F L 



L 180] 



FOR 



certain rocks to split, foliate^ or 

 cleave in a certain given direction ; 

 by foliation is meant, a separation 

 into layers of different chemical 

 composition, while cleavage means 

 only a tendency to split, in a mass 

 of the same composition. 



FO'LKSTONE MAEL. A stiff marl, 

 varying in colour from a light 

 grey to a dark blue, more gene- 

 rally known under the provincial 

 term Gait. The thickness of this 

 bed is in some places, in the South 

 of Sussex, not less than between 

 two and three hundred feet. It is 

 a member of the cretaceous group, 

 lying between the upper and lower 

 green-sand. Where the Folkstone 

 marl is exposed, and forms the 

 surface of the country, the soil is 

 exceedingly tenacious, and ranks 

 amongst the finest and most pro- 

 ductive. The Folkstome marl 

 abounds in fossils. 



FO'LLICLE. (folliculus, Lat. follicule, 

 Fr.follicoh, It.) 



1. In botany, a univalvular peri- 

 carp, opening on one side longitu- 

 dinally, and having the seeds loose 

 in it ; a membranous seed-vessel of 

 one valve and one cell, bursting 

 lengthwise, and having no apparent 

 suture to which the seeds are 

 attached. 



2. In anatomy, a small secreting 

 cavity. 



FONTANE'L. (fontanelle, T?r.fontanella, 

 It.) An opening left in the skull 

 at birth, which is subsequently 

 closed by osseous deposit; there 

 are two fontanels. 



FORA'MEN. (Lat.) A hole ; an 

 opening ; generally, by which 

 nerves or blood vessels obtain a 

 passage through bones. In botany, 

 the opening in the ovulum. When 

 the foramen is visible on the seed, 

 as is the case in the bean and pea, 

 it is called the micropyU. 



FOBA'MINATED. } (from for ammo, Lat.) 



FORA'MINOTJS. ) Pierced with small 



openings; full of small holes; 

 porous. 



FOBAMINI'FEEA. The second order of 

 the class Astomata, comprising 

 Rotalia, Nodosaria, Nummulites, 

 and Orbitolites. This order has 

 been constituted a class by Pictet 

 and D'Orbigny, and divided into 

 seven families. 



FOEAMINI'FEEOUS. Belonging to the 

 order foraminifera. 



FO'ECIPATED. (forcipatm, Lat.) Hook- 

 ed, or furnished with pincers, as 

 the claws of a lobster, crab, &c. 



FOBMA'TION. (formatio, Lat. forma- 

 tion, Fr. formazione, It.) Any 

 assemblage of rocks possessing some 

 character in common, either as 

 regards their age, origin, or compo- 

 sition. When a series of strata 

 of a similar rock are arranged with 

 occasional strata intervening, of 

 rocks of another kind, which recur 

 in different parts of the series, they 

 are regarded as having been all 

 formed nearly at the same epoch, 

 and under similar circumstances; 

 and such series are called by 

 geologists formations. Thus, the 

 strata of shale, sand-stone, and 

 iron-stone, that accompany beds of 

 coal, are called the coal formation. 

 Strata of different kinds, in which 

 a gradation is observed into each 

 other, and which contain similar 

 species of organic remains, con- 

 stitute a geological formation. The 

 chalk with flints above, the lower 

 chalk without flints, the chalk- 

 marl, and the green-sand under the 

 chalk, are all regarded as members 

 of the chalk formation. Bakewell. 



FO'ENICATED. (fornicatus, Lat.) Con- 

 cave within, and convex without ; 

 vaulted; arched. 



FO'BNIX. (Lat.) In conchology, the 

 excavated part under the umbo. It 

 likewise signifies the upper, or con- 

 vex shell in the ostrea. 



FORTIFICATION AGATE. The name 

 given to a variety of agate which, 

 when cut and polished, presents 



