NA TURh 



[January i6, 1908 



Carriire " raised several garden forms " of radish " of 

 various colours from the seed of the wild species (R. 

 rnphanistniin), and found that they produced the long 

 form in a light soil, and the turnip-rooted form in a stiff 

 soil. A similar result has occurred with carrots. By 

 selecting seed from plants having the best formed roots, 

 these " (characters) " have become fi.\ed and hereditary " 

 (" How to Study Wild Flowers," 1902). 



(2) I was delighted in the early summer by the marvel- 

 lous skill and intelligence exhibited by some collies in the 

 annual sheep-dog trials, which reveal apparently much 

 more than the results of individual training. I have lately 

 seen a pack of hounds streaming over the same country 

 after a fo.x. The hound (triste lupus in stabulis) would 

 make an indifferent sheep-dog, and the master who brought 

 a pack of collies to a meet would provide some novel sport 

 for the field. The collie is trained individually, but he 

 lias an inherent, if not ' inherited, aptitude, just as the 

 foolishly good-natured hound puppy who is " put out to 

 iiurse " in his earlier days readily learns his work when 

 he joins the pack. Further than this, an ordinary dog- 

 ^ho\v displays group peculiarities in different types of dog. 

 The fo.\-terriers snarl savagely at each other, the grey- 

 liounds and their allies bark and yelp continuously, and 

 appear as though on the verge of neurotic insanity, while 

 the foxhounds lie and appear to drowse silently with a 

 well-bred air of tolerant boredom that forms a curious 

 contrast to the howling multitudes around them. Yet 

 ihey are all dogs, and have reached their typical specialisa- 

 tion by characters acquired in some way. 



If we are forbidden to believe that acquired characters 

 are hereditary, what is the explanation of the seed of the 

 " student " parsnip and the " turnip " radish coming true 

 to type, and why does a collie drive sheep and a hound 

 give tongue at the scent of a fox? Is it suggested that 

 ill the " germ plasm " of the wild dog all these special 

 qualities are already involved, just as the digestive 

 peptones gathered functionally and localised in the leaves 

 of Dionasa and Drosera are found wandering aimlecsly 

 and to no purpose in some fruit trees? If so, what is the 

 nature of the directive impulse that localises these 

 characteristics in hound, collie, Drosera, and radish 

 immediately fertilisation takes place? And again, how 

 does the " peppered moth " contrive to appear in the 

 black country hatched with sooty wings that harmonise 

 with the now smoke-stained bark whereon he must rest? 

 The w-hole subject of mimicry seems to be involved, and 

 if your reviewer is right (N.ature, January 2, p. 193) in 

 noting with " a sense of weariness mingled with surprise 

 the appearance of a book on the transmission of acquired 

 characters, " it is quite certain that the "isolated bio- 

 logists, and whole hosts of medical men who still hold 

 the belief" that acquired characters are transmitted " would 

 regard it as a great boon if he would tell those who 

 " make him tired " what are the conclusions apparently 

 already established by " the modern, and still infant, 

 science of heredity " that will satisfactorily account for 

 such facts as I have ventured to state. 



It will hardly do to say that in one sense the problem 

 is " as unreal as the question of the apple dumpling which 

 puzzled one of the Georges, because the characters of an 

 organism do not get into its germ-cells any more than 

 the apple gets into its crust, for both the germ-cells and 

 ihc apple were there all the time." " One of the 

 < irorges " w^ould doubtless have been grateful for a little 

 eulinary instruction, just as " whole hosts " of somewhat 

 puzzled people with open minds would be honestly 

 sincerely grateful for a definite explanation from " the 

 infant science of heredity " as to how the sheep-driving 

 impulse really got into the sheep-dog. F"or " nature " is 

 more luminous than a text-book. E. C. Spicer. 



W'aterstock, Oxford, January 3. 



The Diamantiferous Rock of Kimberley. 

 Mv friend. Dr. H.atch, is not quite correct in stating 

 (January 9, p. 225) that I was led to dissent from the 

 late Prof. Carvill Lewis's view- that the diamantiferous 

 rock of Kimberley was a volcanic peridotite " by a micro- 

 scopic examination made in iSqq of specimens from the 

 Rowlands Mines " (Pror. Rov. Soc, Ixv., 1899, p. 223). 



NO. 1 994 VOL jy] 



Four years earlier 1 expressed the opinion that this rock was 

 a breccia, and that the diamonds, with other conspicuoui 

 minerals, were not formed in situ (Geol. Mag., 1895, 

 p. 500). This belief was strengthened rather than shaken 

 by editing Prof. Carvill Lewis's notes and examining his- 

 specimens (" The Genesis of the Diamond "), and was 

 expressed yet more decidedly later in 1897 after examining 

 another series of specimens from Kimberley (see Geol. 

 Mag., 1897, p. 501). To discuss the " magma " and 

 concretion " hypothesis would be out of place here, bur 

 elsewhere I may liave something to say on those subjects. 



T. d. BONXEV. 



Musical Sands. 



Mr. Cari's-Wilson's failure (January <i, p. 222) to 

 obtain sounds from " millet seed " sand of highh' spherical 

 grains puts a difficulty in the way of the suggestion made 

 in " Sound " by Poynting and Thomson, though I do not 

 think that it finally disposes of it. 



I have not been able to follow the friction explanation 

 as given by Mr. Carus-Wilson (Nature, August 6, 1891), 

 and I write in the hope that he may give more detail as 

 to the moving svsteni which produces the musical note. 

 It appears probable that the musical sounds excited in a 

 body by friction are due to the natural vibrations of that 

 body. Obviously the grains of sand are far too small 

 to give the notes heard. I suppose that the fundamental 

 period is of the order of the time taken by an elastic wave 

 to travel half round the grain. With elastic moduli of the 

 order 10'^ and densitv 25, the fundamental frequency would 

 be not less than 10". What system does the friction set 

 in vibration? J. H. Povnting. 



The University, Birmingham, January 11. 



In Nature of January 9 (p. 222) Mr. Carus-Wilson 's 

 letter asks for further details of the " singing sands " that 

 I exhibited to the Physical Society. I am able to give 

 the mineralogical description, by Mr. A. J. Maslen, of the 

 Maine sand from Mareen's beach, near Small Point, at 

 the entrance of the Kennebec River. 



A subangular sand very free from very small grains- 

 Clean. 



Quariz. Principal constituent. As perfectly colourless 

 grains showing conchoidal fracture (rock-crystal) and as 

 more or less coloured grains of quartzite. 



Muscovite Mica. Small quantity. Flakes. 



Glauconite. Dark green grains, many of fairly large 

 size. Almost black. 



Topaz (?) Square pieces due to cleavage. Yellow. 



Opaque white substance. (Felspar?) 



Magnetite. Small grains. Rare. 



The other specimens of sands w'ere very similar to tha^ 

 from Maine. Sidney Skinner. 



South-Wcstern Polytechnic, Chelsea, S.W., 

 January 13. 



Intensity of Spectrum Lines. 



Very little attention has been paid in the pa^t to the 

 accurate measurement of the optical intensity of spectral 

 lines in vacuum tubes under different conditions, probably 

 on account of the considerable experimental diHiculties. 

 Hence I may, perhaps, be allowed to indicate a relation 

 I have obtained between the optical intensity, current 

 strength, and pressure of the glowing gas. Throughout the 

 whole experimental range, using the so-called " electrode- 

 less " tube — with wholly external mercury electrodes, when 

 the current is of a slowly oscillating character — the optical 

 intensity. Yvith an end-on tube, is accurately proportional 

 to the readings of a thermo-galvanometer in series, and 

 over a more limited range of measurement, at constant 

 current, is inversely proportional to the pressure of the 

 t;as. 

 In other words, the intensity is proportional to A / ,-5/, 



where \ is the jnean free_ path. 



Measurements on the monatomic gases are now in 

 progress, and it is intended later to investigate the in- 

 fluence of temperature. A. D. CowPER. 



University College, London, W.C. 



