Sept. 30, 1875J 



NATURE 



475 



originality with which they are discussed, much valu- 

 able information on many intricate points which it 

 would be difficult if not impossible to find elsewhere. 

 The influence of Lake Ontario is seen in the diurnal 

 changes of the wind, which in July is nearly S. from 

 10 A.M. to 3 P.M., W. at 5 P.M., nearly N. at mid- 

 night, about which it remains till 9 A.M , when it 

 rapidly shifts to S.W., and ultimately to S. at 10 a.m. 

 From October to March, when storms are most frequent, 

 the greater depression of the barometer and increase of 

 vapour occur with winds from N.E. to S.S.E., and the 

 greatest rise of the barometer and diminution of vapour 

 with winds from W. to N.N.W. On the other hand, in 

 summer the greatest depression of the barometer occurs 

 with winds from E.N.E. to E.S.E., but the greatest in- 

 crease of vapour with winds from E.S.E. to S.S.W. Most 

 of the light falls of rain occur with winds from N.E. by 

 S. to \V., and of snow with winds from S.W. by N. to 

 N.E. ; most of the moderate falls of rain with winds from 

 N.E. to S_S.W., and of snow with winds from N.N.W. to 

 S.E. ; and most of the heavy falls of rain with winds from 

 N.E. to S.S.E., and of snow from N. to E.S.E. The im- 

 portant bearing of these facts on the question of North 

 American storms as well as on the climate of no incon- 

 siderable portion of that continent is evident. Tables II. 

 and XX. giving by interpolation-formute the mean tem- 

 peratures and mean pressures of different days of the 

 year, while of very slight scientific value, may be found 

 to be useful in a meteorological office, but a simpler and 

 in everyway more preferable table of normal daily values 

 for pressure and temperature could be constructed from 

 ihe arithmetic means of the thirty-one years' observations 

 treated by Bloxam's method of averages. 



LETTERS TO THE EDITOR 



\The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications. \ 



" Tone " and " Overtone " 



In the very favourable estimate of the work I have done in 

 my translation of Helmholtz, la your number for Sept. 23, I am 

 akcn rather severely to task for my use of '* Sensations of Tone" 

 on my title-page, and my refusal to use the expression overtones 

 in the body of the work. The title was long a matter of 

 anxious consideration to me, and I have not yet seen my way 

 to improving it. True, practical musicians, physiologists, and 

 artists have each their own, very different, technical meanings for 

 tone. The two last generally use it without an article, and in 

 the singular ; but musicians are accustomed to speak of " a tone," 

 or of several tones, when they allude to musical intervals. In 

 common speech, however, all three agree with the outside world 

 in speaking of a "loud and soft, gentle and angry tone of voice," 

 of a '* im^-toned instrument," of the " splendid or miserable tone 

 produced by a violinist," of the "magnificent tones of the 

 organ." That is, we are all accustomed to use tons, as I have 

 done on my title, for "a musical quality of sound." I know no 

 other single word in English which expresses the same concep- 

 tion. In the original German, Prof. Helmholtz (and af^er him 

 Prof. Tyndall) endeavours to use tone for a "simple tone " only. 

 Neither have contrived to be consistent in so doing. I have had 

 to correct the text several times in my translation on this very 

 point, and instead of using tone for " simple tone " only, which 

 is a new conception, and f/a«f (in English, a din) for "com- 

 pound musical tone," which is also a new and not an easy con- 

 ception, I have invariably used the word tone (except when 

 distinguished by a capital letter — thus. Tone, for the interval) in 

 tlie usual general sense of the word, and distinguished the par- 

 ticular cases by the prefix "simple" or "compound." It 

 seems to me that this is not so much "a little waywardness" on 

 my part, as a desire for scientific accuracy. 



As to " overtones," it is well known to those who, like my 

 reviewer, are acquainted with the work in the original, that 

 Helmholtz's expression ' ' Obertone " is a mere contraction for 

 " Ob°rtbeiltone " or " Oberparzialtone," both of which terms he 



not unfrequently uses, and these are literally rendered by my 

 "upper partial tones," Waiving my strong linguistic objection 

 to the term "overtones " as an English word, my scientific justifi- 

 cation for not using it in my translation must be sought for in the 

 fact that even the German " Obertone " has led Prof. Helmholtz 

 himself not unfrequently to its inaccurate use for "partial tones " 

 simply, including the lowest partial tone, which the word was 

 especially invented to exclude. Singularly enough, even my 

 reviewer has many times fallen into the same error (Nature, 

 p. 451, col. 2) in speaking of the "overtones" of a piano- 

 forte string. Thus he says, "the first six overtones are 

 all audible," which is not correct ; but he means " the lowest 

 partial tone and first /'z'^ of the upper partial tones," or briefly 

 "the first six partial tones," which is correct. Again, he says, 

 "the seventh and ninth (overtone) which are inharmonious, Sec, 

 which is not correct, for the seventh and ninth overionzs are the 

 eighth and tenth partial tones, and are perfectly harmonious; but 

 he meant the seventh and ninth partial tones. Again, he cites from 

 p. 126 of my translation, the relative force of the first six "partial 

 tones," as they are there called, but refers the table to the first 

 six "<7zv;-tones," which is altogether incorrect. Now if such men 

 as Helmholtz, who invented the term, and as my reviewer, who 

 uses it familiarly, can be led by it into what with them are mere 

 inaccuracies of expression, must we not look to the utmost con- 

 fusion of thought among persons to whom the whole subject is 

 new, and who employ the term with a very vague or loose con 

 ception of its meaning ? In point of fact, many such cases have 

 come to my notice. Hence, again, I cannot agree to think that 

 my deliberate rejection of the word "overtones" is " the chiel 

 fault" or "a blot on the translation," but rather submit that it is 

 a consistent endeavour to attain scientific accuracy of expression, 

 and avoid confusion of thought. 



I thank the reviewer for his generally favourable estimate, 

 gladly accepting his rectification ot the accidental Germanism 

 "the musically beautiful" for "the beautiful in music," and 

 I apologise for the length of this communication on the ground 

 that it is not a merely personal vindication, 



Sept. 25 Alexander J. Ellis 



^Colours of Heated Metals 



I HAVE just watched the casting in gun-metal, in an engineer- 

 ing establishment in this town, of what is intended to be the 

 rudder-post of a large vessel, which when completed will weigh 

 about three tons. As the casting was a simple one, it was 

 accomplished very quickly, and as the contents of the huge four- 

 ton ladle were emptied into the mould, the dazzling stream of the 

 metal flowed in a large volume over its lip. Brilliantly glossy it 

 appeared as it broke through the folds of thin dross with which 

 its surface was encrusted ; and this it did at the lip of the vessel, 

 while fold after fold of the encrusting pellicle was swept down 

 the stream, and left behind it a straight or ragged edge of the 

 thin film, from underneath which the metal welled out for a 

 moment with an appearance on the surface of perfectly trans- 

 parent purity. The appearance was a deception arising from the 

 strong bluish-green colour of the light emitted by the pure sur- 

 face of the metal, which I have never seen exhibited under 

 similar circumstances by melted iron or steel. It extended also 

 for only a short distance from the encrusting edge, the green 

 colour soon passing into white, or paler green, where exposure 

 to the air enveloped the metal again in a rapidly increasing 

 film of oxides that tarnish its surface and render the stream 

 white, or nearly so, in every part, excepting in a bluish-green 

 ring, or border where the fresh metal made its appearance, and 

 flowed over in a beautifully coloured stream from the mouth of 

 the ladle. The strongest patches of the colour there were tran- 

 sient, the film of oxide apparently soon thickening enough to 

 eclipse it, and by connecting itself to the broken edge of the thin 

 film in the pot to tear away another fold, when the characteristic 

 greenish glow of the metal immediately presented itself along 

 the freshly-broken edge. I had watched and thus interpreted 

 this beautifully varied play of natural colours in the molten 

 stream for some time before it occurred to me that the peculiar 

 hue of the freshly-exposed surface of the metal, glowing as it 

 does with the brightness of what in the black film of oxide 

 appears as white heat, is no other than the very colour of the 

 heated metal which the theory of exchanges would lead us to 

 expect. For as the colour of gun-metal in a cold state is yellow, 

 the selective absorption of its surface in that condition must 

 be exercised chiefly upon rays occupying the blue portion of 

 the spectrum, and consequently in the heated state these rays 



