461 



BURNERS. 



BURNS AND SCALDS. 



are made of thin strips of bamboo, woven like fine basket-work. After 

 the first coat of varnish, the interstices are filled up with a paste made 

 of wood-oil mixed with different fine powders, such as calcined bone, or 

 sawdust from teak-wood. After the paste has been smoothed by the 

 hand, the cup is laid aside to harden in a cool place ; when sufficiently 

 hardened, the surface is smoothed with pumice-stone and water. The 

 cups are afterwards varnished three or four times, and polished by 

 rubbing. The varnish mostly used in India and Burmah, under the 

 name of wood-oil, is obtained by incision from the Dipterocarfnts 

 "tttts, and a few other trees. In the Burmese ware this varnish 

 is not laid on with a brush, but by the hand, in order to preserve a fine 

 surface, and to enable the workman to discover and remove any particles 

 of dirt. When first laid on, the varnish appears of a light brown 

 colour, which is changed to a fine black by rubbing with the hand. 

 The varnished and polished cups are kept in a cold vault for three 

 days, to harden the varnish. Sometimes the cups are ornamented with 

 raised figures ; these are made of the game paste that is used to fill 

 up the interstices of the basket-work. The paste is pressed into tin 

 moulds, and afterwards transferred to the cups or bowls ; when dry, it 

 becomes as hard and solid as wood. Occasionally the cups are orna- 

 mented with engraved designs, which are afterwards filled up with 

 different-coloured powders, mixed with wood-oil ; the surface is then 

 smoothed with wet bran, held in the hollow of the hand. The opera- 

 tion is repeated, to ensure the complete filling up of all the lines ; and 

 the cups are finally varnished and polished as usual. 



BURNERS. [AKGAND; GAS LIGHTING ; LIGHTS, ARTIFICIAL.] 

 BURNING. [ARSON; BRAND.] 



BURNING GLASSES and MIRRORS. Any lens of the convex 

 kind, or mirror of the concave kind, which collects a quantity of light 

 within a very small space, will, if the light be very strong, such as that 

 of the sun, also collect a considerable quantity of heat, which will set 

 fire to many substances ; or, if the glass have an aperture of some size, 

 almost any sub stance whatsoever. This property has buen long known. 

 The last proposition of the treatise on catoptrics attributed to Euclid 

 is, " By concave mirrors placed opposite to the sun, fire may be 

 kindled ; " and the reason is explained, namely, the condensation of the 

 sun's rays. In the'Cloudi' of Aristophanes (766, &c.), Strepsiades 

 tells Socrates that he has found out an excellent way of cancelling his 

 debta, namely, by standing at a distance from the 'awyer who is 

 drawing up the case against him, and destroying the writing by 

 catching the sun's rays in such a burning-glass or transparent stone as 

 people kindle fire with. We may see under ARCHIMEDES [BiOG. Div.] 

 that the stories relative to his burning the Roman fleet by mirrors are 

 of comparatively modern authority. From the end of the 17th 

 century various experiments have been made with glasses of con- 

 sidi Table power ; but as no important results followed, beyond the 

 e.-itaulishnient of the great effect which may thus be produced, the 

 subject has become of little importance, especially, as when high 

 temperatures are required, the oxy-hydrogen blowpipe, or the voltaic 

 battery is at the command of the chemist. We shall, however (refer- 

 ring the reader to LI:NS and MIRROR for all stricter notions upon the 

 subject), state some facts connected with burning glasses in a more 

 popular shape. 



It is found that heat alone without light passes very slowly through 

 glass ; that even with ordinary light very little heat is transmitted 

 through glass ; and that it is only with the full glare of sun-light that 

 any sensible effect can be produced. If a convex lens be held directly 

 opposite to the sun, and allowed to throw an image on a sheet of 

 paper held behind and parallel to it, and if the sheet of paper be 

 moved until the image of the sun thrown upon it appear smallest, the 

 quantity of light transmitted through the glass, which remains the 

 same (hroughout, is then thrown upon the smallest quantity of surface, 

 and presents the greatest condensation of light and heat which the 

 gloss will afford. The same phenomenon would be perceived in a 

 concave mirror, with this defect, that the surface which is held before 

 it must intercept a part of the light. 



Two glasses were made by Tschirnhausen, before 1699, which are 

 among the earliest of the attempts to produce considerable effects ; the 

 first of 33 inches diameter and 7 feet focal length, the second of the 

 nine diameter and 12 feet focal length (old Parisian measure). A 

 second lens received the rays and diminished the focal distance. The 

 effect was to burn small portions of wood, or boil water, also in sma,ll 

 quantities, in one moment ; to melt small pieces of metal, to vitrefy 

 slate, tc. ; to melt pitch and resins under water. But the most 

 complete effect was produced from a lens made by M. de Trudaine, 

 about 1774, which did not consist of glass alone, but was a hollow lens 

 of ^lass, filled first with spirits of wine, which was afterwards changed 

 for terebinthine oil. It held 140 pints (Parisian), and filled with the 

 latter substance had about eleven feet of focal length. According to 

 M. Brisson (afterwards cited), who made the experiments, a bar of 

 steel, four inch' s long and a third of an inch square (Parisian), was 

 completely melted in five minutes. A silver coin of three livres was 

 melted in a few fwcond.i, and <>n<- of six livres in nearly the same time ; 

 grains of platinum were sufficiently melted to cohere, though not to 

 form a spherical drop. 



M. Bulfon, remembering the story about Archimedes, endeavoured 

 to form mirrors which should burn at a ^ruat distance. The dis- 

 advantage of trying to gain power by increasing the aperture lies in the 



great relative increase which is thereby given to the small image of 

 the sun. No spherical, glass or mirror refracts or reflects rays accu- 

 rately to a point. The plan of M. Buffon was to make his mirror 

 consist of a large number of small plane mirrors, 400 in number, so 

 placed that they should all reflect their several images of the sun on 

 the same point. He thus burnt wood at 200 (French) feet distance, 

 melted tin at 150 feet, and lead at 140 feet. 



The only practical application of the burning glass (if it deserves so 

 dignified a name) of which we ever heard, is the following : A burning 

 glass is placed in such a way that the sun shall throw its image into 

 the touch-hole of a small cannon, at its greatest height, which thus 

 explodes within a minute or two of noon, if there should happen to be 

 no cloud in the way. 



BURNS AND SCALDS. Burns are produced by heated solids; 

 scalds by heated fluids. The severity of the injury is dependent 

 mainly on the intensity of the heat of the burning body. Fluids are 

 not capable of acquiring so high a degree of temperature as some 

 solids; hence the immediate effect of scalds is generally less violent 

 than that of burns. But, on the other hand, fluids flow about with 

 great facility, and the accident often causes a very large surface of the 

 fluid to be thrown upon the body, so that a scald which produces only 

 a moderate degree of inflammation sometimes becomes exceedingly 

 severe on account of its extent. As heated fluids part with their 

 caloric in being diffused, a scald is almost always attended with a 

 different degree of injury in different parts of its course. The extent 

 of the surface involved, the depth of the injury, and the sensibility of 

 the part affected, must all be taken into account in estimating the 

 danger of the accident in any given case. A burn which produces 

 the instantaneous death of the part it touches may be free from all 

 danger if the injured part be circumscribed within a small compass. 

 The worst burns which occur arise from the explosion of gunpowder, 

 or of inflammable gases, or from the female dress catching fire ; and 

 the worst scalds from the boiling over of heated fluids in breweries, 

 manufactories, laboratories, &c. 



The immediate seat of the injury produced by burns and scalds is 

 the skin, which is a highly organised membrane, performing a very 

 important organic function, and endowed with a high degree of sensi- 

 bility. [SKIN, NAT. HIST. Div.] The organic function performed by 

 it is the secretion of a quantity of aqueous fluid from the blood, which 

 is carried out of the system under the form of perspiration. The 

 secretory arteries of the skin are excited to such an unusual degree of 

 action by the stimulus of the heated body, that they pour out an 

 aqueous fluid in such quantity as to lift the cuticle from the cutis or 

 true skin, and form a vesicle or bladder full of fluid. Such is the 

 violence done to the true skin, that the function of all the injured 

 portion of it is suspended ; additional labour must therefore be im- 

 posed on some other organ, which must be its substitute and perform 

 its work, otherwise a fatal disturbance will take place in the system. 

 The lung exhales the same aqueous fluid as the skin. [LUNGS, NAT. 

 HIST. Div.] In proportion as the cutaneous perspiration is diminished, 

 the pulmonary transpiration is increased ; but when a large extent of 

 the skin is destroyed, the lung is inadequate to the task imposed upon 

 it ; it cannot perform its own work and that of the skin also, and in 

 this case great difficulty of breathing invariably comes on, and the 

 danger is exceedingly increased by this oppression of the lung. 



But there is spread over the external surface of the true skin an 

 immense number of sentient nerves, rendering it an organ of sense. 

 A burning body applied in such direct contact with the sensitive 

 extremities of these nerves occasions violent pain ; and this, in conse- 

 quence of the sympathy which is established between all parts of the 

 body, produces a great disturbance of the system. The abolition of 

 the organic function, and the disturbance occasioned to the sentient 

 part of the nervous system, both combined, often prove fatal. 



Since the severity of the injury must always be mainly in proportion 

 to the length of time the burning body continues in contact with the 

 skin, it is important that every one should impress upon his mind the 

 course which it is best to take in case of accidents from burns. 



The upright posture is obviously not only favourable to the spread- 

 ing of the flames, but to their reaching the more important parts of 

 the body, the neck and head. Any motion of the body to and fro 

 gives great advantage to the flames, by bringing fresh currents of air 

 into contact with the burning materials, and it is therefore utterly 

 absurd to run screaming about. Fall upon the floor ; keep rolling 

 over and over upon the carpet : if possible seize the hearth-rug, or the 

 table-cover, and, enveloping the body in it, keep rolling about upon 

 the carpet until assistance comes. The duty of the assistant is to seize 

 the hearth-rug, or the table-cover, or a shawl, or to strip himself of 

 his coat, or to seize any woollen or flannel clothing at hand and to 

 envelope in it as closely and completely as possible the person on fire. 



The thing to be done with the burnt or scalded parts is instantly to 

 immerse them in cold water, ice-cold if it can be got. Should the 

 position of the parts not allow of their immersion in water, cloths 

 should be applied to them dipped in water, and kept constantly wet. 

 As a means of applying and retaining cold, scraped potatoes or turni|>3 

 are useful. Some persons recommend, instead of those cooling appli- 

 cations, stimulating substances, such as the strongest brandy, spirits of 

 wine-, oil of turpentine!, or vinegar, kept on the affected parts, by means 

 of old luien or lint soaked in the fluid. The use of these applications, 



