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Feb. 27, 873 NATUREthe present pUl pose to inquire}, while all other sensations, as ofhearing, smell, before us only discontinuOltstyand from >Ill things nor alwaysthe same experience touch cannotbly co-operate regularly does in ours. Theof effective touch that gets associated withi s in the combining mobility andtiveness in ; and tne dog has no h,lllti.mobile limbs the extremities, and,has sensitive hasinf; no such active mobilityhuman hand limited in the scope of theirprehension. being defective, what is thetein the dog to play second sight, which as leader ne,:: s sUl?port,were it only because there tS not always lIght to see wIth? ::smell,I cannot but think, seeing that, while the organ is incontestablyacute. it has the great ad vantage over the tactile surface of thelips, of receiving impressions from things already at a distance.f we only suppose-what the facts make very likely-that thedog's smell is acute enough to have some scn",tion from allbodies without exception, nothing more is wanting to enable apsychologist to understand that the dog's world may be in themain a world of sights and sinells continuous in space. In thatcase a dog conveyed in a basket might by smell alone find its

back pretty much blindfolded finds his wayalone.To argue question is impossibleletter, and for reasons like thoserathe r than giving my adhesionWallace's as dogs are concerned.extent that source of explanation fornomen a which sufficiently constdered_explanation related even about dogsthan I would vrbc',her it is equally serviceableother .animals like cats and horses, concerninl{ which not lesswonderful stories are told, is not so clear_ Cats , however, seemto have very acute smell. 'What is the truth about the smell ofhorses? G_ CRUO"l R O D E R T S O ~University College, Feb. 24Fiords and l a ~ i a l Action

IN NATURE, vol. vii. pp. 94, 95, I find the. following; PoggeJZdorj's AnnalelZ-A. Helland adduces a large amountof evidence to show that the fiords in Norway have been formedby glad"l action."It appears and yet I have not metthat fiords t hose coasts wheregeographical must have been the mostaction. Tbe conditicn, for glacialevidently coast in a high andcold latitude, and snow-larlen westthe higher blow in (rom the ocean.conditions highest degree by theNorway lind : the western coastAmerica from IsLlnd northwards; and thecoast of South America. from Chil0e southwards; and thesecoasts ar e accordingly more cut up into fiords than any othersin the world.The western coa,t of America along the enormously long l i n ~from Vancouver's l s ~ n d to Chiloe is one of the most unbrokenin the world. It is significant that the change in the coast atChiloe from an unbroken one to one very much broken intofiords is accompanied by a great and compara ively abruptchange in the height of perpetual snow on the Andes_ Thefollowing are the heights of perpetual snow at three differentlatitudes, according to Mrs. Somerville's" Physical Gtogup'IY."The first two are north of Chiloe, the third south of it.12,7807.9603.390

Although snow-line deperids chieflytude, it is by the aspect of therespecting Learing wind,. The bestof this is Himalayas , where, accordingMrs. Somerville the height of the snowline16,620 feet and only 12 ,980 on theAccording to another a"thority (CapL S la,hey), qUGted hyMrs. Somerville (p. 54), the heights are 19,000 to 20,000 feeton the n01th and on the southern_ The differenceof the two the same_ The reason

difference is evidently that the south side receives the moisturewinds from the Indian Ocetm.Forge, DunIDurry MUll.PHY

ON A POLYDAC O O K H A M ~ j ) l c A Nkindness of Dr.have been able to procuremany curious pointson his peculiarities will interest saml;; of

NATURE.

~ R OMaidenhead, Icats; andthink a notethe readers of

Readers of Mr. Darwin's "Origin of Species JJ arefamiliar enough with the illustration he gives of correlation of arrest of development in the deafness of blueeyed cats. Some years ago I showed that our greatnaturali 't had fallen into error on this point, and that thecorrelation is not between the blue eyes and the deafness,but between the latter and the sex of the cat.I have made a great many inquiries on this point, andhave completely confirmed my (ormer observation, thatperfectly white tom-cats are they haveeyes occasionally, because beauty isamong white cats. many white

with blue eyes, but were deaf."Pudge" from Cookham deaf, andblue eye and a yellow first fewafter I had him, I thought little, butquite satisfied that complete,he is alive to soumis through solidA further point of intcre::t is he is not muteas most deafs are, but there is a kittenish shrillnessin his voice and a loudness in his purring, which are notcommensurate with his age_ I think, therefore, that itpossible that early in life he may have heard a little, for Iknow of two instances where perfect mutism accompaniedthe deafness in cats, and I do not know of any contrary

conditio l_ The olle yellow eye favours my view that" Pudge" may have heard in infancy his mother's voice.His sense of tOllch is extremely acute compared to that ofanother cat I have, but his sight ooes not seem so sharpof cats generally is. six digits,these are arranged-seven limb, andeach hind limb. The on thelimbs are thumbs, and are either si;e

tflle pollex, being joinedbones. In the hind limbof the same nature,

placed on the outer side 1tarsus by a completely-dtveloped

ON ACTION T A DISTANCEI HAVE no new discovery to bring before you thisevening. I Hlu't ask you to go over very oJd

ground, and to turn your attention to a question whichhas been raised again and again ever since men beganto think. .The question is that of the transmission of force. \Vesee that bodies at a distance from each other exert a

influence on each Does thi.,action depend on thc some thirdsome medium of occupying thebetween the bodies, or on eachimmediately v.:ithout the an) thing

mode in whichphcnomena of this kindother modem inquirers,tP enable you to place yourselves Farclddy"s pointof view, and to point out the scientific value of that con-

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Feb. 27, I873J N TUREbetweenof light.contact, Irings contract, several of

them vanish at the centre. Now it is possible to bringtwo pieces of glass 00 close together, that they will nottend to separate at all, but adhere together so firmlythat when torn asunder the glass will break, not at thesurface of contact, but at some other place. The glassesnow be many nearer than in mere

contact.e have shown bodies begin againsther while still measurable distance, and thateven when pressed together with great force they arc notin absolute contact, but may be brought nearer still, andthat by many degrees.Why, then, say the advocates of direct action, shouldwe continue to maintain a doctrine founded only on theexperience of age, matter can-where it is of admitting that all thefrom which Ollr ancestors concluded that contact isto action reali ty cases at a dis- Itance, the distance being too small to be measured by theirimperfect means of observation? I

f we are ever to discover the laws of nature, we mustdo so by obtaining the most accurate acquaintance withthe facts of nature, and not by cJressing up in phiJo-language the opinions of who had noof the wLich throw most on thesefor those introduce or othermedia, to account (or these actions, without any directevidence of the existence of such media, or any clearunderstanding of holV the media do their work, and whofill all space three and four times ov r with rethers ofdifferent sorts, why the less these men talk ahout theirscruples about admitting action at a

the better. were regulated Newton'sbe easy to opinionsin advance of the age. We should only have to comparethe science of to-day with that of fifty years ago, and byproducing, in the geometrical sense, the line of progress,we should obtain the science of fifty years hence.The progress of science in N ewton's t i m ~ consisted inrid of the machinery which gene-encumbered andthe sky."aJready got their crystalspheres, they were still swimming in the vortices ofDescartes. Magnets were surrounded by effluvia, and Ielectrified bodies by atmospheres, the properties of whichresembled in no respect those of ordinary effluvia andatmospheres.Newton dernonstraled that the which actsof the bodies depends relativewith respect other bodies, new theoryviolent from the advanced philo-sophers of the day, described the doctrine of gravi-tation as a return to the exploded method of explainingeverything by occult causes, attractive virtues, and thelike.Newton himself, with that wise moderation which ischaracteristic of all speculations, that hepretence of explaining the mechanism by whichheavenly bodies each otber. clrlermine thewhich their action on theirrelative position was a great step in science, and this stepNewton asserted that he had made. To explain the process by which this action is effected was a quite distinctstep, and this step, Newton, in his Principia, does notattempt to make .But so far was Newton from asserting that bodies reallydo act on one another at a distance, independently of any-

between them) which hasquoted by;, inconceivable s h ~ u l dthe mediation somethmg els.o) 5 not ma-terial, operate upon and affect other matter without mut ualcontact, as it must do if. g r a v i t a t i ~ l l , . in the sense of picurus, be essentIal and mherent m t That gravityshould be innate, inherent, and essential to matt er, so thatone hody can act upon another at a distance) through awithout mediation of else, by andwhich their and force conveyedto another, so great an that Ino man who . philosophicalpetent faculty of thmkmg can ever /all into it."Accordingly, we find in h:s Optical Queries," and in hisletters to Boyle, that Newton had very early. made the attempt to account for gravitation by means of the pressureof a medium, and that the reason he did not publish theseigations (rom hence that he foundnot able, and to giveaccount medium, manner ofoperation in the chief phcllomena of na-ture." *The doctrine of direct action at a distance cannot claimfor its author the discoverer of universal gravitation. twas first asserted by Roger Cotes, in his preface to the" Principia," which he edited during Newton' s life. Ac-to Cotes, it experience that that allgravitate. not learn in way thatextended, or solid. there-as much right considered pro-perty of matter as extension, mobility, or impenetrability.And when tbe Newtonian philosophy gained ground inEurope, it was the opinion of Cotes rather tban that ofNewtonthat became most prevalent, till at last Boscovichpropounded his theory, that matter is a congeri('s of ma-thern;llical points, each endowed with the of t t r a c ~ -

repelling the according te In hismatter is and contact impossible.not forget, to endow mathematicalpoints with inertia. In this some of the modern representatives of his school have thought that he had notquite got so far as the strict modern view of 'matter ' asbeing but an expression for modes or manifestations of'force.'' ' twe leave Ollt account for the the de-of the science, and our atten-the extension boundaries, see thatmost essential. Newton's should beextended to every branch of science to which it was applicable-that the forces with which bodies act on each othershould be investigated in the first place, before attemptingto explain tow that force is transmitted. Nomen couldbe better fitted to themselves exclusively to the firstthe problem, those who considered the secondunnecessary,Accordingly Cavendish, Coulomb, Poisson, theof the exact sciences of electricity and magne-tism, paid no regard to those old notions of magneticeffluvia" and electric atmospheres," which had been putforth in the previous century, but turned tbeir undividedattention to the determination of the law of force, according to which electrified and magnetised bodies attract oreach other. way the tme of thesewere discovered, this was men whodoubted that act.ion took distance,the intervc:ntion any medium, who wouldhave regarded the discovery of such a medium as complicating rather than as explaining the undoubted phenomena of attraction. (To e cOlltimled.

.;, 1\'brl011rin's Acco unt K w t O I l ' DiscoV'etics.t eview of ft.1rs, Somervilll' 's (, Molecular Science/' Saturday Revieu'}Feb. 13, 186g.

C)1873 Nature ublishing Group