FORM EX. 



FORTIFICATION. 



1M 



FORMEN. [METHTL, J/ydrideof.] 



1). [FORMTL.] 



FORMIC ETHER. (FoRMTL.1 



FORMULAE, CH EMICAL. [CHEMICAL FORMVLJC.] 



FORMYL. This name was originally applied to a hypothetical 



radical (C,H) supposed to be contained in formic acid, chloroform, and 



other bodies, but it is now exclusively used to denote the oxygenous 



radical of formic acid ( r?ur\* V ). This radical is unknown in a 



separate condition, but in combination with oxygen and water it 

 constitutes 



Formic acid, C.HO.HO, which originally obtained its name from 

 having been found present in the red ant (Formica rufa). Hence also 

 the name of the radical fonuyl. This acid may be procured from 

 methylic alcohol, C,H,O + HO, by the loss of two equivalents of 

 hydrogen, and the addition of two of oxygen. It may also be pro- 

 cured by mixing starch or sugar with peroxide of manganese, water, 

 and sulphuric acid, and distilling. It is formed also under a 

 great variety of other circumstances. It unites with lead, forming a 

 formiate of lead, and from this, formiate of soda may be procured by 

 the addition of carbonate of soda. It unites freely with most of the 

 metallic oxides, and many of the salts when heated in closed vessels 



S've off carbonic acid and carbonic oxide, leaving the pure metal, 

 unites also with ammonia, the salt thus formed containing the 

 elements of hydrocyanic acid and water. 



It is the first or lowest member of the important series of FATTY ACIDS. 

 Formyl also enters into the composition of the following compounds : 



(f HO 1 'v 

 ,'u * f<-\J may be obtained by distilling a mix- 

 ture of formic acid and alcohol ; but it is much better procured by 

 Hifa'lling a mixture of 10 parts of concentrated sulphuric acid, 7 of 

 formiate of soda, and 6 of alcohol. The distilled product should be 

 mixed with water to separate the alcohol which it contains, then 

 agitated with magnesia to saturate any excess of acid, and lastly, freed 

 from water by distillation with chloride of calcium. This is Dobe- 

 reiner's process. 



Formic ether is a colourless liquid, of a strong odour, resembling 

 that of peach kernels; its taste is peculiar. Its sp. gr. is 0'915 at 

 65*, and it boils at 132 Fahr. It mixes with alcohol in all pro- 

 portions; but water takes up only Jth of its weight; and after 

 some time the solution is found to be converted into a mixture of 

 alcohol and weak formic acid : this ether burns in the air with a blue 

 flame, the edges and point of which are of a bright yellow. 



Parmobtru&UU acid (C_H,,0 11 ). A composite acid, which stands 

 in the same relation to the benzoic series as lactic acid does to the 

 acetic series. 



Formanilide, Phenyl-formiamide (C 14 H,NO,). One of the products 

 of the action of heat upon oxalate of aniline. [Axn.niKs.] 



FORMYLIA. An organic base so-named by Cloez, but which has 

 since been proved by Hofmann to be ctliyloie-diamine (N,C,H" t H,). 

 It is formed by the action of bi-bromide of ethylene upon ammonia. 



FORNAX (Constellation), the Chemist's Furnace, one of the 

 southern constellations of Lacaille. It is situated immediately below 

 t'etus. It does not contain any stars of conspicuous brightness. 



FORT is the term applied to any enclosed field work, or small 

 permanent work. It is however often very loosely applied. 



FORTE (Italian strong, loud), a musical term, directing the per- 

 former to sing or play loudly, with strength. 



Portunmo is the superlative of Forte. 



FORTRESS, a fortified city or town, the works of which are such as 

 to require an attack in form, or are capable of resisting an attack de 

 vive force. 



FORTIFICATION is the art of constructing works for the protec- 

 tion of a town or military position ; the object being to enable a lesser 

 force to be a match for a greater from the advantages of its position. 

 Or, as in the case of offensive fortification, such as siege works, to 

 increase the power of the assailants. Fortification has, therefore, been 

 divided into two parts, jirrmaaent and field, the former comprising 

 such works as are intended to last for many years, and the latter such 

 as are hastily executed for the defence of a position of an army in the 

 field, or the attack of a fortress. 



The principles which regulate the general plan of the works con- 



towers projecting from it at intervals towards the front ; and a barba- 

 can, or outwork, consisting of two or more towers, connected by walls 

 like those of the fortress itself, was generally constructed on the 

 exterior side of the ditch and opposite a gate of the town, in order to 

 protect that entrance and the bridge leading to it. The towers and 

 walls about an ancient town correspond to the bastions and curtains 

 funning the enceinte of a modern fortress, and the barbacan may be 

 considered as the counterpart of its ravelin, or principal outwork. 



The necessity which the nations of Europe were under of remodelling 

 their fortified towns in consequence of the change produced in the art 

 of war by the invention of gunpowder, gave occasions for the engineers 

 if Italy, France, and the Netherlands to emulate each other in de- 

 vising the most advantageous methods of disposing the works for the 



purposra of defence with relation to the arms then newly introduced ; 

 and the result of their labours ws the construction of numerous 

 strong fortresses on the frontiers of those countries. In these the 

 bastion system, as it is called, was invariably adopted [BASTION] ; and 

 it is remarkable that, of the very numerous projects which have been 

 offered to the world for fortifying places, so few should have been till 

 latterly of a different kind. The variations however which occurred 

 in the details of the plans gave rise to the denominations of the 

 Italian, the French, the Spanish, and the Dutch methods, in speaking 

 of the works proposed or executed at the end of the 16th and the 

 beginning of the 17th centuries ; but it must be observed that those 

 variations consisted chiefly in the magnitude of the angle v. hi. h tin- 

 two faces of a bastion made with each other, and in the extent of what 

 was called the second flank ; that is, the portion of the curtain then 

 generally left between the flank of a bastion and the place where the 

 produced face of the collateral bastion intersected the curtain. 



The first bastioned fortresses of France appear to have been very 

 inferior to those which were executed in the Netherlands by the 

 Italian engineers ; and there still exist some remains of these last in 

 which the bastions are sufficiently capacious, and at distances from 

 each other within the effective range of musket-shot. The others, on 

 the contrary, were characterised by small bastions, scarcely capable of 

 receiving artillery, and placed so far asunder as to defend each other 

 very imperfectly. But after the termination of the civil wars which 

 desolated the country, the attention of the French government was 

 directed to the state of the military posts ; and Krrard de Bar le Due, 

 a member of the corps of engineers then instituted, was appointed to 

 superintend the reparation of the old, and the construction of the new 

 fortifications. The citadel of Amiens was built according to the plan 

 proposed by this officer, who, in 1594, published a treatise on fortifica- 

 tion, in which some effort is made to determine the principles which 

 should regulate the forms and dimensions of the works ; his method, 

 however, is only a faulty modification of the Italian. 



In the method proposed by Errard the bastions are much larger 

 than those of the earlier time, the length of their faces being, as at 

 present, about one-third of the distance between the salient angles of 

 two collateral bastions; an orillon occupied nearly two-thirds of the' 

 length of each flank, which was very short, and formed an angle of 

 about 80* with the curtain. This direction appears to have been 

 given to the flanks in order that the guns behind their parapets might 

 be as much as possible concealed from the view of the enemy in his 

 counter-battery ; but it is evident that the defenders of the opposite 

 flanks, laying their muskets perpendicularly to the lengths of the 

 parapets, according to the general practice, would almost inevitably, 

 especially in the dark, fire upon each other, or upon those who were 

 stationed on the curtain. 



De Ville, who composed a treatise on fortification in 1629, made 

 several improvement*) on the method proposed by Errard, the prim ijl 

 of which were an augmentation of the length of the flanka and a |T- 

 pendicular direction of the latter with respect to the curtain : by these 

 changes a better defence was obtained from the flanks, and tl 

 above mentioned was diminished. But a still greater amelioration was 

 made by Count Pagan, who, in 1645, proposed to make each flank [see 

 the half-front of Fortification between F and a, fig. 1, BASTION] per- 

 pendicular to the produced face of the collateral bastion ; the reciprocal 

 defence which the works should afford each other is thus complete, and 

 the men are not in danger of being fired on by each other. Pagan 

 retains the orillons at the shoulders of the bastions, and he gives to 

 the latter double or triple flanks ; but the construction of these, and 

 of many other works supposed to be modern improvements, such as 

 the demi-revetment, are to be found in Castriotto's work, published in 

 Venice in 1564 : they have, however, on account of their numerous 

 inconveniences, ever since been discontinued. 



During the reign of Louis XIV. a general reparation or recon- 

 struction of its fortresses was ordered by the French government ; and 

 the talents of Vauban, which were exercised in devising and carrying 

 into execution, the strengthening and improving 300 places and the 

 building of 33 new ones, together with the merit displayed in tin- 

 conduct of fifty-three sieges, have given that engineer so much celebrity. 

 Besides the changes made in the disposition of the parts of the enceinte, 

 the outworks were entirely remodelled ; and instead of assigning for 

 the delineation of the plan, numerous arbitrary rules which varied 

 with the nature of the polygon, Vauban adopted the length of the 

 side of the |>olygon as a base, and took certain aliquot parts of this 

 line for the dimensions of the several divisions of the ramjiart ; thus 

 reducing the construction to a few simple precepts wlikh weir appli 

 cable to places of all magnitudes. These precepts being founded on 

 the uses of the works may be justly considered as constituting a 

 system of fortification, though many of his works are found in older 

 writers; and from that time to the present scarcely any deviations 

 have been made from them in the construction of great fortresses. A 

 brief outline of the system will therefore be here given. [See the half- 

 front of fortification between a and K,fig. I, BASTION.] 



The length of each side, as F E, of a regular polygon supposed to 

 surround the town or position, is made from 320 to 400 yards, say 

 about 380 yards, in order that all the parts of the nunpai t on each 

 front of the enceinte might be within the range of the arms employed 

 in the defence, but more especially that the faces of the bastions 



