FO U 



every equivalent of sulphur, a comma is 

 placed over the symbol ; thus C repre- 

 sents carbonic acid; K, sulphuret of 



potassium ; K N. nitrate of potassa. 



FO'RMYL. A hypothetical radical of 

 a series of compounds, one of which is 

 formic acid. 



FORNAX CHEMICA. The Chemist's 

 Furnace ; a modern southern constella- 

 tion, consisting of fourteen stars, and 

 situated immediately below Cetus. 



FORNIX. Literally, an arch ; a term 

 applied to an assemblage of small plates, 

 or lamellae, which overarch the orifice of 

 the tube of the flower in certain plants, 

 as cynoglossum. 



FO'RSTERITE. A crystallized mine- 

 ral containing silica and magnesia, found 

 atVesu vius, accompanied by pleonaste and 

 pyroxene, and named from Mr. Forster. 



FO'SSIL {fossilis, dug out of the 

 earth). Any thing dug out of the earth. 

 The term is now restricted to " organic 

 remains," or the petrified remains of ani- 

 mal and vegetable substances found im- 

 bedded in the strata of the earth. 



FOSSIL COPAL. Highgate resin. A 

 mineral of a resinous odour, found in the 

 bed of blue clay at Highgate, near Lon- 

 don, and at Wocklow in Moravia. 



FOSSILI'FEROUS {fossilis, dug out 

 of the earth, fero, to bear). A term ap- 

 plied to a formation or rock containing 

 organic remains, or fossils, while those 

 rocks in which no such relics are found 

 are called non-fossiliferous. 



FOSSO'RES {fossor, a digger). Dig- 

 gers ; a general term for a group of acu- 

 leate hymenopterous insects, comm.only 

 known as sand and wood wasps, which 

 dig cells in the earth or in wood, for the 

 deposition of their eggs and stores. 



FOUNDING. The mechanical art 

 which comprises all the operations of 

 reducing ores, and of smelting and cast- 

 ing metals. 



FOURTH. One of the harmonica! 

 intervals of music, containing four sounds 

 or terms between its extremes, and three 

 intervals ; or as being the fourth in order 

 from the fundamental sound in the na- 

 tural or diatonic scale. The diminished 

 fourth consists of a whole tone and two 

 semitones; the perfect fourth, of two 

 whole tones and a semitone ; the super- 

 fluous fourth, extreme sharp, or tritonus, 

 of three whole tones. 



FOUSEL OIL. Hydrate of oxide of 

 cmyl. Oil of grain-spirits or potatoes 

 142 



FR A 





an oil produced in the fermentation of 

 unmalted grain and potatoes. 



FOVI'LLA. A viscous liquor con- 

 tained in the pollen-vesicle of plants. 



FRACTION (fractio, a breaking). An 

 arithmetical quantity which represents a 

 part or parts of an integer, or whole 

 number. A vulgar fraction is expressed 

 by means of two numbers placed one over 

 the other, with a line between them ; the 

 lower of these is the denominator, and 

 shows into how many equal parts the 

 integer is divided ; the upper is the nu- 

 merator, and shows how many of these 

 parts are taken to form the fraction, as |. 



1. A proper fraction is one whose nu- 

 merator is less than the denominator, and 

 which is itself therefore less than the 

 whole in question, as f. An improper 

 fraction is one whose numerator is equal 

 to or greater than the denominator, and 

 which is itself therefore equal to or 

 greater than the whole in question, as 



i, V- 



2. A mixed number is one formed of a 

 whole number and a fraction, as 2§. A 

 compound fraction is a fraction of a frac- 

 tion, as f of §. A complex fraction is one 

 in which either the numerator or deno- 

 minator, or both, are fractions, as — 



3^ ^ 1| g of 3 

 '2^ 4 1' 3|' 2i ' 



3. A continued fraction is one whose 

 denominator is continued by being itself 

 a mixed number, and the denominator of 

 the fractional part again continued as 

 before, and so on ; as — 



1 5 1 



"T' "T 1 



2+ 3-f— P + 



1 9-J-&C. 1 



3 + — g + — • 



4 r + &c. 



4. A vanishing fraction is one in which 

 a supposition is made which destroys 

 both numerator and denominator at the 

 same time ; thus, 



x2 — 1 



x—l 



is a fraction which will assume the form 



of _, when x = I. 

 

 FRACTURE {fractura, a breaking). 

 A term employed in geology to designate 

 the appearance of a fresh surface of a 

 rock, when exposed by the stroke of a 

 hammer or any other forcible separation 

 of its parts. It may be even, or form a 

 plane of greater or less extent ; uneven, 

 or formed of variously inclined planes of 



