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can never be transformed into a mammal.” There is something great delusion if anyone were to believe that he had arrived at more therefore than blind chance at work here.
a comprehension of the universe by tracing the phenomena of But within the limits, it is a matter of experience that every Nature to mechanical principles" (p. 710). possible variation may occur. If anyone will take the trouble In truth, this revolt of teleology against Darwinism is a little to examine the leaves of the ribbon-grass so commonly cultivated ungrateful. For, if Darwinism has done anything, it has carried in gardens, he will find it impossible to obtain any pair in which on and indefinitely extended its work. In the last century, the green and white striping is exactly alike. If it were pos- teleology was, it seems to me, a valuable motive power in takes sible to raise to maturity all the progeny of some prolific organ logical research. Such a book as Derham's **Physico-Theology" ism, the same diversity in different degree, of course) would (1711) may be read with interest even now. I well remember manifest itself; but the whole group of variations in respect of that my first ideas of adaptive structures were obtained from the any one organ would obey Quetelet's law. When we attempt pages of Paley. Thirty years ago I do not know, except fram to give some physical explanation of this fact, we know from them and the notes to Darwin's * Botanic Garden," where such the objective facts which have been made out about fertilization information was to be otained. The basis of research was, that, although the protoplasmic content of the fertilized ovum however, too narrow to continue ; it did not look beyond the is, in a general sense, uniform, its actual structure and physio- welfare of the individual. The more subtle and recondite spring logical components must be combined in as endless variety as of adaptation opened up by the researches of Darwin, which look the green and white stripes of the leaves of the ribbon-grass to the welfare of the race, were not within its purview. Conse: If, with Prof. Lankester, we say that the combinations are quently it dried up, and virtually expired with the Bridgewates kaleidoscopic, I do not see that we go beyond the facts. And Treatises. it appears to me quite permissible to correlate the ascertained To return, however, to the Duke of Argyll. " Neither variable constitution of the ovum arising from this cause with mechanical aggregation, nor mechanical segregation, can possibly the equally ascertained varying structure of the organism deve-account for the building up of organic tissues." Who has said loped from it.
they did ? The Duke has entirely misunderstood the matte Of the varied progeny, we know that some survive and others. Prof. Lankester never suggested that it was possible to put on do not. And what Darwin has taught us is, that the reason of much protoplasm into a vessel, and shake out a cockatou or survival is the possession of favourable variations. The surviving guinea pig at choice. His image of the kaleidoscope has race necessarily differs somewhat from its progenitors, and Dar, nothing to do with the building up of organisms, only with th win has further stated that it is probable that by the continued varied combination of the elements known to take part in de repetition of the process all the diversity of organic nature has formation of the fertilized ova from which organisms originate. been brought about.
| I am not sure that I perfectly comprehend what follows The area of fortuity is narrowed down therefore, on this point Perhaps some further emendation than that already published i of view, to the variable constitution of the individual ovum. needed in one of the sentences. But it seems evident that the And it is upon the recognition of this fact, for which there seems Duke is re-stating his old doctrine of "prophetic germs." He to be good scientific evidence, that the Duke of Argyll founds his has already defined what he means by these (NATURE, 1o! charge that the neo-Darwinians make fortuity their idol. The xxxviii. p. 564). “All organs," he says, " do actually psan reason appears to be that it comes into collision with teleological through rudimentary stages in which actual use is impossible." views. But such collisions are no new event in the history of Here, again, as in the case of the transmission of acque the biological sciences. And teleology, like a wise damsel, has characters, what one wants is not a reiteration of the assertion generally, though temporarily ruffled, managed to gather up her ' but some definite observed evidence. For the production skirts with dignity and make the best of it. For some element this, if only in a single instance, Prof. Lankester pressed the of fortuity is inseparable from life as we see it. It is at the Duke more than a year ago (NATURE, hr. p. 58%). None, bottom one of the most pathetic things about it. Nowhere is | however, has as yet been forthcoming; and it appears to the this more vividly portrayed perhaps than by Addison in the, that it is not permissible to persist in statements for which be * Vision of Mirzah." Yet I do not remember that anyone was does not attempt to offer a shadow of proof. ever so unwise as to taunt Addison with making fortuity his idol. The Duke exults in a very amazing fashion over what ne
But, philosophically considered, what is gained by this tenacity strangely calls Prof. Lankester's admission that "natural sele about out-works? 1 reply, exactly as much as was gained by tion cannot account for the pre-existence of the structures which the tenacity of the Church in respect to the geocentric theory of are prescribed for its choice." I am afraid I have already tre the planetary system. Scientific men cannot be stopped in the passed on your space too much with quotations ; but i hava application of their best ability to the investigation of Nature. If done so in order to show, in some measure at any rate, what their conclusions are false, they will detect the falsity; if true, the consensus of opinions amongst students of Darwinism; they will not be deterred from accepting them by some a priori I must answer the Duke with one more from Prof. Huxler. conception of the order of the universe. It is not justifiable to admirable biography. It is true that the Royal Society publisere say that this is due to any devotion to such an empty abstraction these things in the least attractive way possible ; but this per as fortuity. No scientific man is, I hope, so foolish as to suppose ticular paper could hardly have escaped attention, as it won the that, however completely mechanical may be his conception of notice and admiration of even a journal so little occupied wish Nature, he is in any way competent to account for its existence. scientific discussion as Truth. The real problem of all is only pushed further back. And the " There is another sense, however, in which it is equally tre Duke of Argyil's difficulty resolves itself into the old question, that selection originates nothing. Unless profitable variations whether it is more orthodox to conceive of the universe as an .:: occur, natural selection can do nothing' ("Origin,' ed. I. automatically self-regulating machine, or as one which requires p. 82! Nothing can be effected unless favourable variation tinkering at every moment of its action.
occur' (1.6., p. 108). "What applies to one animal will apply It may be replied that this is all very well, but that it is not throughout time to all animals-that is, if they vary—for others the way the neo-Darwinians state their case. I may be, there- natural selection can do nothing. So it will be with plants.l.. fore, excused for quoting some passages to the contrary from p. 113: Strictly speaking, therefore, the origin of specia Weismann's “Studies in the Theory of Descent":
general lies in variation; while the origin of any particule * This conception represents very precisely the well-known species lies, firstly, in the occurrence, and, secondly, in the decision of Kant: 'Since we cannot in any case know a priori selection and preservation of a particular variation. Cleanes to what extent the mechanism of Nature serves as a means to , on this head will relieve one from the necessity of attending to every final purpose in the latter, or how far the mechanical ex- the fallacious assertion that natural selection is a deu a mariik, planation possible to us reaches, natural science must every or occult agency." where press the attempt at mechanical explanation as far as And the Duke says he has been waiting for this for thirty possible” (p. 638).
years. One can only wonder what Darwinian literature bas Further, he quotes from Karl Ernst von Baer :
been the subject of his studies during that time, * The naturalist must always commence with details, and may
W. T. THISELTON DIEL. then afterwards ask whether the totality of details leads him to Royal Gardens, Kew, January 6. a general and final basis of intentional design " (p. 639). Again, he says: "We now believe that organic nature must be conceived as
The Microseismic Vibration of the Earth's Crust. mechanical. But does it thereby follow that we must totally
In Mr. White's article on British earthquakes (NATCRE, Jan. deny a final universal cause ? Certainly not; it would be a P. 202) he refers to me as having discevered the microseismic
vibration of the earth's crust. My brother Horace and I were, of those salient properties of magnetism as exhibited by we believe, the first to verify in England the observations of iron, nickel, and cobalt-properties most of them very Bertelli, Rossi, d'Abbadie, and the other (principally Italian) familiar, but properties which any theory of magnetism pioneers in this interesting subject.
must reckon with and explain. We shall not touch on In our Reports to the British Association for 1881 and 1882 the great subject of the earth as a magnet-though much me "The Lunar Disturbance of Gravity," some account will be has been recently done, particularly by Rücker and trund of the earlier literature on the subject. January 9.
G. H. DARWIN.
Thorpe--but deal simply with magnetism as a property
of these three bodies, and consider its natural history, Meteor.
and how it varies with the varying condition of the
material. üx Sunday, 12th inst., about 8.10 p.m., a bright meteor To fix our ideas, let us consider, then, a ring of uniform was so here, coming into view near :* Aurigæ. It was of a section of any convenient area and diameter. Let us supreddish colour, moved slowly, leaving a short tail, and burst pose this ring to be wound with copper wire, the convolusteve . Leonis
, then with diminished light continued its course tions being insulated. Over the copper wire let us suppose to the horizon.
T. W. MORTON. Beaumont College, Old Windsor, January 13.
that a second wire is wound, also insulated, the coils of each wire being arranged as are the coils of any ordinary modern transformer. Let us suppose that the ends of the
inner coil, which we will call the secondary coil, are conMAGNETISM.
nected to a ballistic galvanometer ; and that the ends of I.
the outer coil, called the primary, are connected, through Sold as any part of electrical science is the knowledge a key for reversing the current, with a battery. If the
that a needle or bar of steel which has been touched current in the primary coil is reversed, the galvanometer with a loadstone will point to the north, Long before the needle is observed to receive a sudden or impulsive deflecfirst experiments of Galvani and Volta the general pro- tion, indicating that for a short time an electromotive perties of steel magnets had been observed --how like force has been acting on the secondary coil. If the repoles repelled each other, and unlike attracted each other; sistance of the secondary circuit is varied, the sudden how the parts of a broken magnet were each complete deflection of the galvanometer needle varies inversely as magnets with a pair of poles. The general character of the resistance. With constant resistance of the secondary the earth's magnetism has long been known that the circuit the deflection varies as the number of convolution's earth behaves with regard to magnets as though it had in the secondary circuit. If the ring upon which the two magnetic poles respectively near the rotative poles, coils of copper wire are wound is made of wood or glass ind that these poles have a slow secular motion. For | –or, indeed, of 99 out of every 100 substances which many years the earth's magnetism has been the subject could be proposed —we should find that for a given of careful study by the most powerful minds. Gauss current in the primary coil the deflection of the galvanoorganized a staff of voluntary observers, and applied his meter in the secondary circuit is substantially the same. yasturpassed powers of mathematical analysis to obtaining The ring may be of copper, of gold, of wood, or glassfrom their results all that could be learned.
it may be solid or it may be hollow-it makes no difference The magnetism of iron ships is of so much importance in the deflection of the galvanometer. We find, further, ta navigation that a good deal of the time of men of that with the vast majority of substances the deflection of great power has been devoted to its study. It was the the galvanometer in the secondary circuit is proportional Hientific study of Archibald Smith ; and Airy and to the current in the primary circuit
. If, however, the Thomson have added not a little to our practical know- ring be of soft iron, we find that the conditions are enorledge of the disturbance of the compass by the iron of mously different. In the first place, the deflections of the the ship. Sir W. Thomson, in addition to much valuable galvanometer are very many times as great as if the ring practical work on the compass, and experimental work on were made of glass, or copper, or wood. In the second magnetism, has given the most complete and elegant place, the deflections on the galvanometer in the secondary mathematical theory of the subject of late years the circuit are not proportional to the current in the primary development of the dynamo machine has directed circuit; but as the current in the primary circuit is step a'tention to the magnetization of iron from a different by step increased we find that the galvanometer deflecpunt of view, and a very great deal has been done by tions increase somewhat, as is illustrated in the acsany workers to ascertain the facts regarding the companying curve (Fig. 1), in which the abscissæ are magnetic properties of iron. The upshot of these many proportional to the primary current, and the ordinates are years of study by practical men interested in the mariner's proportional to the galvanometer deflections. You obcompass or in dynamo machines by theoretical men
serve that as the primary current is increased the galvanointerested in looking into the nature of things, is, meter deflection increases at first at a certain rate ; as that although we know a great many facts about mag- the primary current attains a certain value the rate at hetists, and a great deal about the relation of these facts which the deflection increases therewith is rapidly into each other, we are as ignorant as ever we were as creased, as shown in the upward turn of the curve. This o any reason why the earth is a magnet, as to why its rate of increase is maintained for a time, but only for a magnetic poles are in slow motion in relation to its sub- time. When the primary current attains a certain value stance, or as to why iron, nickel, and cobalt are magnetic, the curve bends downward, indicating that the deflections ind nothing else, so far as we know, is to any practical of the galvanometer are now increasing less rapidly as Falent. In most branches of science the more facts we the primary current is increased ; if the primary current know the more fully we recognize a continuity in virtue of be still continually increased, the galvanometer deflections which we see the same property running through all the increase less and less rapidly. rarious forms of matter. It is not so in magnetism ; here
Now what I want to particularly impress upon you is he mare we know the more remarkably exceptional does the enormous difference which exists between soft iron on be property appear, the less chance does there seem
to the one hand, and ordinary substances on the other. On of resolving it into anything else. It seems to me that this diagram I have taken the galvanometer deflections I cannot better occupy the present occasion than by re- to the same scale for iron, and for such substances as alling your attention to, and inviting discussion of, some glass or wood. You see that the deflections in the case
of glass or wood, to the same scale, are so small as to be neis de Tharaday, January 9, by J. Hopkinson, M. A., D.Sc., F.R.S., one point of the curve is something like 2000 times as " laauparal Address delivered before the Institution of Electrical En: absolutely inappreciable, whilst the deflection for iron at Toadette
great as for non-magnetic substances. This extraordinary galvanometer, are called induction, and that the abscisse property is possessed by only two other substances are called magnetizing force. Let us see a little more besides iron-cobalt and nickel. On the same figure are precisely what we mean by the terms, and what are the curves showing on the same scale what would be the units of measurement taken. The elongation of the deflections for cobalt and nickel, taken from Prof. galvanometer measures an impulsive electromotive force Rowlands’s paper. You observe that they show the same an electromotive force acting for a very short time. general characteristics as iron, but in a rather less degree. Charge a condenser to a known potential, and discharge Still, it is obvious that these substances may be broadly it through the galvanometer : the needle of the galvanoclassed with iron in contradistinction to the great mass of meter will swing aside through a number of divisions other bodies. On the other hand, diamagnetic bodies proportional to the quantity of electricity in the condenser belong distinctly to the other class. If the deflection with —that is, to the capacity and the potential. From this a non-magnetic ring be unity, that with iron, as already we may calculate the quantity of electricity required to stated, may be as much as 2000; that with bismuth, the give a unit elongation. Multiply this by the actual remost powerful diamagnetic known, is o‘999825—a quantity sistance of the secondary circuit and we have the impulsive differing very little from unity. Note, then, the first fact electromotive force in volts and seconds, which will, in which any theory of magnetism has to explain is : Iron, the particular secondary circuit, give a unit elongation. nickel, and cobalt, all enormously magnetic ; other sub- | We must multiply this by 108 to have it in absolute C.G.S. stances practically non-magnetic. A second fact is: units. Now the induction is the impulsive electromotive With most bodies the action of the primary current on force in absolute C.G.S. units divided by the number of the secondary circuit is strictly proportional to the secondary coils and by the area of section of the ring in primary current; with magnetic bodies it is by no square centimetres. The line integral of magnetiang means so.
force is the current in the primary in absolute C.G.S. units You will observe that the ordinates in these curves, —that is, one-tenth of the current in amperes-multiplied which are proportional to the kicks or elongations of thé by 4t. The magnetizing force is the line integral divided
by the length of the line over which that line integral is be the substance of which the ring is composed, the distributed. This is, in truth, not exactly the same for galvanometer deflection is one-half of what it would have all points of the section of the ring-an imperfection so been if the primary current had been reversed. I shoulu far as it goes in the ring method of experiment. The perhaps say approximately one-half, as it is not quite absolute electro-magnetic C.G.S. units have been so strictly the case in some samples of steel, although, chosen that if the ring be perfectly non-magnetic the broadly speaking, it is one-half. This is natural enough induction is equal to the magnetizing force. We may for the exciting cause is reduced from—let us call it a refer later to the permeability, as Sir W. Thomson calls positive value, to nothing when the secondary coil is it; it is the ratio of the induction to the magnetizing withdrawn; it is changed from a positive value to an force causing it, and is usually denoted by M.
equal and opposite negative value when the primary There is a further difference between the limited class current is reversed. Now comes the third characteristic of magnetic bodies and the great class which are non- difference between the magnetic bodies and the nonmagnetic. To show this, we may suppose our experiment magnetic. Suppose that, instead of plucking the ring with the ring to be varied in one or other of two or three apart when the current had a certain value, the current different ways. To fix our ideas, let us suppose that the was raised to this value and then gradually diminished to secondary coil is collected in one part of the ring, which, nothing, and that then the ring was plucked apart and provided that the number of turns in the secondary is the secondary coil withdrawn. If the ring be mosmaintained the same, will make no difference in the magnetic, we find that there is no deflection of the result in the galvanometer. Let us suppose, further, galvanometer ; but, on the other hand, if the ring be that the ring is divided so that its parts may be plucked of iron, we find a very large deflection, amounting, it may from together, and the secondary coil entirely withdrawn be, to so or 90 per cent of the deflection caused by the from the ring. If now the primary current have a withdrawal of the coil when the current had its full value certain value, and if the ring be plucked apart and the Whatever be the property that the passing of the primary secondary coil withdrawn, we shall find that, whatever current has imparted to the iron, it is clear that the iron
retains a large part of this property after the current has upon them by the primary current has been called by ceased. We may push the experiment a stage further. Prof. Ewing “hysteresis," or, as similar properties have Suppose that the current in the primary is raised to a been observed in quite other connections,“ magnetic great value, and is then slowly diminished to a smaller hysteresis." The name is a good one, and has been value, and that the ring is opened and the secondary adopted. Broadly speaking, the induction as measured coil withdrawn. With most substances we find that by the galvanometer deflection is independent of the time the galvanometer deflection is precisely the same as if during which the successive currents have acted, and the current had been simply raised to its final value. It depends only upon their magnitude and order of succesis not so with iron : the galvanometer deflection depends sion. Some recent experiments of Prof. Ewing, however, not alone upon the current at the moment of withdrawal, seem to show a well-marked time effect. There are but on the current to which thering has been previously sub- curious features in these experiments which require more jected. We maythen draw another curve (Fig. 2) represent- elucidation. ing the galvanometer deflections produced when the current It has been pointed out by Warburg, and subsequently has been raised to a high value and has been subsequently by Ewing, that the area of curve 2 is a measure of the reduced to a value indicated by the abscissæ. This curve quantity of energy expended in changing the magnetism may be properly called a descending curve. In the case of the mass of iron from that produced by the current of ordinary bodies this curve is a straight line coincident in one direction to that produced by the current in the with the straight line of the ascending curve, but for iron opposite direction and back again. The energy expended is a curve such as is represented in the drawing. You with varying amplitude of magnetizing forces has been observe that this curve descends to nothing like zero when determined for iron, and also for large magnetizing forces he current is reduced to zero; and that when the current for a considerable variety of samples of steel. Different lī not only diminished to zero, but is reversed, the galvano- sorts of iron and steel differ from each other very greatly merer deflection only becomes zero when the reversed in this respect. For example, the energy lost in a comcurrent has a substantial value. This property possessed plete cycle of reversals in a sample of Whitworth's mild by magnetic bodies of retaining that which is impressed steel was about 10,000 ergs per cubic centimetre; in oil
hardened bard steel it was near 100,000 ; and in tungsten | manent magnets. The residual magnetism, o B, is then steel it was near 200,000—a range of variation of 20 to 1. practically of no interest at all; the magnetic moment It is, of course, of the greatest possible importance to depends almost entirely upon the coercive force. The kerp this quantity low in the case of armatures of dynamos, range of magnitude is somewhat greater than in the case ind in that of the cores of transformers. If the armature of the energy dissipated in a complete reversal. For of a dynamo machine be made of good iron, the loss from 'very soft iron the coercive force is 1:6 C.G.S. units ; for hysteresis may easily be less than 1 per cent ; if, how- tungsten steel, the most suitable material for magnets, it is ever, to take an extreme case, it were made of tungsten 51 in the same units. A very good guess may be made of teel, it would readily amount to 20 per cent. In the amount of coercive force in a sample of iron or steel the case of transformers and alternate-current dynamo by the form of the ascending curve, determined as I deThachines, where the number of reversals per second is scribed at first. This is readily seen by inspection of great, the loss of power by hysteresis of the iron, and the Fig. 3, which shows the curves in the cases of wrought consequent heating, become very important. The loss of iron, and steel containing o'9 per cent. of carbon. With power by hysteresis increases more rapidly than does the the wrought iron a rapid ascent of the ascending curve is induction. Hence it is not well in such machines to made, when the magnetizing force is small and the work the iron to anything like the same intensity of in- coercive force is small ; in the case of the hard steel the duction as is desirable in ordinary continuous current ascent of the curve is made with a larger magnetizing machines. The quantity O A, when measured in proper current, and the coercive force is large. There is one UDITS, as already explained-that is to say, the reversed curious feature shown in the curve for hard steel which magnetic force, which just suffices to reduce the induction may, so far as I know, be observed in all magnetizable as measured by the kick on the galvanometer to nothing substances: the ascending curve twice cuts the descendafter the material has been submitted to a very great ing curve, as at M and n. This peculiarity was, so far as magnetizing force—is called the "coercive force," giving I know, first observed by Prof. G. Wiedemann. a definite meaning to a term which has long been used in I have already called emphatic attention to the fact a somewhat indefinite sense. The quantity is really the that magnetic substances are enormously magnetic, and important one in judging the magnetism of short per that non-magnetic substances are hardly at all magnetic :
there is between the two classes no intermediate class. to imagine manganese steel broken up into small par The magnetic property of iron is exceedingly easily des- ticles, as these particles became smaller there would : troyed. If iron be alloyed with 12 per cent. of man- length arrive a point at which the iron and the manganese ganese, the kick on the galvanometer which the material would be entirely separated from each other: when this will give, if made into a ring, is only about 25 per cent. point is reached the particles of iron are non-magnetic greater than is the case with the most completely non- By the magnetic molecule of the substance we mean tha magnetic material, instead of being some hundreds of smallest part which has all the magnetic properties of the times as great, as would be the case with iron. Further, mass. The magnetic molecule must be big enough with this manganese steel, the kick on the galvanometer contain its proportion of manganese. In iron, then, is strictly proportional to the magnetizing current in the must have a collection of particles of such magnitude the primary, and the material shows no sign of hysteresis. it would be possible for the manganese to enter into eact In short, all its properties would be fully accounted for if of them, to constitute an element of the magnet. Mzwe supposed that manganese steel consisted of a perfectly ganese is, so far as I know, a non-magnetic element non-magnetic material, with a small percentage of metallic Smaller proportions of manganese reduce the magie iron mechanically admixed therewith. Thus
the property property in a somewhat less degree, the reduction bees of non-magnetizability of manganese steel is an excellent greater as the quantity of manganese is greater, proof of the fact—which is also shown by the non-mag- appeared very possible that the non-magnetic propers netic properties of most compounds of iron—that the of manganese steel was due to the coercive force being property appertains to the molecule, and not to the atom ; very great-that, in fact, in all experiments we were am or, to 'put it in another way, suppose that we were on that part of the magnetization curve below the rapiz
rise, and that if the steel were submitted to greater forces / substance by dividing the induction for any given forte it would presently prove to be magnetic, like other kinds in the ratio of the whole volume to the volume of magnetic of steel." Prof. Ewing, however, has submitted man- substance. If, on the other hand, it is as in Fig. 5-srich ganese steel to very great forces indeed, and finds that a very short axis in the direction of the force, and a long its magnetism is always proportional to the magnetizing axis perpendicular thereto-we can equally construct the force.
curve of magnetization. This is done in Fig. 6, which No single body is known having the property of shows the curve when nine-tenths of the material is highly capacity for magnetism in a degree which is neither very magnetic iron, arranged as in Fig. 5, whilst the other curse great nor very small, but intermediate between the two of the same figure is that when only one-tenth is magnetic, extremes. We can, however, mix magnetic and non- but arranged as in Fig. 4. You observe how very different magnetic substances to form bodies apparently inter- is the character of the curve-a difference which is reduced mediate. It is, therefore, interesting to consider what by the much less proportion of magnetic material in the the properties might be of such a mixture. It depends mixture in the one case than in the other. One peculiarity quite as much on the way in which the magnetic part is of these arrangements of the two materials in relation to arranged in the mass, as on its actual quantity. Suppose, each other is, that the resulting material is not isotropic : for example, it is arranged as in Fig. 4-in threads or that is, its properties are not the same in all directions, but plates having a very long axis in the direction of the depend upon the direction of the magnetizing force in the magnetizing force-we may at once determine the curve material. Of course, this is not at all a probable arrange of magnetization of the mixture from that of the magnetic ment but it is instructive in showing the character of the