M 



UNDULATORY FORCES. LIGHT. 



[LAWS or COMBUSTION. 



importance ventured abroad after dark without hi* i 

 or flambeau. Tlie latt*T, therefore, Iwcame BO india- 

 ponuble to tin- luiilni ;lit ti i\e!I.T. that an ingenious 

 Italian, named I.-iudati. coneeived the idea of opening 

 stalls for thrir hiro. lie started his business in Paris 

 in the month of Mareh, ItM'i 1 .' ; and he managed it go well 

 that he obtained the entire inono]mly of the whole city: 

 his charge for a link was from throe to five sons the 

 quarter of an hour, according to the rank of his cus- 

 r. In liUi7, Nicholas de Reynio, tlie first lieu- 

 tenant-general of police, introduced a still better system 

 of street-lighting. Ho invented lamps of glass, which, 

 from their re<eml>lance to a bucket, were called lantcrnet 

 a tratt. These he fixed in the middle of the streets, 

 exactly in the same way as they are now suspended in 

 many 'parts of France, by means of ropes or wires fixed 

 at each side of the street, the lamp being suspended in 

 the centre. 



We have no means of showing when London was 

 first lighted with lamps ; though Maitland says, in his 

 ry of the Metropolis, that an order was issued as 

 early as the year 1414, commanding the inhabitants to 

 hang out lanterns for the benefit of passers-by. This 

 information is derived from Stow, who, in his purvey of 

 London, remarks that, "in 1417, Sir Henry Barton, the 

 mayor, ordained lanthorns with lights to be hanged out 

 in the winter evenings, betwixt Hallontide and Candle- 

 masse. " It does not appear, however, that these orders 

 were much attended to, for we find that they were 

 repeated again and again over a period of three hundred 

 years. At the expiration of that time the corporation 

 of London determined on removing the service altogether 

 out of the hands of the inhabitants ; they, therefore, 

 entered into contract with a person to set up the public 

 lights, and to attend properly to them ; for which they 

 gave him permission to charge six shillings a-year to 

 every householder whose annual rent exceeded ten 

 pounds. In 1730, the lord mayor and common-council 

 applied to parliament for power to light the streets in a 

 better manner. This power was further increased in 

 1744 ; and, from that time, the illumination of the City 

 has been gradually improving. 



Moat of the preceding facts have been derived from 

 Beckinann, who tells us that the following are the dates 

 when public lamps were introduced into the other cities 

 of Europe : Amsterdam, 16C9 ; Hamburg, 1675 ; Copen- 

 M, 1681; Berlin, 1682; Hanover, 1696; Leipsic, 

 17<r2 ; Vienna, 1704 ; Dresden, 1705 ; Halle, 1728 ; Bir- 

 mingham, 1783 ; Brunswick, 1765 ; Nantes and Ver- 

 sailles, 1777 ; Zurich, 1778 ; and Strasburg in the year 

 following. 



In very recent times the greatest of all improvements 

 in street-lighting has been effected by the use of gas ; 

 and those who can remember the old-fashioned lamp, 

 with its miserable glimmer, and the dangers which con- 

 stantly beset the traveller after nightfall, will have no 

 hesitation in saying that the employment of gas for 

 illuminating purposes has been one of the most important 

 events of modern time. In truth, it has not only been 

 the means of effecting a wonderful change in the whole 

 system of artificial illumination, but it has also produced 

 an equally important change in the domestic concerns of 

 tin' ]>eople : it has encouraged industry, developed the 

 arts, protected property, diminished crime, and operated 

 in a thousand ways as a medium of wealth, prosperity, 

 and social improvement All this has been accomplished 

 in less than half a century ; for Mr. Clegg tells us, in liis 

 work on gas-lighting, that he, in 1813, was the first to 

 put gas into the lamps of Westminster ; and he has also 

 given us a graphic account of the fear and wonder with 

 which it was contemplated. Now, however, it is one of 

 the most familiar objects of daily life ; for there are 

 almost as many gas- lights in this metropolis as there are 

 human individual*. What would Beckmann say of all 

 this, if, in the year 17Kli, he imagined the lighting of 

 London to be perfect, and thought that the appearance 

 of the City, after dark, when seen from a distance, was 

 noble and magnificent ? Of a verity, his admiration 

 would be boundless. One thing, however, is still wanted 



to make gas the greatest boon of the 19th century 

 that is, a guarantee in respect of its purity and harmless 

 qualities. Already the demand fur these has become 

 urgent ; and it will not be long Ix-fure. the gas companies 

 of England will find it to their advantage to yield to it. 

 In fact, the Oity of London has, as usual, taken the 

 initiative in this matter, and has appointed an officer to 

 test the quality of the gas supplied within its boundaries. 

 The results are so important to the community, that all 

 other cities and towns will, ere long, follow ihe example ; 

 and then wo shall hope to see the art of domestic illumi- 

 nation made more perfect than it is at present. 



ON COMBUSTION AND FLAME. 



General Remarks. Artificial light is duo in almost 

 every instance to chemical action that is, to a rapid 

 or energetic union of two or more substanei .,, and the 

 formation of new compounds. At one time it was 

 thought that matter in the act of burning was d- strayed, 

 and thus the term combustion was used to designate the 

 phenomena : but we now know that matter is inde- 

 structible, and that substances, while burning, merely 

 change their form. In proof of this, it may be men- 

 tioned that the chemist is enabled to ascertain the 

 exact composition of an organic substance, by simply 

 collecting and weighing the products of its combustion 

 This, indeed, constitutes the principle of every organic 

 analysis. 



Those substances which evolve light and heat during 

 their chemical union, are generally distinguished by the 

 terms " combustible" and "supporter" the former term 

 being applied to the body which burns, and the latU-r 

 to that which permits of the burning. We speak, for 

 example, of wood, tallow, and coal as combustibles, and 

 of atmospheric air, oxygen, and chlorine as supporters ; 

 but a very little reflection will show that those expres- 

 sions are altogether arbitrary, and that they might in 

 most cases be reversed without destroying their sense. 

 This will be clear from what follows. When coid gas 

 is burnt in atmospheric air or oxygen, we call the gas 

 the combustible, and the air or oxygen tlio supporter ; 

 but by changing this condition of things, and igniting a 

 jet of air in a vessel of coal gas, we should then call the 

 air the combustible, and the gas the supporter; from 

 which it must be evident that the phenomena of c 

 bustion are due to a reciprocal play of affinities, in 

 which one element takes as large a share as the 01 

 and that the distinction of property, as implied by the 

 terms combustible and supporter, is not founded on 

 fact : nevertheless, we still continue to make use of 

 those terms, because of the convenience they afford in 

 description. 



Theories of Combustion. For a long time the phe- 

 nomena of combustion were thought to be dependent 

 on the evolution of a peculiar subtle principle, e 

 jiItlnf/istoH. This hypothesis was originated by Becher 

 in the 17th century, but it was not elaborated until 

 the days of Stahl, when it was universally accepted 

 among chemists as the Phlogistic theory. For more 

 than a hundred years the theory hold a prominent place 

 in the science of chemistry ; and, although it was founded 

 in error, or rather in a total misapprehension of facts, 

 yet its truthfulness was not doubted until the time of 

 Lavoisier, when, by an accurate examination of the 

 facts, he exposed its fallacy. According to the Stahlian 

 theory, there was something namely, phlo 

 always given out during combustion, from which it might 

 reasonably be inferred that the body became lighter ; 

 but, by collecting the burnt products, and weighing 

 them, Lavoisier snowed that it actually became heavier, 

 and that something must, therefore, have been absorbed 

 or taken in. This something he soon found was derived 

 from the atmosphere, and was the gas just then dis- 

 covered by Scheele and Priestly. Having determined 

 these facts, and tested their truthfulness in every pos- 

 sible manner, ho boldly advanced his new theory of 

 combustion, tho Antiphlogistic ; in which he said that 

 the phenomena of combustion wore at all times due to 



