368 



NATURE 



[Fed. 14, 1889 



Natural History in the Field. 



Will you allow me to draw the attention of students of field 

 botany, field naturalists, and those interested in encouraging 

 natural history in the field, especially schoolmasters who may be 

 initiating classes for the study of our native plants, to the high 

 probability of the present year being quite an exceptionally 

 prolific year for ail our sun-loving vegetable flora. 



The want of sunshine last year kept all our wild flowers back. 

 Nothing had its full development : flowers were late, foliage was 

 thin, colours were dull and undefined, fruit small and without 

 flavour, seeds unripe. 



But one season's loss is the next season's gain ; in all prob- 

 ability the plants this year will be exceptionally fine, and many 

 plants that are usually small and poor will flourish with unusual 

 vigour, while, not improbably, many plants which seldom show 

 themselves here will this year blossom and become visible. 



On this account it might be well to advise the starting of 

 classes for the study this year of field natural history, for 

 students, particularly young students, are encouraged to go on 

 with a pursuit that has been very successful at its commencement. 



Chigwell. W. Linton Wilson. 



Detonating Meteor. 



According to the Jamaica Weather Report for November 

 1888, a very brilliant meteor was seen at Kingston, Jamaica, on 

 the evening of November 10, at 8h. 52m. local mean time. 



It appeared about 30° above the south-west horizon, crossed 

 the heavens, and disappeared about 30° above the north-north- 

 east horizon ; and as Kingston is in lat. 18° N., we have for the 

 point of appearance the celestial co-ordinates R.A. 2ih. 24m., 

 N. P.D. 1x3°, and for the point of disappearance, R.A. 3h. 

 4Sm., N.P.D. 2S°. 



Mr. R. Johnstone writes : — ' ' It was by far the brightest meteor 

 I have ever seen, and it so lit up the sky as to cause consterna- 

 tion among many of the negro population. Exactly four minutes 

 afterwards I heard a sound as of a distant explosion, which was 

 not quite so loud as the 9 o'clock gun at Port Royal, heard 

 in due time about four minutes later. The sound was heard by 

 other people in Kingston." 



As Kingston is 5h. 7m. W. of Greenwich, the meteor ap- 

 peared November 11, ih. 59m. a.m. Greenwich civil time ; and 

 therefore the meteor falls within the period November 11-15, 

 which is one of the lar?e-meteor periods, according to the 

 useful summary given in Whitaker's Almanac. 



The interval of four minutes between the appearance of the 

 meteor and the sound of its explosion corresponds to a distance 

 of forty-eight miles. I am sorry that the details are at present 

 incomplete in many re=;pects, but inquiry will be made. 



Maxwell Hall. 



12 Hartington Road, Ealing, February 2. 



MEMORIAL TO G. S. OHM. 

 A MEETING was held on Thursday afternoon, January 

 ■^"^ 31, in the meeting-room of the Royal Society, 

 the Right Hon. Lord Rayleigh, Sec.R.S., in the chair, 

 for the purpose of promoting the co-operation of English 

 men of science and others in a project, set afoot in the 

 first instance by some of the Professors and other leading 

 men in Munich, of erecting in that city a statue of George 

 Simon Ohm — a man who, although he discovered no new 

 phenomena of very striking importance, yet by the accu- 

 racy of his thought, and the clearness of his insight 

 into the true bearings of physical facts, was able to lay 

 one of the principal and firmest parts of the foundation 

 of the noble edifice of modern physics. 



The occasion for the proposal at this particular time to 

 erect a memorial to Ohm is the near approach of the 

 hundredth anniversary of his birth, on March 16, 

 1789. There are, moreover, reasons why this proposal 

 should be, and no doubt will be, taken up warmly in this 

 country. English physicists may recall with satisfaction 

 that the award of the Copley Medal by the Royal Society 

 on November 30, 1841, was the first public or official 

 recognition that Ohm received of the value of his work 

 upon the laws of the electric circuit, and that this award 



contributed in a very great degree to obtain for his 

 researches the attention and appreciation they deserved. 

 It may not be without interest at the present time to refer 

 to the words in which the Chairman, Sir J. W. Lubbock, 

 Bart, V.P. and Treas., announced the award. The 

 following is from the report of the proceedings at the 

 anniversary meeting of 1841 : — 



" The Council has awarded the Copley Medal for the 

 present year to Dr. G. S. Ohm, of Nuremberg, for his 

 researches into the laws of electric currents, contained 

 in various memoirs published in Schweigger' s Journal., 

 Poggendorff's Aniialen, and also in a separate work, 

 entitled ' i3ie galvanische Kette mathematisch bearbeitet,' 

 published at Berlin in the year 1827. In these works, 

 Dr. Ohm has established, for the first time, the laws of the 

 electric circuit ; a subject of vast importance, and hitherto 

 involved in the greatest uncertainty. He has shown that 

 the usual vague distinctions of intensity and quantity have 

 no foundation, and that all the explanations derived from 

 these considerations are utterly erroneous. He has 

 demonstrated, both theoretically and experimentally, that 

 the action of a circuit is equal to the sum of the electro- 

 motive forces divided by the sum of the resistances ; 

 and that whatever be the nature of the current, whether 

 voltaic or thermo-electric, if this quotient be equal, the 

 effect is the same. He has also shown the means of 

 determining with accuracy the values of the separate 

 resistances and electromotive forces in the circuit. The 

 light which these investigations have thrown on the theory 

 of current electricity is very considerable ; and although 

 the labours of Ohm were for more than ten years neglected 

 (Fechner being the only author who, within that time, 

 admitted and confirmed his views), within the last five 

 years, Gauss, Lenz,Jacobi, Poggendorff", Henry, and many 

 other eminent philosophers, have acknowledged the great 

 value of his researches, and their obligations to him in 

 conducting their own investigations. Had the works of 

 Ohm been earlier known, and their value recognized, the 

 industry of experimentalists would have been better 

 rewarded. In this country those who have had most 

 experience in researches in which voltaic agency is con- 

 cerned, have borne the strongest testimony to the assist- 

 ance they have derived from this source, and to the 

 invariable accuracy with which the observed phenomena 

 have corresponded with the theory of Ohm. This 

 accordance it may be observed is altogether independent 

 of the particular hypothesis which may be adopted as to 

 the origin of electromotive force ; and obtains equally, 

 whether that force is regarded as being derived from the 

 contact of dissimilar metals, or as referable to chemical 

 agency." 



Ohm's book, "Die galvanische Kette," referred to in the 

 above extract, was translated into English by Dr. William 

 Francis, and published in 1841, in the second volume 

 of "Taylor's Scientific Memoirs." The pubhcation of 

 Wheatstone's paper (read to the Royal Society, June 15, 

 1843), entitled "An Account of several New Instruments 

 and Processes for determining the Constants of a Voltaic 

 Circuit," also contributed in an important degree to at- 

 tract attention to Ohm's work and to cause its importance 

 to be recognized. We may call to mind also that it was 

 in this country that the necessity of expressing electrical 

 quantities in absolute measure first came to be generally 

 recognized, and that the term " ohmad " or " ohm," sug- 

 gested by Sir Charles Bright and Mr. Latimer Clark at 

 the meeting of the British Association in Manchester, in 

 1 86 1, first came into use as the name of a decimal 

 multiple of the absolute unit of resistance convenient for 

 practical purposes. Twenty years later, at the Congress 

 of Electricians in Paris, in 1881, the "ohm" was unani- 

 mously adopted as an international standard. The name 

 of the modest German Professor has thus come to be 

 an understood term in the language of every civilized 

 community in connection with the conception which he 



