the compounds which may be 

 termed fuels is somewhat difficult. After using 

 wood for long ages men at last laid the mineral 

 kingdom under requisition, but the fuels thence 

 derived were soon recognised to be undoubtedly 

 of vegetable origin. Some writers include all these 

 under the term natural, and distinguish such 

 derivatives as coke, charcoal, and combustible 

 gases as artificial. Popularly, fuels are a large 

 class of compounds, all of vegetable origin except 

 the animal oils and fats, which produce heat and 

 light when raised to ' kindling temperature.' Thus, 

 besides coal and coke, wood and charcoal, and peat 

 or turf, we must reckon tallow, wax, alcohol, coal 

 and other gases, petroleum, creasote or ' dead -oil,' 

 and others as fuels. To be exhaustive, we should 

 further refer to a sub-class called ' patent ' fuels. 



The ordinary solid fuels fall under two heads : 

 those containing water in a large proportion e.g. 

 wood, turf, and most coals and therefore pro- 

 ducing, when burned, hydrogen as well as carbon ; 

 and secondly, those which are purely carbonaceous 

 coke, charcoal, and anthracite. In recent times, 

 since metallurgy has assumed such proportions in 

 all countries, and especially since the application of 

 steam-power, the coxing of coal has been more and 

 more perfected, in order to concentrate the carbon 

 and present a fuel capable of producing a higher 

 temperature. Wood as a fuel is either light and 

 soft, as deal, or heavy and hard, as oaK ; but 

 neither kind is now applied in metal-working, 

 unless in the concentrated form of charcoal. Wood 

 contains so large a proportion of water as to reduce 

 its heat-giving quality both in quantity and in- 

 tensity, and contains less than half its weight of 

 carbon ( see table ). 



Charcoal is formed by condensing the carbon of 

 wood and expelling the hydrogen and oxygen, just 

 as coke is a concentration of coal by an analogous 

 process. When the wood has been packed and so 

 closed in as to prevent access of air, by raising the 

 whole to a temperature of about 300, the wateiy 

 and gaseous particles are entirely expelled, and a 

 mass of almost pure carbon remains. Similarly from 

 coal we have coke, prepared by ' dry distillation ' or 

 imperfect combustion, so as to retain the carbona- 

 ceous part in a concentrated state and set free the 

 volatile ingredients and part of the sulphur. A 

 special property of coke for metallurgy, as compared 

 with coal, is that, when exposed to high tempera- 

 tures as in iron-blast furnaces, it does not become 

 pasty. 



Turf or peat is an agglomeration of decayed 

 vegetable matter, such as is frequently found on 

 the sites of ancient forests. It is remarked that 

 no instance of its formation occurs within the 

 tropics ; though Lyell describes the Great Dismal 

 Swamp between Virginia and North Carolina to 

 be a mass of black peat-like matter, 15 feet deep. 

 Some peaty sediment has also been noted in a 

 Cashmere lake. From holding so small a percent- 

 age of carbon, turf is of little use in the arts ; but 

 in Bavaria it has been utilised for locomotive 

 engines after being compressed into bricks, and in 

 some districts it has been converted into a species 

 of charcoal. 



Superior to the peat fuels, though still inferior in 

 carbon to coal proper, are the lignites or brown 

 coal, which occur in geological deposits of more 

 recent formation than the true coal-measures. The 

 lignites contain a larger proportion of water than 

 coals properly so termed ; and are of so many 

 varieties as gradually to pass into the bituminous 

 class, which are known by their smoky flame and 

 derive their name, not from any bitumen in their 

 composition, but from the well-known tars which 

 they produce. With the bituminous must be 

 reckoned the 'coking coal' and the 'cannel (i.e. 



