71 



FORMATION. 



FRACTURE. 



FORMATION, a geological term subordinate to 'system,' and 

 including special ' groups,' or assemblages of strata ; in a looser tense 

 it applies also to pyrogenous rooks and mineral veins. 



FORMICA a genus of Insects belonging to the family Pormicida. 

 It is distinguished by having the foot-stalk of the abdomen composed 

 of a single joint, the mandibles triangular, and denticulated at the 

 edge. The females are destitute of a sting. This genus comprises 

 about a dozen British species, the largest of which in the Hill-Ant or 

 Horse-Ant, P. rufa. The neuters in this species are about one-third 

 of an inch long, of a black colour, with the thorax, abdominal scale, 

 and a Urge part of the head, red. It makes its Urge conical nest in 

 the open ground in woods, &c., amassing together large quantities of 

 sticks, straws, Jtc. For a description of these nests see ANT. 



P. mtyuinea is of a blood-red colour, with the eyes and abdomen 

 black, and the wings dusky at the base. The neuter is similarly 

 coloured, except that the head ia darker. The male ia black, with 

 red legs. This species burrows iu wood, and is one of those 

 which steal the young of other species, rearing them to perform the 

 duties of the nest Two of the species subject to these marauders 

 are P. cunicularia and P. futca, both of which are inhabitants of this 

 country. The latter species ia of a shining black colour, with a alight 

 ashy tinge ; its form is rather long, and it is nearly smooth ; the 

 three or four basal joints of the antenna: are of a red colour, aa are 

 also the legs; the abdominal scale is large and triangular; aud the 

 ocelli are distinct. It establishes its nest under stones, moss, &e., 

 and at the foot of trees, the nest being entirely under ground. 



Among the exotic species of this genus are to be found many 

 which are extremely injurious or annoying in their habits. Of these 

 the Sugar- Ant of the West Indies ia perhaps the most extensively 

 prejudicial. P. taccharirora, as it is called, establishes its nest at the 

 root of sugar-canes, lime-trees and lemon-trees, where it loosens the 

 earth so that the trees are either blown down by the violent gales, or 

 so completely deprived of nourishment at the roots that they soon 

 die. Some years ago the injuries committed by this insect were so 

 great that a reward of 20,000?. was offered by the planters to any one 

 who should discover an effectual mode of destroying them, yet nothing 

 could be found to stay their ravages. The aid of fire was even 

 resorted to in vain; the insects rushing into the flames in such 

 myriads as to extinguish it. Heavy torrents of rain at last effected 

 their destruction. 



/'. intlefata, another exotic species, ia described by Colonel Sykes as 

 being an extraordinary instance of the operations of instinct in so low a 

 form of animal life. The fondness of these insects for sweet substances 

 is very great, and their attacks on such things were resisted in every 

 possible manner, yet although the table, on which the confectionary and 

 sweets were, was placed with its legs in water and removed a short dis- 

 tance from the wall, they succeeded in reaching them, to the great 

 astonishment of all, until the mode of access was discovered. Colonel 

 Sykes says, " I observed an ant upon the wall about a foot above the 

 level of the sweets ; it fell, and instead of passing between the wall and 

 the table and alighting upon the ground it fell upon the table." Others 

 followed its example with similar success; and it was no longer 

 a matter for doubt as to how they continued to swarm iu such 

 numbers about their favourite food, however carefully guarded. 



KOKMK'ID.E, an extensive family of Hymeuopterous Insects, 

 belonging to the section A culeala, and to the sub-section Jletcroyynn 

 of Latreille, comprising the Linmean genus Formica, or the numerous 

 tribes of Ants. The family is distinguished by the wingless state of 

 their abortive females, by the great length of the basal joint of the 

 antenna: in the females and the neuters, in which they are elbowed at 

 the extremity of this joint, and by the first or the first and second 

 joints of tho abdomen being knotted ; the upper lip of the neuters ia 

 large, horny, and perpendicular, falling between the jaws ; the eyea 

 are rounded, or oval and entire ; the jaws are large in many of the 

 species, the form of these organs varying greatly in many of the 

 species. In their structural character the Pormicida resemble the 

 Tiphitt and Doryli belonging to the section of the Sand- Wasps. The 

 neuters are smaller than the male*, and these are smaller than the 

 females; ; the abdomen in the first and last of these sexes is composed 

 of six segments, in the mole of seven. The females and neuters are 

 furnished with a sting in many of tho species. Those species which 

 have stings emit an irritating fluid into the wounds which they make, 

 while the stingiest species discharge a rrd transparent fluid on to the 

 skin, causing painful blisters. 



The various genera of this family, according to Latreille, are : 

 Formica, Polytryiu, Pmera, Myrmica, and Alia. This lust genus 

 differs from Myrmica only in having very short palpi ; the head of 

 the workers is generally very thick. Acepknlota it tho Visiting 

 Ant of the West Indies. [Axr; FORMICA; POLYKBUDS; PONKBA ; 



MlHMICA.j 



FORSTERITE, a Crystallised Mineral, the primary form of which 

 is a right rhombic prism. The crystals are colourless, translucent, 

 brilliant, and small; they are harder than quartz. This substance 

 occurs at Vesuvius accompanied by pleonastc and pyroxene. It has 

 not been accurately analysed, but contains silica and magnesia. 



IL was first found in the Ulue Clay at Highgntc, near 



II. COPAl 



London ; it occurs also at Wochlow in Moravia. 

 It occurs in irregular pieces or small nodular 



Its colour 



is yellowish or dull brown ; nearly opaque. Lustra resinous. Fracture 

 conchoidaL Specific gravity 1'046. When heated it yields an 

 aromatic odour, and melts into a limpid fluid; it burns with a >vll. in- 

 flame and much smoke. When strongly heated in contact with the 

 air, it is totally dissipated. 



FOSSILS. The term ' Fossil,' in its general acceptation, signifies 

 that which may be dug out of the earth. In this sense, antiquities, 

 as well as natural metallic and mineral bodies, may be said to be 

 fossils. But the word is generally used among geologists and minr- 

 ralogisU sometimes to designate simple and compound ininrnil 

 bodies, such as earth, salts, bitumens, and metals, but more generally 

 the petrified forma of plants and animals which occur in the strata 

 that compose the surface of our globe. Most of these fossil species, 

 many of the genera, and some of the families, are extinct ; and all of 

 them were considered in the darker ages to owe their origin to the 

 plastic power of the earth. They were named Lapidtt trftomorpAi, 

 L. fyurali, and, as their organic nature began to be suspected, L. 

 illluriani. Superstition was, in old times, busy with some of them, 

 the Belemnites and Ammonites for example. 



The appellation Pelrifacta, ' Petrifactions, 1 soon became common in 

 books and catalogues of cabinets, and then Sir John Hill's prop 

 to denominate such petrified bodies extraneous or adventitious 

 fossils, was adopted by many naturalists. Parkinson objected to 

 ' Petrifactions ' an a general term, and distinguished 'Fossils' by em- 

 ploying the expression ' Primary Fossils ' to denote those mineral 

 substances which are supposed to have been native, or, in other words, 

 to have existed primitively in the earth ; and by applying the appel- 

 lation 'Secondary Fossils' to the petrified exuviaa of plants and 

 animals. Though the terms of this last-mentioned writer are now no 

 longer adopted, he must always be considered as one of the fathers of 

 this branch of geology, a branch which William Smith first effectively 

 used as the key to the stratification. In the steps of Smith the first 

 writers on this subject have since trod ; and the study of ' Organic 

 Remains,' by which name the animal and vegetable bodies penetrated 

 by or converted into mineral substances are now known aa a whole, 

 has become of first-rate importance in deciphering the history of the 

 lithological structure of the earth's crust. The well-known Eocene, 

 Miocene, and Pliocene periods of Lyell, for instance, depend in a great 

 degree upon the proportionate absence or presence of living species 

 among the organic remains which have hitherto been discovered in 

 certain groups of strata of comparatively modern origin. 



Some notices of the fossil plants and animals, when snch are 

 known, are given in the articles which relate to existing families, 

 genera, or species; and extinct families, genera, and species are 

 treated of under their respective heads. 



FOSSORES, a family of the aculeatcd Ifymenoptera. [HVMKNOITERA.] 



FOUQUIERA'CEjE, a natural order of Plants belonging to 

 Lindley'a syncarpous group of Polypetalous Exngens. The species 

 are trees or shrubs, with entire oblong fleshy clustered leaves, seated 

 in the axil of a spine or n cushion, with scarlet flowers arranged in a 

 terminal spike or panicle. The sepals are 5, imbricated, ovate, or 

 roundish ; the petals 5, regular, combined in a long tube, arising from 

 the bottom of the torus or calyx ; the stamens 10 or 12, arising from 

 the same line as the petals, but distinct from them, exsertcd ; tho 

 anthers 2-celled ; the ovary superior, sessile ; the style filiform, trifid ; 

 the ovules numerous ; the capjule 5-cornered, 3-celled, 8-valved ; the 

 valves bearing the dissepiments in the middle; the seeds in part 

 abortive, compressed, winged, affixed to the axis ; the embryo strait, 

 in the centre of thin fleshy albumen ; the cotyledons flat. This order 

 was separated by De Candolle from Portutacete for the following 

 reasons : " 1, because the petals were iu a long tube of the same 

 nature as that of gnmopetalous Craitulacen- ; 2, because the capsule 

 consists of three loculicidal c^lls, that ia to say, which separate through 

 the middle, forming three septifcrous valves; and 3, because the embryo 

 is straight, with flat cotyledons, and stationed iu the centre of tl. -i,y 

 albumen." (Lindley, 'Nat. System.') In the structure of their flowers 

 Pouquirractr resemble Cramtlacetr ; and in the character of their fruit, 

 Loaiateir, Turneracett, and Stacl-hoiuriaretr. 



There are only two genera comprehended in this order : J'ou>]uirra, 

 named after Dr. Peter Edward Fouqtiiere, a professor of medicine nt 

 Paris ; and Bronnia, named in honour of Henry George lironn. 1m 

 has written on leguminous plant*. Each of these genera has a single 

 species : both plants are natives of Mexico. Of their properties little 

 is known. 



P.formoia is a showy shrub, and may be grown in a light rich soil, 

 and propagated by means of cuttings, which will root freely in mn.l 

 under a hand-glass in heat. Jlroitnia has been referred by some 

 botanists to Tamarieactir. 



(Lindley, Xatural Syttem ; Burnett, OiUtinft of Botany; Don, 

 liiihlnmydcoiu Plantt.) 



FOX.' [Vri.riDA] 



CI.OVK. [DmiTAi.is.] 

 UUAl'KS. [VlTls.] 



T\II,<;I; \ss. [ALOPB ' > 



FRACTURE, in Minrralo^y, means the irregular surface wlurh 

 appears when n mineral in brokvn, so that surfaces do not constitute 

 a Cleavage. The kinds of fracture arc determined by the aspect and 

 forms of the surface presented by tho mineral. Werner divide* the 



