217 



BLINDAGE. 



BLISTER. 



218 



receive payment. He returned with the account and the mattress too. 

 ' I've brought baith back, ye see, sir,' said he. ' How so ? ' ' Indeed, 

 sir, I didna like t'leave't yonder, else I'm sure we wad ne'er see the 

 siller there's no a stick of furnitur' within the door ! ' ' How do you 

 come to know that ? ' ' Oh, sir, twa taps on the floor wi' my stick 

 soon tell't me that ! ' Having to send the same man to Portobello, 

 toward evening, I warned him (rather inadvertently !) that if he did 

 not make haste it would get dark. ' My word, sir,' said he laughing, 

 ' I wish I had a shillin' for ilka time I've been in Portobello i' the 

 dark.' 



" As a body, the blind are the most habitually cheerful of mankind. 

 How it comes to be so I cannot tell, and I have no wish to theorise. 

 I cannot designate the blind, as is almost universally done, ' the un- 

 happy,' . ' melancholy,' ' pitiable,' and so on. I know nothing more 

 erroneous, or more opposed to the feelings of by far the greater 

 majority." So says Mr. Anderson in his 'Observations on the 

 Employment, Education, and Habits of the Blind,' and he was a man 

 of large experience among them. 



BLINDAGE (called also BLIND), is a term employed in military 

 art to any temporary construction made to secure artillery against the 

 effects of ricochet and vertical fire, or the troops against the effects of 

 shells ; it consists usually of stout timbers, covered with fascines, 

 earth, and sodwork, and in fact is the temporary expedient for 

 casemates. 



In fortresses, when regular casemates have not been constructed for 

 the protection of the ammunition and provisions, or of the soldiers 

 while not employed in active duty, covered buildings of a temporary 

 nature are formed for those purposes at, or previously to,- the com- 

 mencement of a siege. The simplest are such as are made against the 

 side of some strong wall within the place, or, which is preferable, 

 against the revetment of the counterscarp, in a dry ditch, on any of the 

 fronts not exposed to the fire of the enemy. These inclined blindages 

 consist, when timber is plentiful, of thick beams placed close together, 

 and leaning against the wall at an angle of 45, one extremity of each 

 resting on a sleeper laid in the ground : in other cases the beams are 

 placed at intervals from each other ; over them are laid horizontal 

 joists close together, and the whole is covered to the required thickness 

 with fascines^nd sods when they can be procured ; the entrance is at 

 one extremity of the building. This kind of blindage is also con- 

 structed to cover the miner employed in piercing the escarp wall of a 

 rampart when the breach is to be formed in it by the explosion of 

 a mine. 



A blindage is sometimes formed independently of any wall, by 

 planting the timbers in the ground in inclined positions so that their 

 upper extremities meet together in a ridge, when the building 

 resembles the roof of a house, and the whole is covered with fascines 

 and sods. But generally an area is enclosed by a wall made of strong 

 palisades planted vertically in the ground, the roof being formed of 

 timbers disposed horizontally and close together, above which comes 

 the bed of fascines and earth. For a small magazine the inclosing wall 

 may consist merely of gabions filled with earth ; the area being covered 

 as before. 



A blindage is said to be bomb-proof, when, from the thickness of its 

 roof, it is capable of resisting the shock of loaded shells ; and splinter 

 proof when merely capable of securing persons within it against the 

 fragments resulting from the explosion of such shells. 



The French give the name of blindage to any building already 

 existing in a fortress, when a shell-proof covering has been made to it 

 in place of its proper roof ; this cover is obtained by placing girders 

 lie ulterior, and overlaying them with joists and earth. And 

 when the walls are not sufficiently strong they should be cut down to 

 a convenient height, and covered as before. On the exterior of the 

 building leaning blindages may be formed as above described, and 

 sometimes the whole of the exterior walls are protected in the same 

 manner, leaving only the entrances, which are generally opposite to the 

 piers between the doors and windows, where some of the inclined 

 timbers are omitted : but occasionally the walls and roof are merely 

 strengthened and supported by shears or inclined props firmly fixed 

 below in the ground, and above resting against and supporting the 

 extremities of the girders. For these kind of blindages such buildings 

 should be selected as have their lengths in the probable direction of 

 the enemy's fire, to avoid as much as possible their being exposed to 

 direct fire. 



To secure some of the artillery on the ramparts of a fortress against 

 the effect* of ricochet and vertical fire, shell-proof blindages are formed, 

 by planting in the earth strong palisades vertically six feet on each 

 aide of the gun, extending from the interior slope of the parapet about 

 24 feet to the rear, across the terreplein or upper surface of the 

 rampart; these carry a roof made with timbers, which extending 

 forwards covers the embrasure as far as 9 or 10 feet from its neck, or 

 interior extremity. These blindages are open towards the rear, and 

 the guns fire through the embrasures as usual. The under side of the 

 timbers of the roof is about 7 feet above the terreplein, and is 

 covered with a double layer of fascines and earth above that to a thick- 

 ness of about 5 feet. It has also been recommended to form the 

 blindage in the thickness of the parapet itself, the roof being well 

 covered with timbers, fascines, and earth, open to the rear, but the 

 exterior closed by a number of stout timbers placed horizontally, so as 



to make a wall 4 feet thick, through which the embrasures are cut, 

 like the portholes of a ship. 



In the attack of fortresses, when the trenches of the besiegers 

 become subject to a plunging fire from the place, they are protected 

 by blindages ; these are formed by fixing rectangular frames of timber, 

 commonly called great gallery frames [MINES], vertically along the 

 two sides of the trench, and placing similar frames or any timbers 

 across the trench on the top of these, to carry the roof which consists 

 of fascines covered with earth or raw hides. 



Blinded trenches of this kind were formerly much used by the 

 besiegers to protect their descent into the ditches of fortified towns ; 

 one of this kind was executed by the French for that purpose when 

 they besieged Danzig in 1813. 



BLINDNESS. [EYE.] 



BLISTER, a term used to express a bladder or vesicle raised upon the 

 skin by the application of some external irritating substance, and also 

 to denote the external application itself by which this effect is produced. 

 The terms vesicatory and epispastics are also frequently given to the 

 external application or other preparation. The substance usually 

 employed as a vesicatory is the powder of the Spanish fly. [CANTHA- 

 RIDES.] The powder of the eautharides is mixed with lard and wax, 

 so as to produce a plaster of tolerably firm consistence, which is spread 

 on leather and applied to the part for the space generally of from ten to 

 twelve hours. The first effect of the application of the blister-plaster 

 to the external skin is to produce a sense of tingling and heat ; this is 

 followed by redness, commonly attended with pain, and subsequently 

 there takes place an elevation of the cuticle into a vesicle or bladder, 

 which contains a fluid resembling the serum of the blood. On the 

 effusion of this fluid the redness continues for some time ; the serum 

 gradually thickens, and at last is changed into a whitish curdly sub- 

 stance, under which new cuticle is formed, though occasionally the 

 serum is converted into proper purulent matter, the blistered part 

 successively contracting, until the whole wound is healed. Sometimes 

 coagulable lymph is effused. 



The effect of the application of a blister is the production of a true 

 inflammation over the whole surface of the skin with which the 

 plaster is in contact. The effusion of a serous fluid from the excited 

 capillary vessels of the skin is one of the ordinary phenomena of 

 inflammation. The formation of the bladder or vesicle is occasioned 

 simply by the elevation of the cuticle from the true skin, by the fluid 

 poured out from the cutaneous capillary vessels. The inflammation 

 induced by the blister is the effect of a powerful stimulus applied to 

 the cutaneous blood-vessels and nerves. 



The extent of the inflammation is usually confined to the surface in 

 actual contact with the blister ; it is comparatively rare that any 

 degree of irritation is communicated to the general system ; and yet 

 the relief afforded is often so great, that the effect appears dispro- 

 portioned to the cause, a small external inflammation mitigating or 

 removing an extensive and severe internal inflammation. Much dis- 

 cussion has taken place as to the principle on which this relief is 

 afforded, and the real mode in which the blister produces the benefit 

 observed to result from it is not clearly understood. It is certain that 

 the chief benefit results in the state of what is termed local inflamma- 

 tion ; that is, when the inflammatory action is confined to a single 

 organ or to a part of an organ. In order to understand the true 

 nature of the change effected in the part relieved, it is obviously neces- 

 sary to understand the true nature of inflammation. [INFLAMMATION.] 

 It may be here stated, that in inflammation artificially induced with a 

 view of observing the phenomena that take place in this process, the 

 blood-vessels of the part inflamed are seen to enlarge and to become 

 preternaturally distended with blood, while the motion of the blood 

 in such vessels is either very much retarded or ceases altogether. The 

 knowledge of this fact enables us to understand, in some measure, the 

 action of a blister. The application of a powerful stimulus, such as 

 that caused by the Spanish fly, in the neighbourhood of vessels relaxed 

 and over-distended with blood, relieves such vessels by depriving them 

 of a portion of their blood, and by consequently removing the state of 

 over-distention. For the stimulus applied to the skin determines a 

 large quantity of blood to the cutaneous vessels under the influence of 

 the vesicatory ; this blood is derived from the blood-vessels of the 

 parts in the immediate neighbourhood of the vesicated skin, from the 

 blood-vessels of the inflamed part among the rest ; and the blood- 

 vessels of the inflamed part being relieved from the preternatural 

 quantity of blood that distended them, return to their healthy action. 



Another reason has also been assigned for the relief afforded by the 

 application of blisters. It is observed, that when a morbid action 

 exists in any part of the body, it may sometimes be removed by 

 exciting a morbid action of a different kind in the same or in a neigh- 

 bouring part. It is assumed that two morbid actions of different kinds 

 cannot go on in the same part at the same time ; hence the surgeon 

 and physician, when they observe diseased action going on in a par- 

 ticular part of the body, induce, as near to that part as possible, 

 another action of a different kind, frequently with the effect of lessen- 

 ing or altogether stopping the former morbid action. Now one of the 

 instruments most commonly employed to excite this new action is the 

 blister, and the excitement of such action, on the principle just stated, 

 is conceived to be one mode in which the blister, as a general remedy, 

 proves beneficial. 



