FIR 



[174] 



F I S 



thanks of mankind." Fire-datnp, 

 or carburetted hydrogen gas, ap- 

 pears to be generated by the de- 

 composition of iron pyrites in coal, 

 and may often be heard issuing 

 from the fissures in coal-beds with 

 a bubbling noise, as it forces the 

 water out with it. In Messrs. 

 Coriybeare and Phillips' Geology of 

 England and Wales, it is stated 

 that the pit-men occasionally open 

 with their picks, crevices in the 

 coal or shale, which emit 700 

 hogsheads of fire-damp in a minute. 

 These blowers, as they are termed, 

 continue in a state of activity for 

 many months together. The after- 

 damp, or stythe, which follows the 

 explosions, is a mixture of the car- 

 bonic acid and azotic gases, re- 

 sulting from the combustion of the 

 carburetted hydrogen in atmos- 

 pheric air, and more lives are de- 

 stroyed by this than by the violence 

 of the fire-damp explosions. Sir 

 H. De La Beche observes, "it 

 appears very remarkable that in 

 the coal districts of the British 

 Isles, where such a large amount 

 of carburetted hydrogen is annually 

 produced, means have not been 

 adopted for making an economical 

 use of this gas, both as repects 

 light and heat." 



TIRE OPAL. Called also Girasole. The 

 Feur Opal of Klaproth; Quartz 

 Besinite Girasol of Haiiy. A sub- 

 species or variety of opal, according 

 to some authors, of a hyacinth-red 

 colour, but according to others pre- 

 senting bright hyacinth- red and 

 yellow colours, when turned to wards 

 the light. It has been hitherto 

 obtained chiefly from Mexico and 

 the Faroe Islands. See Girasole 

 and Opal. 



FIRE-STONE. (The craie chloritee, ou 

 glauconie crayeuse, of the French 

 geologists.) Known also as the 

 Merstham beds ; and Upper Green 

 sand. From the application of the 

 stone found in some parts of this 



deposit in the construction of fur- 

 naces, ovens, &c., it has obtained 

 the name of fire-stone. An aren- 

 aceo-argillaceous deposit of a grey- 

 ish green colour, composed of marl 

 and grains of silicate of iron ; in 

 some places, in a state of sand ; in 

 others, forming a stone sufficiently 

 hard for building. The transition 

 from the marl to the fire-stone is in 

 many localities so gradual, and the 

 sandy particles are so sparingly 

 distributed, that the chalk-marl 

 may be said to repose immediately 

 on the gait; in others, however, 

 the characters of the fire-stone are 

 very peculiar, and some geologists 

 have deemed them of sufficient 

 importance to rank this deposit as 

 an independent formation. The 

 fire-stone contains the same fossils 

 as the grey-marl, and a few species 

 not found in any other bed. Dr. 

 Mantell. 



FI'SSILE. ffissilis, Lat.) Capable of 

 being split, or divided, in the 

 direction of the grain or cleavage. 



FISSIRO'STRES. A family of birds, nu- 

 merically small, but very distinct 

 from all others in the beak, which 

 is short, broad, horizontally flatten- 

 ed, slightly hooked, unemarginate, 

 and with an extended commissure, 

 so that the opening of the mouth 

 is very large, which enables them 

 to swallow with ease the insects 

 they capture while on the wing: 

 the swallow belongs to this family, 

 and is an example. 



FISSURE'LLA. A gasteropod ; a genus 

 of the order Scutibrancbiata. A 

 buckler-formed univalve, without 

 spire : the vertex perforated by a 

 small ovate or oblong orifice, which 

 affords a passage to the water re- 

 quired for respiration ; this orifice 

 penetrates into the cavity of the 

 branchiae, which are situated on 

 the fore part of the back. The 

 fissurella has been found in the 

 Essex cliffs. 



FISTULA'.N A. A genus of the family 



