297 



LINES OF INTRENCHMENT. 



LINUM USITATISSIMUM. 



298 



during his advance ; on a level plain however the longer branches 

 would be subject to the serious defect of being easily enfiladed. The 



distances between the salient points b, d, &c., should not exceed 100 

 yards, and the lengths of the short branches may be about 18 or 20 



yards. The re-entering angles a, e, &c., should contain about 100 

 degrees ; and the entrances are usually placed at those points. 



A like construction may be adopted when it is required to corinect 

 two points, as M and u, by a line along a narrow and elevated ridge of 

 ground ; and in this case the directions of the branches 6 c, d e, &c., 

 may change in the middle of the line, as shown in the figure, in order 

 that the fire from the long branches may be directed to the front of 

 the nearest works, as M and N, in which it is to be supposed that 

 artillery would be placed for the purpose of defending the ground 

 before the intermediate line. 



It may be added also, that the line A crtmailltires (indented line) 

 is convenient when it is required to join forts on hills or rising 

 ground. 



The most perfect fortification for defending a line of country pre- 

 senting few natural obstacles to the advance of an enemy, should the 

 importance of the position render it advisable to incur the labour of 

 the construction, would be a series of bastions connected by curtains, 

 either straight or broken. The principles on which the several fronts 

 of fortification should be formed correspond to those adopted for 

 regular fortresses, which are described in the article FORTIFICATION ; 

 the only difference being in the lengths of the several parts. These 

 depend upon the whole length of the front, which here should not 

 exceed 180 yards, that the ditches of the bastions may be well defended 

 by common muskets from the collateral flanks. Neither ravelin nor 

 covered-way would of course be necessary. 



Lines of intrenchment composed of works placed at intervals from 

 one another, provided the distances be not so great as to prevent the 

 troops in them from mutually assisting each other, have great ad- 

 vantages over those formed of continuous lines of parapet. In the 

 latter case it is scarcely possible for the army to make a movement 

 for the purpose of attacking the enemy however favourable the oppor- 

 tunity, since much tune would be lost in issuing from the line through 

 the narrow passages ; and as these are the objects against which the 

 fires from the enemy's batteries would then be incessantly directed, 

 it would be almost impossible to form any extended front for attack ; 

 besides which, the enemy penetrating at any one point the whole line 

 is turned. Detached works, on the other hand, constitute a number of 

 strong points by which the position of the army is secured; while 

 through the spacious intervals an advance or retreat may take place 

 with the utmost facility. Their artillery is conveniently situated for 

 putting the enemy's line in disorder previously to the attack, and for 

 protecting the retiring columns in the event of their quitting the field. 

 It may be added that detached works are capable of being easily 

 adapted to any kind of ground ; for it is merely necessary to place 

 them on the more elevated spots in such situations that the enemy 

 may not be able to penetrate between them without being exposed to 

 their fire. 



On level ground the intrenchment may consist of a number of 

 redans, as A, B, c, with or without flanks, disposed on a right line or 

 curve, and at distances from one another equal to about 300 yards, 



Fig. 3. 



A 



<*> 



that the fire of musketry from them may defend the intervals. In the 

 rear, and opposite the intervals between the works in the first line, a 

 second line of works, as D, K, should be formed; and the faces of these 

 should be disposed so as to flank the ditches and approaches to the 

 others. The gorges of the exterior works should be open, as in the 

 figure, or only protected by a line of palisades, which, in the event of 

 the enemy gaining possession of those works, might be destroyed by 

 the artillery in the second line. 



Instead of a series of redoubts forming an interior line, it may 



ffice, should the works A, B, c, &c., be disposed on a convex arc to 



i one large central redoubt as F, so situated as by its artillery to 



defend both the intervals between the redans and the ground within 

 their line. 



All the works which have been described consist of parapets formed 

 of earth obtained by cutting a ditch in front ; and the profile of any 

 one work with its ditch is shown in the subjoined figure (4). 



The elevation of the crest A above the natural ground is about 7i 

 feet, unless the vicinity of a commanding height in front should render 

 a greater relief necessary, and the depth of the ditch may be the same. 

 The thickness A a of the upper part of the parapet is variable, and 

 depends upon the importance of the work, or rather, upon the arm 

 which may be employed in the attack : if it were required only to 

 resist a fire of musketry, 3 feet would suffice ; but from 8 feet to 12 

 feet would be necessary in the event of artillery being brought against 

 it. (Twelve-pounder shot is the heaviest which the French have ever 

 yet employed in the field.) The form of the parapet is the same as in 

 permanent fortification ; when time permits, the exterior and interior 

 slopes should be reveted with sods, and a line of palisades should be 

 planted along the foot of the counterscarp. 



LIXIN, a crystalline substance of unknown composition found in 

 the mountain flax (Linum catharticum). 



LINOLEIC ACID. [OLEIC ACID.] 



LINOLEIN. [OLEIC ACID.] 



LINSEED (Graine de Lin, French ; Leinsaat, German ; Lynzaad, 

 Dutch ; Linaza, Spanish ; Linhaca, Portugal ; Linseme, Italian ; Sem- 

 jalenjanve, Russian), the seed of the Lin, Linum, or flax plant, is a 

 valuable product derived from the capsules of Linum usitalissimum, 

 and consisting of small grayish-brown lenticular bodies, containing a 

 mealy albumen, of so oleaginous a nature, that it yields by pressure in 

 great abundance the oil of linseed. The seed of the flax-plant is 

 harvested not merely with a view to the reproduction of the plant, 

 but also because of the oil which it yields by compression. For both 

 these purposes, of sowing and crushing, linseed is largely imported 

 into the United Kingdom. [LIKEN MANUFACTURE; FLAX.] It is 

 largely used now as cattle food and the refuse, after its oil has been 

 expressed, is the well-known oilcake of the cattle feeder. 



LINSEED-OIL may be procured by cold expression of the seeds, a 

 process which makes the oil clearer ; or the bruised seeds are roasted 

 in the oil-mills, in which case it is brownish-yellow, and easily becomes 

 rancid, probably from attracting oxygen. Linseed-oil is pellucid, 

 with a faint but peculiar odour and taste, generally disagreeable' 

 from being subrancid. Specific gravity 0'93. It easily dries : by 

 reduction of temperature it merely becomes cloudy, but scarcely 

 freezes. 



It may easily be purified by repeated agitation with water, by 

 bleaching in the sun, or, better, by filtering it through newly prepared 

 charcoal. 



By long boiling it becomes dark-brown, tenacious, and thickened, 

 but dries more easily, and in this state is used for printers' ink ; by 

 still longer boiling it becomes black, almost solid, and elastically 

 tenacious, like caoutchouc, and in this state it serves for bird-lime. 



By the addition of nitrous acid it becomes thick and red, then dark 

 reddish brown, like tincture of iodine, but does not become solid. It 

 is frequently adulterated with rape oil, which may be detected by this 

 test. Neither does it form elaidin, as rape-oil does. But a simpler 

 test is, that if wood be smeared with oil which has been adulterated it 

 does not become dry. 



Linseed-oil is used to form liniments, of which the most common is 

 that with lime-water, as an application to burns. But it is much 

 more extensively used in the arts, particularly for painting. It is 

 mildly laxative. 



LINT. [LINUM USITATISSIMUM.] 



LINUM USITATISSIMUM, Medical Properties of. The seeds of 

 this plant yield several articles useful in medicine and surgery. The 

 testa, or husk of the seeds, is very mucilaginous, the kernel contains 

 much oil, and the farina or meal, procured by grinding or bruising the 

 seeds, after the oil has been expressed, furnishes an excellent material 

 for poultices, but now greatly superseded by Spongiopiline. [CATA- 

 PLASMS.] The seeds are oblong-ovate, acute, compressed, brown, 

 shining, very smooth, the skin thin, the kernel white and oily. They 

 are devoid of odour, but have an unpleasant mucilaginous oily taste. 

 Old, rancid, and corroded seeds should be rejected. One part of seeds 

 and two parts of water yield a strong mucilagei It is much better to 



