294 



NATURE 



[Fed. I, 1877 



was long ago directed to its habits in this respect by Mr. Darwin 

 in his delightful " Naturalists' Voyage " (p. 33). He there men- 

 tions that when watching a male and female of this species in 

 flight, he "distinctly hear 1 a clicking noise, similar to that pro- 

 duced by a toothed wheel passing under a spring catch." 



This curious observation I had numerous opportunities of veri- 

 fying in the course of three visits to Rio Janeiro in 1866, 1867, 

 and 1869. Robert O. Cunningham 



Queen's College, Belfast, January 19 



I HAVE noticed that, when moles are burrowing, the worms 

 near make their way to the surface. I have also observed that 

 starlings gather round and under cows in pasture-fields. Their 

 doing so I have been in the habit of ascribing to the tread and 

 grazing-work of the cows producing tremors in the ground, 

 which worms may mistake for mole- work, and therefore crowd 

 to the surface ; and I have offered the same explanation for the 

 method of hunting pursued by blackbirds and thrushes. They 

 have practically found out that (earth-tremors induced by) small 

 hopping-runs make "the poor inhabitants below "seek safety 

 above, and that thus the hunters most readily secure a breakfast. 

 I am not acquainted with the habits of those hunters. 



Cambuslang Henry Muirhead 



Galton's Whistles 



Within the last few days I have had the opportunity of 

 making observations with Galton's wh'stle upon a large number 

 of people and upon some cats, and I have come to some conclu- 

 sions which are curious and suggestive, even though they may 

 not be absolutely exact. Thus, on the whistle a line is marked 

 which is the usual limit of human hearing, and which represents, 

 I should say, a number of vibrations somewhere between 41,000 

 and 42,000 per second. Out of many hundreds of persons exa- 

 mined I have only met with one instance, a young man, in which 

 I was satisfied that a note higher than this was heard. As a 

 rule the compass of the ear of women is markedly higher than 

 it is in men, and age seems to lower it sooner in men than in 

 women. Is this a result of the female animal always having the 

 more intimate protection of the young as her work, the young 

 having notes of higher pitch than the adult ? The fact is at 

 least suggestive. 



Very few of the persons experimented upon seemed to have 

 the compass of one ear exactly the same as that of the other, the 

 right ear usually hearing a higher note than the left, and this is 

 more marked in men than in women. 



The sense of direction of the sound in the human ear seems to 

 be lost at a very much lower point than appreciation of the note, 

 but this is not the case with cats ; for until the instrument ceases 

 to produce a note altogether, or at least one within their com- 

 pass, they turn their faces to the source of it the moment it is 

 produced. These facts are also suggestive. The cat still de- 

 pends to a large extent for its food supply on the appreciation of 

 high notes, and quite as much on the appreciation of the direc- 

 tion from which they come. The power of hearing a note of a 

 pitch beyond the limits of our sense of direction is suggestive 

 that that sense has been blunted by disuse ; and it would be 

 extremely interesting to know if the compass of direction is 

 higher in savage than in civilised peoples. From facts known 

 concerning their other senses, I should say it is likely to be 

 higher. 



This difference in the two compasses is further indicative that 

 the appreciation of direction is the work of a separate organ, 

 and IDr. Crum Brown's experiments suggest the semicircular 

 canals, or the utricle or succule in association with them, 

 as the seat of this sense. If, as Dr. Brown seems to have 

 shown, the semicircular canals are the organs of the general 

 sense of position and direction, it would not be a far- 

 fetched idea, that the utricle has to do with the sense of the 

 direction of sound and that the canals are additions to it. An 

 analogous relation of the cochlea to the saccule is suggested by 

 the mere facts of anatomy. If it be, as Helmholtz believes, that 

 the cochlea is the organ for the appreciation of J>itc/i, the rela- 

 tions of the three divisions of the organ of hearing are to be 

 easily understood, and these relations offer, at first sight, a singu- 

 larly strong evolutionary argument. There is, first, the organ 

 for the perception of sound vibrations, having a comparatively 

 limited compass. To this is added an organ for the appreciation 

 of the direction of the sounds, and another for the appreciation 



of highly-pitched notes ; and a part of the first of these becomes 

 so modified as to be capable of interpreting position and direc- 

 tion generally, independently of sound. The facts of the de- 

 velopment of the ear support such a view, and we may conclude 

 that the sense of direction is more important than the apprecia- 

 tion of high notes ; for the semi-circular canals appear, or at 

 least one exists, in the Myxine, whilst a very rudimentary cochlea 

 does not appear till we get high up in the fishes. 



Birmingham Lawson Tait 



Atmospheric Currents 



Mr. Clement Ley (in vol. xv. p. 157 of Nature) asks me 

 for the absolute proof which I suppose to exist (i) that the upper 

 current return trades "flowing from the equator descend again 

 to the surface of the ocean on the polar sides of the calms of 

 Cancer and of Capricorn," and (2) that " these equatorial currents 

 subsequent to their descent on the polar sides of Cancer and of 

 Capricorn are known as the westerly winds of the temperate 

 zones"; (3) he further asks "what proof exists that the upper 

 currents from the polar depressions and those from the equa- 

 torial depressions cross one another in the calms of Cancer and 

 of Capricorn so as subsequently to become the trades and anti- 

 trades respectively," and suggests that it is more reasonable to 

 suppose that their currents intermingle, and that their mixed 

 volume is then drawn off north and south, as required, to restore 

 the equilibrium of tlie atmosphere, as suggested by myself 

 with reference to the equatorial calms. Mr. Clement Ley's three 

 questions may, I think, be fairly answered as one, all depending 

 upon the same proof. 



The correctness of my assertions with reference to the atmo- 

 spheric currents flowing from the equator can be referred to the 

 one crucial test, viz. , Are the atmospheric currents which descend 

 to the surface of the ocean on the equatorial and on the polar 

 sides of the two zones of high pressure, similar in their consti- 

 tuents (i.e., when they first become established as winds on the 

 surface of the ocean) ? is their degree of electricity the same ? is 

 their degree of saturation the same? If these questions could be 

 answered in the affirmative it would show that Mr. Ley's suppo- 

 sition with reference to the mixed volume of the upper currents 

 was possible, but if, on the other hand, they are answered in the 

 negative, Mr. Ley can hardly hold, I think, that I have put my 

 statements forward too strongly. 



Though I believe that the north-east and south-east trades meet- 

 ing at the belt of equatorial calms are thrown upwards from thesur- 

 face of the ocean, and in ascending do mix their volumes, the 

 conditions of atmospheric currents meeting many thousand feet 

 above the sea-level are entirely different, as they have not the 

 ocean as a J>oiut (Tappui, and there is no more difliculty in 

 accounting for their currents passing one another and the heavier 

 underrunning the lighter, than there is tor the Labrador, aug- 

 mented by the East Greenland current, meeting and underrunning 

 the Gulf Stream. 



At Teneriffe, and other mountainous regions, in the latitudes 

 of the trades, observations have been made with reference to the 

 height of the trade winds, and of the neutral strata intervening 

 between them and the upper current, as also of the height of the 

 lower portion of the equatorial return current, which flows at 

 heights varying from 12,000 feet upwards above the sea-level. 



Prof. C. P. Smyth, H.M. Astronomer for Scotland, in his very 

 interesting work, " Teneriffe," gives us some very important data 

 with reference to these currents, showing — 



1. The extreme dryness of the north-east wind. 



2. Its very moderate electricity. 



3. The greater saturation of the south-west wind. 



4. The descent of the south-west upper current. 



5. The chemical difference between the two currents. 

 Though there is much that I might quote with advantage, I 



shall content myself with the following four paragraphs : — 



Page no. "If we must live in a wind by all means let it be 

 the south-west, and not the north-east, that effete unwholesome 

 and used-up polar stream. As to the chemical and sanitary 

 qualities of the two winds there could be no comparison between 

 them." 



Page 170. " And so indeed we found before we had finished 

 with our expedition, when the south-west wind descended to the 

 very surface of the sea." 



Page 184. "In short, whatever the north-east wind did, its 

 electricity was always moderate." 



Page 206. "The trade wind is undoubtedly a poor one for 



