374 



NATURE 



[March 23, 1922 



Dr. E. J. Salisbury in a paper published in conjunction 

 with the Phenological Report for 1920 (Q. J.R. Meteor. 

 Soc, October 1921). 



The average dates of leafing, flowering, etc., of a 

 particular species is the result of prolonged adaptation 

 to climate, and whilst the deviations of particular 

 individuals from that date is controlled in part by local 

 conditions of habitat, etc., the deviations of the same 

 individuals in different years are governed not only 

 by the weather of the current season but also by 

 that of the previous season. The deviations from 

 year to year are really kept within remarkably 

 narrow limits, and there can be no doubt that force 

 of habit is all - important in causing the periodic 

 processes of vegetation to occur as near to the same 

 dates year by year as external meteorological vicissi- 

 tudes will permit. L. C. W. Bonacina. 



27 Tanza Road, Hampstead, N.W.3, March 12. 



The Resonance Theory of Hearing. 



Dr. Perrett will, I hope, excuse me if I have 

 seemed to impute absurdities to him (Nature, 

 February g, p. 176). My reason for replying to his 

 letter was because it seemed 

 to me unfair to the reson- 

 ance theory to leave his 

 criticism unquestioned. 

 But perhaps the considera- 

 tion of an example will help 

 to bridge the difference of 

 opinion between us. Prof. 

 Millar in his " Science of 

 Musical Sounds " has given, 

 on p. 201, analyses of the 

 intensities of the harmonics 

 of the oboe and clarionet. 

 Whereas the clarionet note 

 has harmonics of which the 

 8th, 9th, and loth are the 

 strongest, in the oboe note, 

 on the other hand, the 4th 

 and 5th harmonics have the 

 greatest intensity If, then, 

 the ear heard both these 

 instruments sounding the 

 same tone at one and the 

 same time, it would hear 



one fundamental accompanied by strong 4th, 5th, 

 8th, gth, and loth harmonics. 



Now no musical instrument of which Prof. Millar 

 gives the analysis has these harmonics strongly 

 marked, and the chances are enormously against 

 any one musical instrument whatever having pre- 

 cisely the same intensities of the harmonics as those 

 of the oboe and clarionet sounding the same tone 

 together. In other words, there is something quite 

 unique about the harmonics in the case that I have 

 taken, which should enable the observer to say that 

 the sound is to him not like an oboe only, or a clarionet 

 only, but as if an oboe and a clarionet were speaking 

 the same tone at the same moment. Now I do not 

 say that the ear can never be deceived, for Helmholtz 

 himself showed that vowels even, can be imitated by 

 means of tuning-forks, but it seems to me that 

 the characteristic intensities of harmonics do in 

 almost all cases enable an observer to recognise the 

 sounds of different classes of musical instruments 

 even when any two of them are playing the same 

 tone. Let us turn finally to the case which Dr. 

 Perrett mentions, namely, when the voice is accom- 

 panied by the same tone produced by the chattering 

 teeth. We know from the works of Helmholtz, 

 Millar, and many others that the voice overtones 

 have one maximum of intensity for the vowels " o " 

 and " a " and two maxima for " e," " i " and " u," 



NO. 2734, VOL. 109] 



other overtones being very weakly represented. We 

 also know that discontinuous sounds, such as those 

 produced by tooth striking tooth, are very rich in 

 overtones, and that these do not occur in maxima 

 in any definite way. We should, therefore, expect 

 the voice and the teeth-sound to have overtones very 

 different in their intensity distribution. Therefore 

 the observer should, so far as one can judge, hear 

 overtones as characteristic on which to base his 

 judgment, as those given out by oboe and clarionet. 



I must, therefore, repeat that, in my opinion. Dr. 

 Perrett is mistaken in his objection to the resonance 

 theory. H. Hartridge. 



King's Coll., Cambridge. 



Snow Furrows and Ripples. 



While at Gstaad recently, after a fine fall of snow 

 (about 24 inches), the F5hn blew and rain fell for 

 some hours. The weather then cleared, the tempera- 

 ture falling below freezing-point, and the snow then 

 presented the appearance shown on the accompany- 

 ing picture (Fig. i). The peculiar " sillone " appear- 

 ance of the snow on the slopes is very striking. It 



looks as though water had run down over the surface, 

 but this did not happen during the rain or afterwards. 

 As to the origin of the " furrows " (sillons), I 

 think they were caused by contraction of the snow, as 

 the gentle rain wet the fine-grained snow particles 

 and drew them together. I observed afterwards the 

 same development of furrows during fine weather 

 on sunny slopes. These were so shallow that I 

 failed to photograph them, but the whole hillside 

 was covered with them. I also noticed that they 

 occurred on the low-lying flat meadows, although 

 they had no particular orientation in that case and 

 occurred in every direction. This may be discerned 

 in the lower parts of Fig. i. E. C. Barton. 



I WAS once out on the snow-covered prairie at 

 Moose Jaw, Saskatchewan, when suddenly, the 

 hot Chinook wind began to blow, the counterpart of 

 the Alpine fohn. The snow melted away with 

 astonishing rapidity, and very soon there was the 

 sound of trickling water, which I had not heard for 

 months, for the season was late winter. The melting 

 was not uniform, nor did it produce longitudinal 

 furrows, but on the contrary a rippled structure of 

 ridges and furrows transverse to the wind, adding 

 yet one more variety to the many kinds of ripples 

 which I had seen in snows of different consistency. 

 Vaughan Cornish. 



