NATURE 



341 



THURSDAY, FEBRUARY 12, 1880 



EDISON AND THE ELECTRIC LIGHT 



MR. EDISON has once more come forward with an 

 electric lamp, which we are assured solves the 

 problem of the economic subdivision of the electric light. 

 We have heard this statement so many times with respect 

 to one form or other of lamp devised by this most 

 ingenious ai>d indefatigable inventor, each of which in 

 turn has come to no tangible result, that it becomes 

 harder than ever to trust to the rash announcements 

 flourished so airily by the newspaper press on both sides 

 of the Atlantic. 



What is then the nature of the inventions thus heralded 

 before the world ? Regarded quietly, and without pre- 

 judice, from a scientific standpoint, what is the value of 

 the dis:overies which can thus play havoc on the Stock 

 Exchange ? 



A recent number of the New York Herald contained a 

 long and detailed history of Edison's experiments on 

 electric lighting, from which the following description of 

 the new lamp is taken : — 



"With a suitable punch there is cut from a piece of 

 ' Bristol ' cardboard a ^trip of the same in the form of a 

 miniature horseshoe, about two inches in length and one- 

 eighth of an inch in width. A number of these strips are 

 laid flatwise in a wrought iron mould about the size of the 

 hand and separated from each other by tissue paper. 

 The mould is tht-n covered and placed in an oven, where 

 it is gradually raised to a temperature of about six hundred 

 degrees Fahrenheit. This allows the volatile portions of 

 the paper to pa-s away. The mould is then placed in a 

 furnace and heated almost to a white heat, and then 

 removed and allowed to cool gradually. On opening the 

 mould the charred remains of the little horseshoe card- 

 board are found. It {sic) must be taken out with the greatest 

 care, else it will fall to pieces. After being removed from 

 the mould it is placed in a little globe and attached to the 

 wires leading to the generating machine. The globe is 

 then connected with an air-pump, and the latter is at 

 once set to work extracting the air. After the air has 

 been extracted the globe is sealed, and the lamp is 

 ready for use. . . . The entire cost of constructing 

 them is not more than twenty-five cents." 



Since the date of this article a paper has been published 

 in Scribmr's Monthly Magazine for February, written by 

 Mr. Upton (" Mr. Edison's mathematician") but attested 

 by Mr. Edison's signature as the " first correct and 

 authoritative account" of the invention, which confirms 

 the Herald article to the minutest details. 



We fear Mr. Edison is thirty-five years behind the time 

 in his new invention. The patent-roll of Great Britain 

 for 1845 contains the specification of a lamp invented 

 by King, in which a thin rod of carbon was placed in an 

 exhausted globe ; and the inventor specially dwells on the 

 advantage of the Torricellian vacuum for the purpose. 

 A similar lamp was designed by Lodyguine in 1873. 

 The only difference between these lamps and that now 

 brought forward is that Edison prefers a different, and 

 apparently less durable, kindjoftprepared carbon to that 

 employed by his predecessors, though, again, in the 

 employment of carbonised paper he has been more than 

 once anticipated. 



We need not animadvert on the reckless and amusing 

 Vou xxi. — No. 537 



statements made by newspaper correspondents and inter- 

 viewers ; for these 4 accounts, we believe, Mr. Edison cannot 

 be held responsible. Mr. Edison's first steps in electric 

 lighting, we are told, were to invent a lamp and a generator. 

 The lamp consisted of a piece of platinum to be made in- 

 candescent, and so arranged that any excess of heat would 

 cause a small lever to cut off the current. It was an old 

 device described by Draper in 1847. The generator was, on 

 the other hand, a startling novelty. Instead of causing, as 

 in all ordinary dynamo-electric machines, a set of cils to 

 revolve about an axis in a magnetic field, Edison proposed 

 to mount the coils upon the prongs of a huge tuning-fork 

 which should be vibrated by a steam-engine. The friction 

 and waste of power inseparable from rotation wis to be 

 completely abolished. Unfortunately " the machine was 

 not practical, and it was laid aside." In ot 1 er words it 

 was a hopeless failure, wrong in design, wrong in prin- 

 ciple, useful only in showing how singularly devoid of 

 sound scientific knowledge a clever practical man may be. 

 The next iriea was to make the incandescent metallic 

 strip give light by proxy, causing it to communicate its 

 heat, either directly or by the intervention of reflectors, to 

 a piece of lime or zircon. The fusible nature of platinum, 

 however, spoiled his efforts, and he proposed expensive 

 alloys of iridium and osmium, only to find, what al 

 experimenters with incandescent metals had long known, 

 that there is a constant disintegration going on at the 

 surface and a consequent waste. Mr. Edison discovered 

 \ihat is for every student of the theory of electricity the 

 most simple and obvious conclusion from Joule's law, 

 namely, " that economy in the production of light from 

 incandescence demanded that the incandescent sub-tance 

 should offer a very great resistance to the passage of the 

 electric current." Forthwith the spirals of platinum, 

 iridium, and iridio-osmium were thrown aside. A carbon 

 filament prepared from charred paper, as described, was 

 adopted. It will be difficult to convince us that the 

 fragile horseshoe paper cinder will resist disintegration 

 better than the carbon used in exhausted tube^ by dozens 

 of other experimenters ; indeed the invention is avowedly 

 so recent that no lamp can have been tried for a period 

 of time long enough to warrant an assertion of its per- 

 manence. The latest telegrams from the States inform 

 us that Edison finds great difficulty in maintaining good 

 vacua, and that further experiments are necessary. It 

 must not be forgotten that even in a globe exhausted to 

 one-millionth of an atmosphere, there yet remain many 

 millions of millions of molecules of air enough to make 

 the disintegration of the incandescent carbon fibre only a 

 question of time. 



Meantime Edison had "discovered" — what had been 

 known in Europe for many months — that mercurial air- 

 pumps could be con tructed to exhaust to one-millionth 

 of an atmosphere; and, what is more to the point, he 

 found a workman formerly in the employ of the late 

 Hcrr Geissler, of Bom, to ma'-ce his pumps and ^'ass 

 bulbs for him. The tuning-fork generator had a. ready 

 been abandoned in favour of a new- generator, christened 

 the Faradc machine, which embodied no new principle 

 nor indeed any very important improvement in construe 

 tion, being essentially a modification of the well known 

 Siemens' machine, having a longitudinally-wound arma- 

 ture rotating between the poles of a powerful electro- 



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