February 24, 1910] 



NA TURE 



487 



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 intended for this or any other part 0/ Nature- 

 No notice is taken of anonymous communications.} 



The Meaning of " lonisation." 



I AM sorry that Prof. Walker (p. 458) has avoided my 

 question. .\t present I am not concerned either with his 

 position or with mine, with van der Waals or witli 

 Newton — I wisli simply to know what exactly he would 

 have us understand by the word ionisation. I hold that 

 it is our duty, as scientific workers, if possible, to be exact 

 in word as well as deed. It is a matter of reproach to us 

 that we should be lectured, year after year, from the 

 chair of the Royal Society, for our carelessness as writers. 

 Now that the attempt is being made to standardise all sorts 

 of things — from amperes and ohms to the members of iron 

 bridges, even by means of international congresses — we 

 might well devote some attention to our words and attempt 

 to standardise our scientific nomenclature. lonisation is 

 a word used with increasing frequency in these days — 

 unfortunately also with"^ increasing ambiguity. I would 

 appeal to Prof. Walker, as a leader among British physical- 

 chemists, at least to tell us what he wished us to under- 

 stand when using the word recently — as his meaning is in 

 no way made clear in his article. 



Henry E. Armstrong. 



The Flow of Sand. 



On Friday, February 11, I had the pleasure of hearing 

 Mr. C. E. S. Phillips deliver the discourse at the Royal 

 Institution, illustrated by many experiments, a number of 

 which showed that when sand escapes from an orifice at 

 the bottom of a long vertical tube it does not do so per- 

 fectly uniformly, but in a series of pulses which are 

 sufficiently rapid to produce audible sounds. Mr. Phillips 

 did not offer any suggestion as to the reason why the 

 flow is regularly intermittent, but two of his other experi- 

 ments, and the laws of friction, suggest a possible cause. 



One experiment showed sand forming a cone on being 

 poured from a funnel. The sloping sides of the cone gave 

 the angle of repose, and it was noticed that the sand at 

 first did not flow steadily down the slopes, but inter- 

 mittently. This, I think, may be due to a combination 

 of the momentum of the sliding sand and the difference 

 between the statical and dynamical friction between the 

 particles of the sand. A little heap of sand collects, then 

 the statical friction is overcome, and the momentum carries 

 the sand slightly too far, thus making the angle of repose 

 too small ; consequently the on-coming sand is able to 

 remain stationary on the slope until in turn its angle of 

 repose becomes too great, the statical friction is over- 

 come, and the cycle is repeated. The other experiment 

 showed how sand is self-supporting in a tube except for 

 the cone of sand at the base. Allow this cone of sand to 

 pass through the orifice, and the rest will fall intermittently 

 in the manner indicated. 



If this theory is correct, one would exnect sand with a 

 comparatively large coefficient of statical friction to give 

 fewer pulses per second than a sand having a smaller angle 

 of repose. A. S, E. Ackermann. 



25 Victoria Street, Westminster, London, S.W., 

 February 14. 



I AGREE with the explanation offered by Mr. Ackermann 

 in the first part of his letter, for it is evident that sand 

 must slip down itself by a series of rushes. 



The process, however, by which a mass of sand falling 

 in a glass tube produces musical sounds is somewhat more 

 complicated. The column must be regarded as consisting 

 of two parts, the upper portion acting simply as an inter- 

 mittently moving piston. It is the central region of the 

 lower part which becomes less dense, owing to escape of 

 sand through the orifice ; the upper portion, being no 

 longer supported, slips downward as a whole. 



The rapidity of its intermittent motion depends upon 

 the friction between the glass and sand. Hence the pitch 

 of the note is raised if the grains are better packed. The 

 action appears to resemble that of pushing a moist finger- 



NO. 2104, VOL. 82] 



tip along a polished table. The finger jumps rapidly and 

 regularly. 



As soon as the column so far lowers that the previously 

 compact upper portion begins to fall away at its centre, 

 all sound ceases. I showed at the Royal Institution 

 that by coating the inner surface of the glass tube 

 with oil, before filling it with sand, the column moved 

 downward by slow, regular jerks, increasing in rapidity 

 as the mass of the remaining sand in the tube grew less. 

 Here all friction between the glass and the sand grains 

 was eliminated, on account of the outer layer of particles 

 adhering to the oil and remaining as a coating upon the 

 tube. 



The jerks became more rapid as the inertia diminished 

 with the decreasing mass, which also explains why the 

 pitch of the note given out by a tube rises somewhat as 

 the sand column diminishes. 



Charles E. S. Phillips. 



Castle House, Shooters Hill, Kent, February 15. 



The Heredity of Sex. 



Current Mendelian theories of the heredity of sex are 

 based on the assumption that gametes are pure with respect 

 to sex characters ; that is, that a gamete may carry 

 the factor for maleness or the factor for femaleness, but 

 not both. This view may be expressed thus : — a gamete 

 carries M, the factor (or factors) for maleness, or F, the 

 factor (or factors) for femaleness, but not both M and F. 



The hypothesis proposed in this note suggests that the 

 phenomena of sex are due, not to a single pair of allelo- 

 morphic characters, but to two independent pairs of 

 characters, namely, maleness (M), with its allelomorph, 

 absence of maleness (m), which constitute one pair, and 

 femaleness (F), with its allelomorph (/), which constitute 

 the other ->air. On this hypothesis, since Mm, F/ are in- 

 dependent of one another, representatives of both pairs of 

 characters occur in every gamete. 



All gametes are therefore of one or other of the follow- 

 ing sex constitutions, MF, M/, mV, mf. Hence all zygotes 

 produced by the pairing of such gametes are of one or 

 other of the following nine gametic constitutions ; — 



1 MMFF-j 

 2MMF/I 



2 MwFF 9 ^'f 

 4M///F/J 



Dihybrid scheme- i M M^ \ -, m /■ 

 2 Mwf /3 ^/ 



1 /iimFF \ „ 



2 iiifiiFf p ""^ 

 immff I mf 



In zygotes MMFF and MmF/ it may be predicted that 

 circumstances, nutrition, &c., determine which type (male 

 or female) of sexual organs is produced. 



Thus double begonias, which bear female flowers, may 

 be induced by starvation to bear male flowers. Fern pro- 

 thalli, which bear normally male and female organs, 

 produce, when subjected to special treatment, male organs 

 only, and so on. 



In general, the numbers of " males " and " females " 

 among MMFF and MmF/, zygotes, will be about equal, 

 though wide departures from equality may occur in any 

 species owing to the prevalence of conditions which favour 

 the production of male or female organs. 



The following types of zygotes will, it may be supposed, 

 produce male sexual organs, MMF/, MMf, Mmff, and the 

 following, female organs, MmFF, mmFF, niniFf; hence 

 the number of males will equal the number of females 

 produced by such zygotes. 



The mmff, pure recessive type of zygote, if viable, is 

 sterile. The origin of sexuality connotes an origin of 

 sterility. To give examples of the application of the hypo- 

 thesis to biological facts : — 



A zygote of the MF type produces gametes of which all 

 or some carry MF. Species which have MF gametes will 

 be capable of exhibiting parthenogenesis (natural or 

 induced). Certain of the lower algee produce " gametes " 

 which may fuse in pairs to form zygotes, or may develop 

 directly into new individuals. Those which behave in the 

 former fashion may be such as carry M/ or mF, and 

 those which develop directly may be the MF gametes. 



