130 



NATURE 



\_June 7, 1883 



3. With the constant element in the current — 



(a) With the positive pole against the apparatus. 



(b) With the positive pole against the disk in the 



earth. 



The deflexions obtained will give the particulars re- 

 quired for an easy calculation of the strength of the 

 current from the atmosphere to the earth. 



I am fully aware that several details of this method 

 may be open to discussion, but I do not deem others than 

 the following of any great importance, viz. that as the 

 intensity of the current is greatly dependent on the con- 

 dition of the points, a gradual oxidation of the same will 

 have the effect of causing an alteration in the current. 

 This alteration also takes place in the strength of the 

 current from the c instant element, so that even the de- 

 flexions caused by the same will always be a measure of 

 the aggregate potential due to induction, both through 

 the points and in the air. 



As it is not always possible to calculate the extent of 

 the deflexions, an instrument permitting part of the cur- 

 rent to be shunted should be employed. When the appa- 

 ratus is erected care should be taken that the height 

 between the disk in the earth and the apparatus is at 

 least 180 metres; but experiments with disks at various 

 elevations are of course of great interest. 



From the account I have thus given of my experiments 

 at Sodankyla, I think that all the subsidiary points which 

 should be taken into account, as well as those questions 

 which still await solution in connection with the aurora 

 borealis, will be readily comprehended. It would, how- 

 ever, be of great advantage when making similar experi- 

 ments to have two sets of apparatus; while thus measure- 

 ments are being made with one, the variations in the 

 current could be traced with the other, and thus the 

 particulars requisite for a reduction to a fixed mean 

 standard would be obtained. 



Selim Lemstrom 

 Professor of the Helsingfors University 



I 



HISTORICAL NOTES IN PHYSICS 

 I. — The Discovery of the Electric Light 



N looking through an old volume of the Journal de 

 Paris, I came across the following entry, for the 

 date 22 Ventose, An X. (March 12, 1802), which clearly 

 relates to an exhibition of the electric arc light : — 



" Le citoyen Robertson, auteur de la fantasmagorie, 

 fait dans ce moment, des experiences interessantes, et 

 qui doivent sans doute avancer nos connoissances sur le 

 galvanisms. II vient de monter des piles metalliques, au 

 nombre de 2500 plaques de zinc, et autant en cuivre 

 rosette. Nous parlerons incessament de ses re"sultats, 

 aussi que d'une experience nouvelle qu'il a faite hier avec 

 deux charbons ardens. Le premier e"tant place a la base 

 d'une colonne de 120 e'le'mens de zinc et argent, et le 

 second communiquant avec le sommet de la pile, ils ont 

 donnd, au moment de leur reunion, une e"tincelle brillante, 

 d'une extreme blancheur, qui a e"te apergue par toute la 

 socie'te'. Le citoyen Robertson re'pe'tera cette experience 

 le 25." 



The individual who thus came before the public was 

 named Etienne Gaspard Robertson, a name suggestive of 

 Scotch descent. He was better known for his " Phantas- 

 magoria," exhibited a few years later in London. 01 this 

 invention a notice appears earlier in the volume from 

 which the above passage is taken ; and in an earlier 

 volume of the Journal de Paris in the month " Fructidor, 

 An viii.," there occurs a mention of some of his experi- 

 ments on the couronne de lasses of Volta. 



It is worthy of casual notice that in the number where 

 Robertson's " Phantasmagoria" is advertised, the very next 

 advertisement on the page is one of an exhibition to be 

 given by Citoyen Martin at the Hotel de Fermes, where- 



in as part of a "spectacle extraordinaire et amusant de 

 physique,'' &c, was to be shown " I'expe'rience du te'le'- 

 graphie plus rapide que la lumiere, d'nn effet extraor- 

 dinaire et amusant." 



The usual date given for the invention of the electric 

 light by Sir Humphry Davy is 1809; but I was aware 

 that earlier notices existed both in Cuthbertson's " Elec- 

 tricity " (1807) and other works. I was also under the 

 impression that some earlier reference to the matter 

 existed in Davy's own works. The finding of this notice 

 in the Journal de Paris induced me to consult the early 

 volumes of the Philosophical Magazine and of Nichol- 

 son's Journal. 



In the Philosophical Magazine, vol. ix. p. 219, under 

 the date February 1, 1801, the following passage occurs 

 in a paper by H. Moyes of Edinburgh, in which experi- 

 ments with a voltaic pile or column are described : — 



" When the above column was at the height of its 

 strength its sparks were seen in the light of the day, even 

 when taken with a piece of charcoal held in the hand." 



In the Journal of tlie Royal Institution, vol. i. (1802), 

 Davy describes (p. 106) some experiments on the spark 

 yielded by the pile, and states: " When, instead of the 

 metals, pieces of well-burned charcoal were employed, 

 the spark was still larger and of a vivid whiteness." On 

 p. 214 he describes and depicts an "apparatus for taking 

 the galvano-electrical spark in fluids and aeriform sub- 

 stances." This apparatus consisted of a glass tube open 

 at the top and having a tubulure at the side through 

 which a wire tipped with charcoal was introduced, 

 another wire, also tipped with charcoal, being cemented 

 in a vertical position through the bottom. 



But earlier than any of these is a letter printed at 

 p. 150 of Nicholson' s Journal for October, 1800. This 

 letter is entitled " Additional Experiments in Galvanic 

 Electricity, in a Letter to Mr. Nicholson." It is dated 

 " Dowry Square, Hotwells, September 22, 1800," and is 

 signed by Humphry Davy, who at that time was assistant 

 to Dr. Beddoes at the old Philosophical Institution in 

 Bristol. The letter begins thus : — 



" Sir, — The earlier experimenters on animal electricity 

 noticed the power of well-burned charcoal to conduct the 

 common galvanic influence. I have found that this sub- 

 stance possesses the same properties as metallic bodies 

 in producing the shock and spark, 1 when made a medium 

 of communication between the ends of the galvanic pile 

 of Signor Volta." 



In none of these extracts, however, is anything said of 

 the properties of the arc as a continuous luminous spark. 

 These were made known in Davy's later researches. 

 Yet the electric light attracted attention as we see before 

 the special property of continuity was observed. 



II. — Tlie Invention of the Telephone 

 In the Journal of the Physical Society of Frankfort-on- 

 the-Main for 1860-61 (p. 57) may be found a memoir on 

 telephony by the galvanic current, in which its writer 

 says : " I have now succeeded in constructing an appara- 

 tus by means of which I am in a position to reproduce 

 the tones of divers instruments, and even to a certain 

 degree the human voice." The inventor further says : 

 " Since the length of the conducting wire may be extended 

 for this purpose just as far as in direct telegraphy, I give 

 to my instrument the name ' telephone.' " Towards the 

 end of the memoir it is stated that until now it had not 

 been possible to reproduce the tones of human speech 

 with a distinctness sufficient to satisfy everybody : "The 

 consonants are for the most part tolerably distinctly 

 reproduced, but the vowels not yet to an equal degree." 

 The author of the memoir in which these remarkable 

 statements occur was Philipp Reis. The paper from 

 which the preceding quotations have been taken contains 

 many other points of interest, and in particular a com- 



1 Here Davy adds a footnote ; ''The spark is most vivid when the char- 

 coal is hot." 



