A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. 



' ' To the solid ground 

 Of Nature trusts the mind which builds j or aye." — WORDSWORTH. 



THURSDAY, MAY 3, 1894. 



'HE MODERN 



INCANDESCENT 

 LAMP. 



ELECTRIC 



"he Incanilescent Lamp and its Manufacture. By Gilbert 



S. Ram. (London : Tlie Electrician Printing and 



Publishing Company, Limited.) 

 ^ OW the Swan-Edison monopoly is a thing of 

 the past, the manufacture of incandescent lamps 

 > assuming considerable proportions ; consumers are 

 Iready deluged with applications for orders by con- 

 nental firms, and it is to be hoped that we shall not 

 )ng be obliged to send abroad for what can so easily be 

 lade in our own country. The information in this book 

 i of a unique and valuable nature, and the author seems 

 ) have a thoroughly practical acquaintance with the 

 ubject, and goes into minute details when dealing with 

 11 the different branches of the manufacture. Indeed 

 trade secretism " seems to have been abolished in these 

 ages, and the wealth of technical information here met 

 'ith will go far towards the production of a more efficient 

 imp than those at present in use. 



Chapter i. treats of the filament, and after briefly touch- 



Igon the early efforts to produce lamps with incandescent 



latinum, and the possibilities of making use of some of 



tie metallic oxides, the author passes to the consideration 



carbon filaments now used. It is here noted that 



great improvements may yet be looked for in the carbon 

 self." This is a matter of supreme importance, for the 

 icandescent lamp is as yet in such an early stage of 

 volution as to make it more than probable that the 

 ■idening of the sphere of manufacture will soon bring 

 bout an advance upon its present excellence ; and 



Ithough, as the author points out, the volatilisation of 

 arbon in vacuo will prevent us from attaining to the 

 rightness of the crater of an arc lamp, still there is 

 onsiderable room for improvement. The " electrical 

 olatilisation " or dissociation of particles of carbon from 

 le fdament is noted, and the conclusion is drawn that 



the best carbon is one which at the highest possible 

 jmperature disintegrates at the slowest rate." 

 The value of a lamp from the consumer's point of view 

 NO. 1279, VOL. 50] 



must now be modified, since, by the lowering of the price 

 to IS., the filament can be run at a much higher tempera- 

 ture ; for although the life will be thus reduced, this will 

 be more than compensated by the smaller quantity of 

 current used. 



The materials at present used for the production of 

 carbon filaments— silk, hair, wood fibre, cellulose— are 

 described, and then chapter ii. begins with the practical 

 preparation of filaments. Swan's process for the parch- 

 mentising of cotton thread is taken first, and a good 

 working sketch is given of an apparatus for producing 

 the thread, together with full instructions for the 

 manipulation and drying. Details are also given of the 

 jewelled draw-plates used for bringing down the dried 

 thread to a uniform diameter. This process is the one 

 to which the author devotes most attention. Other 

 processes, such as those in which zinc chloride, furfurol, 

 cuprammonia, pyroxyline and bamboo are used, are 

 mentioned with more brevity. 



Carbonisation is very fully treated of, and excellent 

 drawings are given of frames and blocks for holding the 

 filaments during heating. The furnace is then considered, 

 and a drawing is given of a convenient form of carbonis- 

 ing furnace, the chapter closing with instructions for 

 removing the fragile carbons from their frames. 



Chapter iv. treats of mounting the filaments on their 

 leading-in wires, and after describing the early form of 

 crayon holder used by Swan, the carbon tube of Lane 

 Fox, and the. bolt and nut of Maxim, he passes on to the 

 perfection of all joints— that of deposited carbon. Draw- 

 ings are shown of machines for making this joint, both 

 in the " socket" and "butt" form, and minute instruc- 

 tions are given for depositing the carbon on the junctions, 

 particularly from a liquid hydrocarbon. That recom- 

 mended is a mixture of four parts kerosinc to one part 

 turpentine. 



The next chapter goes thoroughly into the subject of 

 " flashing." Touching briefly on the early days when 

 carbon was deposited on the filament to remedy defects 

 in their uniformity and remove bright spots, the author 

 gives as the reason why it is still necessary to use the 

 process "that the carbon deposited by the flashing pro- 

 cess under certain conditions is much more durable than 

 any that can be produced by any other methods." The 



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