usual to begin with those parts of the subject in which the idea of change, though implicitly involved in the very conception of force, is not explicitly developed so as to bring into view the different configurations successively assumed by the system. For this reason, the first place has generally been assigned to the doctrine of the equilibrium of forces and the equivalence of systems of forces. The science of pure statics, as thus set forth, is conversant with the relations of forces and of systems of forces to each other, and takes no account of the nature of the material systems to which they may be applied, or whether these systems are at rest or in motion. The concrete illustrations usually given relate to systems of forces in equilibrium, acting on bodies at rest, but the equilibrium of the forces is established by reasoning which has nothing to do with the nature of the body, or with its being at rest.

The practical reason for beginning with statics seems to be that the student is not supposed capable of following the changes of configuration which take place in moving systems. He is expected, however, to be able to follow trains of reasoning about forces, the idea of which can never be acquired apart from that of motion, and which can only be thought of apart from motion by a process of abstraction.

Profs. Thomson and Tait, on the contrary, begin with kinematics, the science of mere motion considered apart from the nature of the moving body and the causes which produce its motion. This science differs from geometry only by the explicit introduction of the idea of time as a measurable quantity. (The idea of time as a mere sequence of ideas is as necessary in geometry as in every other department of thought.) Hence kinematics, as involving the smallest number of fundamental ideas, has a metaphysical precedence over statics, which involves the idea of force, which in its turn implies the idea of matter as well as that of motion.

In kinematics, the conception of displacement comes before that of velocity, which is the rate of displacement. And here we cannot but regret that the authors, one of whom at least is an ardent disciple of Hamilton, have not at once pointed out that every displacement is a vector, and taken the opportunity of explaining the addition of vectors as a process, which, applied primarily to displacements, is equally applicable to velocities, or the rates of change of displacement, and to accelerations, or the rates of change of velocities. For it is only in this way that the method of Newton, to which we are glad to see that our authors have reverted, can be fully understood, and the "parallelogram of forces" deduced from the "parallelogram of velocities." Another conception of Hamilton's, however, that of the holograph, is carly introduced and employed with great effect. The fundamental idea of the hodograph is the same as that of vectors in general. The velocity of a body, being a vector, is defined by its magnitude and direction, so that velocities may be represented by straight lines, and these straight lines may be moved parallel to themselves into whatever position is most suitable for exhibiting their geometrical relations, as for instance in the hodograph they are all drawn from one point. The same idea is made use of in the theorems of the "triangle" and the "polygon" of forces, and in the more general method of

diagrams of stress," in which the lines which represent the stresses are drawn, not in the positions in which they actually exist, but in those positions which most fully exhibit their geometrical relations. We are sorry that a certain amount of slight is thrown on these methods in § 411, where a different proposition is called the true triangle of forces.

It is when a writer proceeds to set forth the first principle of dynamics that his true character as a sound thinker or otherwise becomes conspicuous. And here we are glad to see that the authors follow Newton, whose Leges Motûs, more perhaps than any other part of his great work, exhibit the unimproveable completeness of that mind without a flaw.

We would particularly recommend to writers on philosophy, first to deduce from the best philosophical data at their command a definition of equal intervals of time, and then to turn to § 212, where such a definition is given as a logical conversion of Newton's First Law.

But it is in the exposition of the Third Law, which affirms that the actions between bodies are mutual, that our authors have brought to light a doctrine, which, though clearly stated by Newton, remained unknown to generations of students and commentators, and even when acknowledged by the whole scientific world was not known to be contained in a paragraph of the Principia till it was pointed out by our authors in an article on "Energy" in Good Words, October 1862.

Our limits forbid us from following the authors as they carry the student through the theories of varying action, kinetic force, electric images, and elastic solids. We can only express our sympathy with the efforts of men, thoroughly conversant with all that mathematicians have achieved, to divest scientific truths of that symbolic language in which the mathematicians have left them, and to clothe them in words, developed by legitimate methods from our mother tongue, but rendered precise by clear definitions, and familiar by well-rounded statements.

Mathematicians may flatter themselves that they possess new ideas which mere human language is as yet unable to express. Let them make the effort to express these ideas in appropriate words without the aid of symbols, and if they succeed they will not only lay us laymen under a lasting obligation, but, we venture to sɩy, they will find themselves very much enlightened during the process, and will even be doubtful whether the ideas as expressed in symbols had ever quite found their way out of the equations into their minds.

TYNDALL'S FORMS OF WATER The forms of Water in Clouds and Rivers, Ice, and Glaciers. By John Tyndall, LL.D., F.R.S. (London: H. S. King & Co.)

WHATEVER comes from Dr. Tyndall's pen is sure to be vivid and clear. The present little volume forms no exception to this rule. It seems to have been composed partly in the form of popular lectures and partly as a sort of journal of a visit last year to the author's favourite holiday haunts among the Swiss glaciers. Very readable, it nevertheless betrays this composite origin, and wears more the aspect of a piece of book-making than

probably its author himself could have wished. A wrong impression of the subject is created by the title, which though singularly happy in itself does not fairly describe the contents of the book. Such a title suggests an accurate and luminous discussion of the phenomena of evaporation and condensation, the growth and movements and disappearances of mists and clouds, the formation and distribution of rain and the laws regulating the rainfall over the globe, the meaning of frost, the birth and history of hail and snow, the circulation of water over the land with the ways and workings of brook, stream, and river, from mountain-peak to sea-shore, the architecture and the functions of snow-fields, glaciers, and icebergs-in short a kind of scientific poem, dedicated to the glory of that grand old element-water. Dr. Tyndall could write such a poem better than most men, and indeed it was with the expectation that he had attempted it that we opened this last volume of his. Out of the 192 pages 28 are devoted to clouds, rains, rivers, waves of light and heat, oceanic distillation and mountain condensers. The rest treat wholly of ice. So that if we may judge by the relative space devoted to the different forms of water, ice must be six times more important than all the rest put together. A less ambitious title, such as its author could readily suggest, descriptive of the fact that the book is a record of work, intellectual and corporeal, among the Swiss glaciers, would prevent the feeling of disappointment with which many a reader has no doubt come to the last page.

Dr. Tyndall did not intend, we suppose, that his book should be regarded in any other light than as a popular exposition of his subject, and would probably disclaim any place for it as a contribution of new facts and reasonings to our knowledge of glaciers. His narratives of last year's climbings and observations read very much like those of older ones with which he has already made us familiar. They are pleasantly written, and will convey to a reader, who has never seen a glacier, a picturesque notion of what he has missed. But surely it was not necessary to rake up again the Forbes-Rendu controversy, nor to renew the claims of Agassiz and Guyot. We could have wished, too, that while alluding to Mr. Mathews and other recent observers on ice-structure the writer had taken some notice of the attack upon his own theory by Canon Mosely and Mr. Croll.

OUR BOOK SHELF

Die Anwendung Des Spectralapparate von Dr. K. Vicrordt. (Tübingen: H. Laupp, 1873.)

DR. VIERORDT has been endeavouring to found a quantitative spectrum analysis for bodies giving an absorption spectrum. His method consists in the use of a slit divided horizontally into two parts; one of these is adjusted to a certain width; the solution whose absorption is to be examined is placed opposite this, and in front of the other half is placed another solution of the same body but of a different strength, and the slit is then narrowed or widened as the solution is stronger or weaker until the absorption is the same in both halves of the spectrum. The width of the latter slit is then read off. By using a number of solutions of strengths varying decimally from the weakest possible to the strongest through which light will pass, curves are obtained and a solution of unknown strength can then be interpolated in the curve and its

value ascertained. The solutions to be examined are, of of course, kept at a constant thickness. As the relation between the concentration of the solution and its coefficient of the absorption of light only remains constant within certain limits, solutions of the necessary dilution have to be employed and unknown solutions must be diluted to this point: the value is then found by calculation.

Tables for calculations of various kinds required are given, and the memoir is illustrated with lithographs of the working details of the divided slit. A number of specimen curves are also given. The memoir is well worthy the attention of all who have to estimate the strength of colouring matter.

LETTERS TO THE EDITOR

[The Editor does not hold himself responsible for opinions expressed by his correspondents. No notice is taken of anonymous communications.]

Existence of Man in the Miocene

I HAVE received a letter from Mr. Edmund Calvert, in which he informs me that his brother, Mr. Frank Calvert, has recently discovered, near the Dardanelles, what he regards as conclusive evidence of the existence of man during the Miocene period. Mr. Calvert had previously sent me some drawings of bones and shells from the strata in question, which Mr. Busk and Mr. Gwyn Jeffreys were good enough to examine for me. He has now met with a fragment of a bone, probably belonging either to the Dinotherium or a Mastodon, on the convex side of which is engraved a representation of a horned quadruped, "with arched neck, lozenge-shaped chest, long body, straight fore legs, and broad feet." There are also, he says, traces of seven or eight other figures, which, however, are nearly obliterated. He informs me that in the same stratum he has also found a fl nt flake, and several bones broken as if for the extraction of

marrow.

This discovery would not only prove the existence of man in Miocene times, but of man who had already made some progress, at least, in art. Mr. Calvert assures me that he feels no doubt whatever as to the geological age of the stratum from which these specimens were obtained.

Of course I am not in a position myself to express any opinion on the subject; but I am sure that the statements of so competent an observer as Mr. Calvert will interest your readers. High Elms, March 23 JOHN LUBBOCK

Adaptation to External Conditions

THE curious modification of adaptation to external conditions in the case of the Salamandra atra, which I have more than once brought under the notice of naturalists, but which I myself first noticed under the direction of Prof. von Siebold, has been cited by Mr. Darwin ("Origin of Species," 4th Ed. p. 534) in confirmation of his views. I revert to it now for the sake of its illustration of a new and striking observation, which has excited the incredulity of several eminent naturalists in France-an incredulity, we may suppose, founded on their ignorance of the previous observation." The fact to which I called attention was this: The ordinary salamander, or Newt, is born in the water as a tadpole, and in the water it completes its metamorphosis. But the Salamandra atra, living high up in the mountains, with no pools in which to pass its tadpole existence, is born on the land, a completely formed animal; that is to say it passes through the tadpole stage while still within its mother's body. placed it in water, wherein it swam as if that were its natal eleI have taken it from the gravid female in this tadpole state, and

ment.

In the Revue Scientifique, No. 37, there has just appeared a brief account of some observations made by M. Baray at Guadeloupe, from which it appears that the frogs, having in that volcanic island no marshes nor pools suitable for the early tadpoles, have adapted themselves to these conditions by passing through

all the tadpole stages of metamorphosis while still in the egg. All these stages have been observed by M. Baray; and whoever is familiar with the evolution of the ordinary tadpole before it quits the egg, will see that M. Baray has observed only a modified form of the well-known process. The Guadeloupe frog is born as a frog, not as a tadpole; and this, paradoxical as it may seem to some naturalists who cannot dismiss traditional conceptions, is even less remarkable than the case of the Salamandra atra, because it is only an extension of the period of incubation, whereas with the salamander it is the substitution of viviparity for oviparity. How the presence of water leads to an acceleration of the birth, or the absence of water leads to its retardation, is an interesting point for investigation; whether retarded or accelerated, the finally-acquired structure is the same. The Priory, March 22 GEORGE HENRY LEWES

Anticipations of Natural Philosophy,

MAUPERTUIS

HAVING lately had occasion to examine the works of Maupertuis I, like Prof. Jevons, was struck by meeting with anticipatory glimpses of the modern theory of Natural Selection. The passage, given almost word for word by Lord Bolingbroke in the quotation made by Prof. Jevons, occurs somewhat incidentally in two parts of Maupertuis' writings; in the memoir alluded to ("Les Loix du Mouvement et du Repos, déduites d'un principe métaphysique"); and in the "Essay de Cosmologie," into which the memoir was expanded five years later (1751). In both these works Maupertuis is chiefly concerned with establishing his well known metaphysico-mechanical principle of "The Least Action" ("La moindre Quantité d'Action"); and with deducing therefrom proof of the existence of God. But the doctrine of "The Survival of the Fittest" is more clearly discernible, and more than incidentally referred to, in his small physiological treatise, "Venus physique" (Euvres, tome ii. ed. 1756). The whole of this work is not wanting in interest, but as bearing specially on the subject in question, I would mention the third, fifth, and last chapters of the second part. Chapter III. is entitled "Production de nouvelles especes." In it the most pronounced passage is perhaps the following: "Mais la sage Nature, par le dégoût qu'elle a inspiré pour ces défauts, n'a pas voulu qu'ils se perpetuassent; chaque père, chaque mère fait de son mieux pour les éteindre; les beautés sont plus sûrement héréditaires; la taille, et la jambe, que nous admirons, sont l'ouvrage de plusieurs générations, où l'on s'est appliqué à les former." Chapter V., called an Essay d'explication des phénomènes précédents," is an attempt to explain the physiological processes at work in the preservation of the best types, and in the production of new forms. On the efficacy of these processes the author says: "L'expérience pourroit, peut-être, éclaircir ce point; si l'on essayoit pendant longtemps de mutiler quelques animaux de génération en génération, peut-être verroiton les parties rétranchées, diminuer peu à peu; peut être verroit-on les à la fin s'anéantir." The last chapter contains a summary of the whole work, and a number of "Doules et Questions," propounded by the author. In one of these he asks, "Cet instinct des animaux, qui leur fait rechercher ce qui leur convient, et fuir ce qui leur nuit, n'appartient-il point aux plus petites parties dont l'animal est formé?" In another question Maupertuis puts forward a bold hypothesis as to the influence which the decomposed material of the dead animal organism might exercise upon plants, and through them upon the structure and character of the living organism.

In his Système de la Nature also (Euvres, tom. ii. ed. 1756), Maupertuis combats the special creation theory of the origin of species, and advocates a doctrine, which may be called Natural Selection, the selective principle being placed in the ultimate elements of both organic and inorganic substances, of which elements "la perception est une propriété essentielle," and which "doués d'intelligence s'arrangent et s'unissent pour remplir les vues du Créateur."

Such are a few of the glimpses to be met with in the French philosopher, of the modern doctrine of Darwin and Spencer. Similar ones may not improbably be found elsewhere, but such "resultless tendencies," as the course of events has proved them to be, can in no degree detract from the merit and originality of those who have made of Natural Selection a well-substantiated and homogeneous theory. W. H. BREWER

Grace's Road, Camberwell, March 10

EMPEDOCLES

ON reading Prof. W. Stanley Jevons' interesting letter in this week's NATURE, I referred to my note-book, and found the following quotation, under the title of "Natural Selection," which shows that the opinion of Maupertuis is at least as old as d'Empedocle sur la production des animaux par des causes acciEmpedocles." Cette dernière opinion sert á expliquer les idées dentelles. L'attraction et la répulsion des élémens donnèrent naissance dans les commencemens et par le seul effet du hasard, à des têtes sans cou, à des jambes sans corps, à des animaux moitié boeufs et moitié hommes, en un mot, à une foule de monstrés semblances. Parmi tous ces êtres, les uns étaient construits de manière qu'ils semblaient êtres doués de l'intelligence: ceux-là conservèrent la vie, et propagèrent leur espèce, mais ceux auxquels l'organe de la vie manquait, retombèrent dans le chaos, d'où ils étaient sortis.” ("Histoire de la Medecine," par Kurt Sprengel, vol. i. p. 249.) Sprengel gives the following references :-Aristotle, Physic. Lib. ii, c. 4, p. 465., c. 8, p. 470. Owing to my distance from a public library I have not hitherto had an opport inity of referring to Aristotle; but as Prof. Jevons is more favourably circumstanced, I hope he will consult the original, and if he finds anything which throws further light upon this interesting question, that he will report it to your readers.

Although, as Prof. Jevons remarks, the introduction of the notion of chance is erroneous, the speculation shows how thoroughly the Greek Atomists had banished from their explanations of phenomena all reference to first and final causes, anticipating in this respect the modern conception of science. I cannot deny myself the pleasure of quoting the weighty judgment of Bacon upon this point:" And therefore the natural philosophies of Democritus and others," says Bacon, "who allow no God or mind in the frame of things, but attribute the structure of the universe to infinite essays and trials of nature, or what they call fate or cessity of matter without any intermixture of final causes, seem, fortune, and assigned the causes of particular things to the neso far as we can judge from the remains of their philosophy, much more solid, and to have gone deeper into nature, with regard to physical causes, than the philosophy of Aristotle or Plato; and this only because they never meddled with final causes, which the others were perpetually inculcating." (Advancement of Learning, Book iii. chap. iv.) Waterfoot, March 8

ARISTOTLE

JAMES ROSS

It is interesting, as Mr. Jevons says, to observe such traces as are to be found in history of theories more or less anticipating the principle of natural selection. But if the instance he cites from Maupertuis fairly represents the last century in this matter, it is chiefly of interest as showing what a little way it is possible to travel on certain roads in twenty-two centuries: for Aristotle discusses the same theory in his "Physics" (ii. 8), and appears to attribute it to Empedocles. "It may be a question," he says, "whether physiological effects which seem to be due to final causes are not really accidental. An organism survived, we may suppose, if it happened to be as a whole constituted in a suitable manner; that is, in a manner in which it would have been constituted by design; organisms otherwise constituted perished and perish still, like the Bovyev avspóжpwpa of Empedocles." Now, except that his monsters are certainly not quite so monstrous, I do not see that the "Flattener of the Earth" gets beyond that. At any rate he lags behind Lucretius, who adopts the same theory of "discriminative destruction" (v. 837-877), but applies it, as Mr. Munro points out (on line 855), not merely to monsters but to regularly organised creatures," either not so gifted as to protect themselves or not so valuable as to be protected by man.

66

This is, as far as it goes, a theory of natural selection. It is a theory of the survival of the fit, absolutely; but not being a theory of the preponderant survival of the fitter, and not taking adequate account of inheritance, it is not a theory of evolution. Indeed, though Lucretius recognised a constant change in the conditioning circumstances, and therefore in the organisms conditioned (828-836), it was to account for the stability of species that he called in natural selection and not to give a clue to the laws of their variation. That is the direction in which there must have been most room for progress; and traces of such progress may be to be found. tried Gassendi?

Hadley, Middlesex

Has Mr. Jevons C. J. MONRO

Fossil Cryptogams *

I Do not propose at present to controvert in detail all the posi tions taken up by my friend Prof. McNab in his brief communication to your pages on "Fossil Cryptogams" (vol. vii. p. 267), because the time has not yet arrived for doing so. Much more detailed information respecting the subject which yet awaits publication must be had before it can be discussed in a satisfactory manner. I merely wish to avoid leaving the impression, by my silence, that I either admit his supposed facts or accept his inferences. When his paper, to which he refers, was read in Edinburgh, specimens of sections of Calamites of various ages were sent down by me for the purpose of being exhibited to the Botanical Society. This was done by Prof. Dickson, who at the same time expressed his preference for my views over those of Dr. McNab, as is stated in the officially published notice of the meeting in question. Since then I have received a kind letter from Dr. Balfour, who has carefully examined the specimens referred to, and who also expresses a similar conviction. I think that I have unmistakeable proof of the circumferential growth of Calamites, which Dr. Macnab denies, in specimens of large size, and in which the exogenous zone is of great thickness.

As to

Prof. Mc Vab speaks of "the moist nature of the soil in which the Calamites must have grown," as probably causing a different mode of growth in them, to that "circumferential one which he admits has probably taken place in Lepidodendra, Sigillariæ, and Dictyoxylons; but I beg to suggest that we have no reasons for thinking otherwise than that these plants grew side by side, and under precisely the same physical conditions, hence the "moist soil" of my friend is an assumption. This close association of Calamites with Sigillaria was demonstrated and commented upon by Mr. Binney many years ago. Dr. McNab further separates Lepidodendron from Sigillaria and Stigmaria, placing them in different groups. When he receives my third memoir in the Philosophical Transactions (which is printed but not yet circulated), he will see how utterly this plan of procedure is opposed to the facts. I contend that Sigillariæ are virtually Lepidodendra, and that Stigmaria is equally the root of both. the location of my old, but now abandoned genus, Dictyoxylon, the more I study it the less I feel competent to fix its true place amongst the Cryptogams. But notwithstanding Dr. McNab's idea as to its coniferous affinities, I venture to affirm, from a prolonged study of a cabinet full of specimens, that its woody axis is not one bit more exogenous than those of Calamites and of matured Lepidodendra. The fact is that whatever the vessels of these various exogenous woody zones signify, they must stand or fall together. They are either all ligneous or they are all cortical. I think that my forthcoming illustrations of the bark structures amongst the Burntisland Lepidodendra, as well as of our Lancashire specimens, will show that all the elements which Dr. McNab finds in Lycopodium Chamaecyparissus are present, in their proper places, the schlerenchyma of the hypoderm being especially well represented, yet it is precisely this hypoderm with which Dr. McNab believes my exogenous layer to correspond. There is one if not two distinct layers of cortical parenchyma between this schlerenchymatous layer and my ligneous zone, which latter is so magnificently represented in these plants.

The intimate structure of these latter layers, whether we regard the forms and arrangements of the entire woody wedges or that of their component tissues, is so identical in the two cases of Calamites and Lepidodendra, that an active imagination alone can make the one axial and ligneous, and the other cortical. Dr. McNab draws a distinction between vessels representing ("feebly ") the fibro-vascular bundles of the living Equisetums, in the Calamites, and the more external portions of each woody wedge, which he regards as representing the hypodermal schlerenchyma of Mettenius. I unhesitatingly avow that there is no ground whatever for this arbitrary separation. He is putting asunder things which have been joined together from the beginning of time. The tissues in question are as identical in their structure as they are uninterruptedly continuous in their arrangement.

Whilst I am thus opposed to Dr. McNab both on questions of fact and of inference, I feel obliged to him for calling my attention to this possible explanation of the facts, even though after a careful study of his views I feel constrained to reject them so far as the interpretation of Calamites are concerned. On the questions relating to Meristem growths, we are much

We regret that the insertion of this letter has been so long delayed in consequence of the great pressure upon our space,

nearer to mutual agreement, and I accept thankfully his admisson of the coniferous affinities of Dictyoxylon, not because I am prepared to recognise any specially close coniferous relationships, but because Dr. McNab's idea necessarily involves an admission of the existence of exogenous features in these plants; yet I contend that the Dictyoxylons are neither more coniferous nor more exogen us than most of the other Cryptogamic carboniferous stems which exhibit equally strong proofs of a similar exogenous growth. But I again repeat that we shall not be in a position to grapple philosophically with these problems until all the results of my prolonged researches are published. This is being accomplished as rapidly as my limited leisure admits of. When completed, I shall be quite prepared to enter, if necessary, and in a friendly spirit, upon the entire controversy. W. C. WILLIAMSON Owens College

Leaf Arrangement

AFTER reading Dr. Airy's paper on Phyllotaxis (NATURE, vol. vii. p. 343), I cannot see that we are at all nearer than before, any satisfactory explanation as to the inherent cause of it. Let the question be put thus:-If we can conceive, as all will admit, the possibility of leaves being scattered anyhow along a branch, why are they not so, but in some strictly mathematical order? Any disturbance in that order is usually so slight and trivial (due apparently in part to the conical nature of the axis, and unequal growth or slight twists; and which thereby cause certain leaves to assume slightly wrong positions), that it does not destroy the fact that they absolutely are arranged, and can be represented, mathematically.

In my paper on the angular divergences of the Jerusalem artichoke (Linnean Trans. vol. xxvi. p. 647), I pointed out that two questions might represent all that is required to be solved. (1) That if a leat be selected as No. 1, then No. 2 lies within a certain arc, viz. :-120°-180° from No. 1, for the ordinary series of fractions, and which it does not transgress-why is this? (2) If we allow that arc-why does the second leaf not assume any spot, but is rigidly confined to a certain angular distance from the first?

I cannot think with Dr. Airy that "the way in which all the spiral orders may have been derived from one original order [was] by means of different degrees of twist in the axis." For if we take a piece of round elastic as he describes, with balls fixed according to some spiral arrangement-say-then the successive balls will lie at an angular distance of 144°; and if No. I be fixed and we twist the indiarubber at No. 2, we may cause it to make a complet rotation if we choose.

If, now, his idea of "twist" be admitted as a vera causa of phyllotaxis, we may ask, what causes the twist to be just so much and no more as to make No. 2 pass through 9° (the angular divergence of being 135), so as to pass into the next arrangement? To say that some such point is a 'position of maximum stability" seems to me to give a fictitious importance to the idea of twist, for the expression conveys no really explanatory meaning at all.

66

Again, to admit that it does not accurately hit the right place, and is in consequence more like Nature, is equally delusive, for Nature is quite accurate enough to be represented mathematically, whereas the positions taken up by the balls must be arbitrary, or at least in proportion to the twist given by the hand-a perfectly arbitrary force? Moreover he appears to overlook the fact that if an axis becomes twisted the fibres will be twisted also, but they are not so; the elastic band he adopts would, if it were a pliant shoot, contort the vessels and wood fibres, a condition not obtaining in nature.

Nor can I agree with him in deducing all the members of the series from. My experience leads me to infer they are derived from opposite leaves, such as one finds in the cotyledons. In the Jerusalem artichoke opposite leaves are frequently succeeded by; and this is obtained by the pair of leaves, next above the strictly opposite pair, converging to one side, the next pair do so still more, when it will be found that the arrangement will be henceforth established; the internodes having become more and more developed at the same time. I strongly suspect the original arrangement to have been whorled and quincuncial. This is at least very abundant, if not universal, in coal plants. The whorls may have subsequently become reduced to fours, threes, and twos or decussate. We see this tendency to symmetrical reduction in many existing plants, eg, stamens and carpels of Crucifera: Circaa as com

pared with Epilobium; the stamens of Geranium as compared with Erodium. Where the reduction has been unsymmetrical, I suspect it has been due to insect adaptation: as in di-dynamous

s'amens.

As soon as decussate leaves are secured, then we possess the basis for all ordinary leaf-arrangements.

4 but in

Dr. Airy alludes to non-existing orders,,,, 11, the Jerusalem artichoke the secondary series 1,1,4, 11, 1's, occurs frequently, and arises from the breaking up of "tricussate" whorls in an exactly similar manner to the primary series, 1, , &c., arising out of opposite leaves. On the other hand spirals do not easily, if ever, return to whorls. If any one will notice how curiously the above is executed in the Jerusalem artichoke, he will see that there is evidently some power at work in the plant which, as it were, compels the spiral to form, and to form mathematically, will be convinced, I am sure, that a “twist is very far from being the cause-there being none whatever in the cases mentioned above: and further, when whorls break up, the leaves are at first quite irregular, but they gradually "right them elves," acquire the proper angular divergence, and then form some member of the spiral arrangements to perfection. GEORGE HENSLOW

Flight of Projectiles

IN reply to the letter of "W. Hope," in NATURE of March 13, I request permission to state that by a simple formula, I meant one that would be easily understood. I did not intend

the word simple to be taken stric'ly in its mathema'ical sense. It is easy for Mr. Hope to employ symbols to represent the initial velocity, angle of elevation, or any other additional particular he may consider necessary for the solution of my problem.

No one possessing the most elementary knowledge of the theory of projectiles can be ignorant of the disturbing elemen's to which your correspondent refers, or of others to which he makes no allusion. But these cannot be accurately estimated, and, therefore, must necessarily be neglected in a theoretical investigation. I do not an'icipate that they will be found to vitiate the results of theory to the extent Mr. Hope supposes. In the practical application of the formula for which I have asked, the numerical values of the general symbols, would be the mean of carefully conducted experiments. Thus the trifling variations arising from slight differences in the charge, the amount of fouling, or other causes, would be reduced to a minimum. The variations in the force and d rection of the wind would often neutralise each other. For these reasons I cannot

agree with Mr. Hope in thinking that the calculation would be either "useless or deluding," on the contrary I believe it would be valuable as indicating a mean deflection, about which the experimental deflections would be found to group themselves. Of one thing I am certain, that it would enable us to bring home to the soldier the great effect of wind in deflecting the bullet, and perhaps it might assist us in dispelling the notion of absurdity which is inseparably associated in his mind with the effort to bit something by aiming at nothing. In accomplishing this one of the greatest obstacles to the development of skill in rifle-shooting would be removed.

If Mr. Hope will kindly supply me with the formula which I have asked for, I can assure him that however lightly he may appreciate the results of his labours, by me, at least, they will be valued, and, I venture to hope, made practically useful. Surely he cannot be in carnest in denouncing all theory which approximates to, but does not exactly accord with practice, as science, or pedantry." If this dictum be sound, I can only say it would be easy to show that a great deal of the science of our day, gunnery science in ular, is spurious.

「

"bastard

rity, did not consider my problem he Cours Elementaire De Balish I regret is rather too comimagine that he would be the afford more than a rough Hence I conclude that efit of the French army,

General Didion, a l' unworthy of investigat. tique, he has given a sol. plicated for my purpose. last person to expect his approximation to the results in publishing his calculation f he could have had no conceptic science, or pedantry," and must "mischievous unpractical pedant

ROBE

e.

School of Musketry, Hythe, Marc. 17

science was "bastard en unconscious what a

EID, Sergeant Major

Deep Sea Soundings near the Equator

"Our Casella-Miller deep-sea thermometer worked admirably. This beautiful instrument stood the test at a depth of 2,040 fathoms, two miles north of the Equator, in longitude 22° 16′ W., when it indicated a temperature of 35° F. ; at 1,000 fathoms 38°; at 400 fathoms 41°; at 300 fathoms 44°; at the surface 81°; in the air 80°.

"On our track from the Canary Islands to Rio we found the temperatures at uniform depths to vary about 2°. Our specimens of the bo tom from the volcanic region differ in every respect from those obtained in other parts of the ocean."

SURVIVAL OF THE FITTEST

THE 'HE doctrine of the "survival of the fittest" must be The strangely understood in some quarters. American papers report Prof. Agassiz as having expressed himself in this wise at a recent meeting of the Massachusetts State Board of Agriculture, of which he is a member :- "I do not know how animals originated; a brilliant imagination that of Darwin; a very necessary faculty in the scientist. The sense I know too well to misquote him. Hasty generalising of observation is Darwin all over. Natural selection is out of generation. Natural necessity, what is it? Do we find that only the strong beget families? Observe plants at the foot of the White mountains, where are large trees, and so up to the summit, where they are mere shrubs. The weak may and do survive as well as the strong. Ignorance lies at the base of the discussion."

Probably no one naturalist, however eminent, can be expected to know everything, or even all simple things. Can it be possible that Prof. Agassiz supposes (as his argument seems to require) that the dwarf trees in question grow and survive near the top of the mountain, notwithstanding they are not the fittest, rather than because they are the fittest, for the conditions? And does

he conceive the doctrine of natural selection to be founded upon some idea of an abstract fitness, irrespective of the conditions, and not upon the survival of the fittest under and in consequence of the conditions? Surely the argument brought against the doctrine is a good illustration in its favour, only an extremely simple and elementary one.

We never could quite comprehend why Prof. Agassiz should give himself so heartily and persistently to the work of demolishing the doctrine of the derivation of species, in all its forms, considering how large and honourable a part he has himself taken in laying the built. Of these foundations none is stronger than the foundation upon which the modern doctrine has been capital one, generally supposed to be established by him, that the succession of species in time corresponds mainly with that in systematic rank, and is also somehow paralleled in the development of each individual of the higher ranks. So that, in view of his continued but unsuccessful efforts to drive the incoming doctrine out of the land, we could imagine him addressing his own important discoveries in the words used by Balak to Balaam : "What hast thou done unto me? I took thee to curse mine enemies, and behoid, thou hast blessed them altogether."

SUB-WEALDEN

EXPLORATION.—SECOND QUARTERLY REPORT

AFRESH survey of the Lower Wealden beds in eastern