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therefore have been there as larvæ from the beginning. The claim that the borax killed eggs is then untenable.

There is no information as to the number of maggots in the manure to start with, the temperature of the manure (a very important point), or the comparative temperatures of each lot. Practically, the book depends on one experiment, carried out under doubtful conditions and contrary to much larger experiments made here. We regret it, as it will mislead many, and lead to much useless employment of borax.

1

(2) The second volume is an attempt to get people to realise that the house fly is a real danger and to persuade them to cope with it. "Knowledge is power only when it is turned to practical use" is the opening to chapter vii., and we could quote other sentences full of meaning that occur in it.

The remedies advocated in it are usually sound and practical. Like others, the author fails to realise that the fly maggots live in material that is actually fermenting and in manure heaps that are hot, and that in consequence a purely superficial treatment will often kill them. It is also not true to say that "an insecticide to kill maggots must be about four or five times as strong as that used against other kinds of insects": it must be different, that is all.

The various chemical treatments recommended (salt, sodium arsenate, Paris green, sulphate of iron, etc.) are not practical for manure, nor are they cheap, and it would be interesting to know exactly what evidence there is of their effective

ness.

Apart from this, the reader will find the book sound and helpful. It is written for South Africa, and all the methods advocated would not suit this country.

A chapter is devoted to the stable fly, which is possibly a disseminator of infantile paralysis. This chapter has special value now in England, as the stable fly is sometimes the only fly common in seaside resorts where children swarm, and most people, quite naturally, do not differentiate it from the house fly. When these matters are more fully investigated the importance of the stable fly will be settled. Meanwhile it is worth remembering that when people think that the house flies are biting them, in autumn, it is really the stable fly.

Of the two volumes we prefer the second, and we know of no other volume that is quite so simple, sensible, and practical. To those who wish to realise what the fly is, or does, without unnecessary scientific details, we commend this little book.

H. M. L.

OUR BOOKshelf.

A Descriptive Monograph of Japanese Asteroidea, Part I. (Journal of the College of Science, Imperial University of Tokyo. Vol. xxix., Art. i. December 17th.) Pp. 808+ xix plates. (Tokyo: The University, 1914.)

The

In this large volume of about 800 pages only the Phanerozonia of Japan are included. Fifty-nine species are described, of which eighteen are new. The descriptions, in the case of thirty-nine species, are based on on an examination of a number of collections preserved in various Japanese Institutions; but in the case of twenty species, which are not represented in any of the indigenous collections, either the extant description of the original author is quoted, or the species is very honestly expounded in a series of extracts from the several authors, who at different times have discussed and criticised it, in such a way that its definement suffers no perdition. autoptical descriptions are excellent: they are clear and discriminative, and though rather tending to be meticulous, are far from being tedious or discursive. But in dealing with the history and literature of the subject the author is inclined not only to a redundance of quotation which is largely iterative, but also to burdening the quotations with a superfluity of their unimportant detail. Seeing that there is provided an exhaustive bibliography, filling over 100 pages. and concerned exclusively with papers cited in the text, this multiplication of undigested extracts descriptive of one and the same species is wearisome and unnecessary, though, of course, there are some who would not regard this feature as in any way a defect. On the whole, however, it must be allowed that this monograph is a wonderful piece of solid, honest work, the very card and calendar of taxonomy, and fit to stand among zoological works of reference of the very highest class. The typography is excellent, and there are nineteen double plates of admirable illustrations in photogravure.

In the copy under review pp. 81 to 86, which would appear to relate to Ctenodiscus crispatus, are wanting, and in their place pp. 97 to 112 are duplicated.

The Health of the Child: A Manual for Mothers and Nurses. By Dr. O. Hildesheim. Pp. xii + III. (London: Methuen and Co., Ltd., 1915.) Price Is. net.

THE introduction to this work is written by Dr. G. F. Stell, the well-known Professor of Diseases he praises it, it is a work of supererogation of a of Children at King's College Hospital, and when mere reviewer to say ditto. The feeding, clothing, washing, nursing, and early education of the infant are all treated with admirable clearness and sound common-sense. The underlying doctrine that cleanliness and godliness are akin, if not The book identical, is forcibly pressed home. may not only be placed safely in the hands of every mother and nurse, but it seems almost unsafe to allow any mother and nurse to be without this excellent shillingsworth. W. D. H.

LETTERS TO THE EDITOR.

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

The Analogy between Radicles and Elements. THE remarkable chemical analogy of the ammonium radicle and the alkali metals may be explained with the help of Bohr's theory of atomic structure. According to Bohr, the atom of nitrogen consists of a nucleus with a positive charge of 7e, surrounded by two rings of electrons, the inner containing 4, the outer 3 electrons. N is, therefore, represented by 7 (4,3). Ordinary chemical compounds are supposed to be held together by rings of electrons rotating in planes perpendicular to the lines connecting the nuclei of the composing atoms; so that NH, may be represented by (4, 3-3). This principle leads, however, to difficulties, if applied to NH; a configuration (4, 3-4) seems impossible. It is better to suppose the nuclei and electrons to rearrange themselves within the atom. I assume, therefore, that the nuclei unite, or at least that they get quite close to each other, in the centre of the system, while the electrons arrange themselves in four rings (4, 4, 2, 1), rotating round the joined nuclei. It may seem difficult to bring the nuclei together against the repelling forces, but it must be remembered that the radicle NH, can only be formed by indirect methods; in no circumstances will ammonia and hydrogen unite to form NH1. The co-operation of another molecule containing hydrogen, like H2O, HCl, is absolutely necessary, an intermediate compound first being formed, from which the ammonium-ion is produced by electrolytic dissociation. Once liberated, the ammonium decomposes immediately; it is extremely unstable, exactly conforming to our expectations. It is also important to remark in this connection, that, according to Coehn, electric charges are given off during the decomposition.

The arrangement proposed at once shows analogies with Bohr's representation of Na (8, 2, 1) and K (8, 8, 2, 1). These two configurations contain the same outer rings as NH, and differ only with regard to the inner rings. The number of electrons in Na and NH, is even the same; in K and NH, we find the same number of rings. The second similarity seems to be of primary importance, ammonium resembling potassium more closely than sodium. The fact that the analogy does not go further than the chemical properties follows at once from the general principle that the chemical character of a substance depends only on the outer rings.

The

The same considerations apply, of course, to PH,, which, however, is only known as an ion, and AsH,, and perhaps to hydrazine, which shows some resemblance to calcium. Whether the substituted ammonium bases may also be drawn within their scope is not yet settled.

There is still another line of thought to which I wish to direct attention. In the periodic table nitrogen is placed in the fifth group. When it combines with four hydrogen atoms, according to the above hypothesis, the nucleus charge increases by 4e; the resulting radicle is analogous to a metal of the first group, i.e. to an element which occupies the fourth place on the right of the original element. This is exactly the reverse of the radio-active transformations in which by the loss of an a particle (2e) the atom removes two places to the left.

This idea may also be applied to the analogous sulphur and iodine bases. Although these are only known |

in compounds, in which the hydrogen atoms are substituted by aliphatic or aromatic radicles, we shall take for discussion the fundamental types; instead of SR,OH and IR,OH, we consider the radicles SH, and IH. SH, also has the chemical properties of an alkali metal. Now, sulphur is placed in the sixth. group; if the nucleus takes up three elementary charges, 3e, the atom shifts its position by three places to the right, and arrives in the first group, thus confirming the general law. Also, the change of the iodine atom (seventh group) by taking up two hydrogen atoms, 2e, is an agreement with the theory, for the iodonium radicle also exhibits the properties of a strong base. Iodonium, it is true, especially resembles thallium, but it is known that thallium and silver are closely similar; so iodonium also fits in the first group.

The above considerations may be extended to resemblance. Though cyanogen is not unstable, it is cyanogen and the halogens, which also show a striking high temperatures, and in the presence of alkalis, or not easily obtained. Its formation is only possible at by the use of electric discharges. It is a strongly endothermic compound. The structure of the CN radicle may be represented by 13 (4, 4, 4, 1), whilst Bohr writes fluorine 9 (4, 4, 1), and chlorine 17 (8, 4, 4, 1). E. H. BUCHNER. Chemical Laboratory, University of Amsterdam, July, 1915.

1

The Density of Molecules in Interstellar Space. IN recent years evidence has been brought forward by several investigators indicating that light from distant stars suffers a slight attenuation in travelling through interstellar space. In particular a recent investigation by Jones2 assigns fairly definite numerical values to coefficients of attenuation corresponding to "photographic" and "visual" light from stars of known proper motions and spectral types the magnitudes of which had been carefully measured by Parkhurst for light of these wave-lengths. If, as seems reasonable, this extinction is assumed to be due to attenuation by scattering in travelling through a "residual" gas occupying interstellar space, we are enabled to estimate the average density of molecules in the intervening regions, following a method due originally to Larmor for assigning an upper limit to the density of matter in comets' tails.

If we denote by the coefficient of attenuation corresponding to wave-length A, radiation of this wave-length originally of intensity E, is reduced, after travelling a distance x, to the value given by E=Ee- According to Rayleigh's law of molecular scattering, K is given in terms of the refractive index, and the molecular density of the medium n by the relation к=3(μ2 −1)2λ-^n. The ability of Rayleigh's law to account almost completely for the attenuation of solar radiation in travelling through the earth's atmosphere was first pointed out by Schuster; a later investigation by the writer," based on the results of the Smithsonian Astrophysical Observatory, indicated that formulæ based on this law were competent to explain atmospheric extinction as well as to account quantitatively and qualitatively

1 Kapteyn, J. C.. Astrophysical Journal, xxix, (1909), DD. 46-54: xxx. (rcog), pp. 284-317 and correction p. 308. Turner, H. H., Monthly Notices Roy. Ast. Soc., Ixix. (100). p. 61. King, E. S., Harvard Annals, lix., No. 6, p. 179, April, 1011: Harvard Annals, lxxvi,, No. 1, pp. 1-10. 1913. Brown, F. G., Monthly Netices, Ixxii. (1912), D. 195, also p. 718.

2 Jones, H. S., Monthly Notices Rov. Ast. Soc, xxv (1914), pp. 4-16.

3 Parkhurst. J. A., "Yerkes Actinometry," Astrophysical Journal, xxxvi. (1912), p 160.

Larmor, Sir J.. Lectures, Cambridge, 1908.

5 Schuster, A, NATURE, July 22, 1909; "Optics," 2nd Edition, 1909. p. 320.

King, L. V., Phil. Trans. Roy. Soc., ccxii.A (1912), PP. 375-433

for the intensity and distribution of sky-radiation as far as the observations available at that time could be tested. As a final test, the Smithsonian results were reduced with a view to obtaining a value for the number of molecules per cm.3 of a gas at standard temperature and pressure; the result obtained by the writer,' n。=(2·78 ± 0·01) × 101, and a later independent determination by Fowle, n,=(2.70±0.02) × 1019, indicate that we may rely with confidence on Rayleigh's law in dealing with molecular extinction for wavelengths not too close to regions of selective absorption. In dealing with attenuation in a stellar distance x=A, the term KA is so small that we may write to sufficient degree of approximation KA=(E,-E)/E., i.e. KA is the proportional loss of intensity in travelling a distance A. Denoting by KA and A the proportional losses of intensities corresponding to " * photographic" and "visual" light of average wave-lengths A and A2 respectively, we derive on reducing to intensities the result obtained by Jones,' [(photographic) – (visual)] losses = +0.00473 ± 0.00035 magnitude, the relation (K-K2)=0.00435 ± 0.00032, the distance ▲ being 10 parsecs (1 parsec = distance corresponding to a stellar parallax of 1"3.26 light-years=3.08 × 1019 cm.). If it is assumed that the extinction is brought about solely by molecular scattering, we also have the additional equation K1/K2 = (A2/A,)*.

Unfortunately, it is somewhat difficult to assign with accuracy the average wave-lengths corresponding to "photographic" and "visual" light. A rough estimate by the writer from Parkhurst's curves of spectral intensities corresponding to the plates and filters employed in the photographic and visual determinations yielded the values A,=0.446 and λ=0·533μ, so that we obtain K1/K2=2.08, giving K,A=0.0083, and K2A=0·00403.10 In order to realise more vividly the extremely small attenuation which these numbers represent, it is easily verified that in order to lose onetenth of its original intensity radiation of these wavelengths must travel for about 41 and 8.5 centuries respectively.

For the purposes of the present discussion we assume hydrogen to be the constituent of interstellar space (until we know more about the physical properties of "coronium," "nebulium," or other primordial gases which might possibly occupy these regions). Taking μ-1=0.000140, n=2.78 x 1019, λ=446 × 10-5 cm., we easily derive for the coefficient of attenuation in hydrogen at standard temperature and pressure the value = 5.89 × 10-8 cm. -1. For this wave-length in interstellar space we have K=2.72 × 10-22 cm.-1, SO that n/nK/K1 = 4.62 x 10-15, giving finally for the molecular density in interstellar space the estimate n=128 × 105 hydrogen molecules per cm3. 10

11

Associated with the problem of attenuation by scattering is that of calculating the amount of starlight scattered by the molecules of interstellar gas. In this way might be explained the extremely faint luminosity which several observers believe to exist over the background of the sky. This scattered light might also account for discrepancies which have been 7 King, L. V., NATURE. xciii. (July 30, 1914), pp. 557-559. Fowle, F. E., Astrophysical Journal, xl. (December, 1014), pp. 435-442. 9 Jones' determination is in fair agreement with Kapteyn's final result, (Astrophysical Journal, xxx, p. 398):

[(photographic)-(visual)] losses= +0m0031 ± 0.0006.

The corresponding determinations by King (E. S.) of the coefficients of attenuation for photographic and visual light give values about five times that of the text.

10 The losses tom oo80 and tom co33 estimated by Jones for "photographic" and "visual" light lead to the values K1A=0'0073 and K2= o'0030 (wave-lengths not stated). Kapteyn's (corrected) estimate for wavelength 0431μ is K1A000507, leading to the value =0'68 × 105 hydrogen molecules per cm.3, which is of the same order of magnitude as the determination already made. E. S. King's results (footnote 1) increase the estimate of the text about five fold.

11 Note a discussion on this point by H. C. Plummer in a paper by H. H. Turner, loc. cit. (footnote 1).

found to exist between calculated and observed distributions of total starlight from different regions of the night sky. 12 The estimation of the amount of solar radiation scattered to the earth by a distribution of interstellar gas constitutes a definite problem, the complete statement of which (including the effect of self-illumination) is expressed as a particular case by a general integral equation already given by the writer. 13 The theoretical discussion applicable to the problem under discussion the writer hopes to undertake elsewhere; from the observational point of view it would seem that the difficult, but perhaps not impossible, task of estimating the luminosity of the sky in regions void of stars affords the only hope of bringing additional direct evidence to bear on some of the questions raised below.

14

In a gas of the extreme degree of tenuity which we have just estimated, molecular collisions will be extremely infrequent; an estimate of the free path, according to the usual ideas of the kinetic theory, is impossible without a knowledge of the average molecular velocity or temperature of the gas. As has already been pointed out by the writer, it is difficult to see how molecular velocities can be directly affected by radiation travelling through a gaseous medium. It is probable that gravitation and radiation-pressure are the controlling forces in determining molecular velocities by an extremely slow process of equipartition of energy with that of molecules escaping from planetary and stellar atmospheres.

As the above estimate of molecular density gives a total amount of matter of the order 1/38 x earth's mass in a sphere having a radius equal to that of Neptune's orbit, it is improbable that the residual gas we are considering could have a noticeable effect on planetary motions. It might, however, be identified with the slightly resisting medium the existence of which has been thought necessary by some astronomers to account for the secular acceleration of Encke's comet,15 and which is considered by See 1 to have played an important rôle in planetary and stellar evolution.

The molecular density estimated above is very much less than that conjectured to exist in some of the nebulæ, 10° molecules per cm.3 being about the order of magnitude in this case. 17 While the degree of rarefaction which we have derived is very much greater than it is possible to produce by any known physical means, 18 the total amount of matter contained in regions of space of astronomical dimensions is formidable; thus we find for the number of mole cules in a cubic parsec the estimate N=3·75 × 10°° hydrogen molecules per parsec3. Taking the density of hydrogen at standard temperature and pressure to be 0-0899 gramme per litre (containing 2-78 × 1022 molecules), we obtain for the density of matter in interstellar space the estimate 1-21 × 10 grammes per parsec3; as the sun's mass is approximately 1-96 × 10” grammes, we have finally for the density of interstellar residual gas the estimate 63 x 10" sun's mass per parsec3. According to Eddington,' a reasonable 12 Abbot, C. G., Astronomical Journal, xxvii. (1911), p. 20; "Annals of the Smithsonian Astrophysical Observatory," vol. iii. (1913), pp. 203-216 13 King, L. V., footnote (6), p. 379, equation (14).

14 King, L. V., footnote (7).

19

15 On the recent history of this comet see a paper by Backlund, Comet, 1805-1908," Monthly Notices, xx. (1910), pp. 429-442.

**Encke's

16 See, T. J. J.. "Researches on the Evolution of the Stellar System." 1910, vol. ii., pn. 134-158.

17 Henkel, F. W., in an article "Nébuleuses et Essaims," Scientia, vol. xv. (1914), pp. 294-307.

18 The total number of molecules per cm.3 corresponding to the vapourpressure of mercury at the temperature of liquid air is estimated at 3x107 (Dunoyer, M. L.. "Les Gaz ultra-raréfiés," in the collection "Les Idées Modernes sur la Constitution de la Matière," Paris, Gauthier-Villars, 1913, P. 216).

19 Eddington, A. S., "Stellar Movements and the Structure of the Universe.' Macmillan and Co., Ltd., 1914, p. 255.

estimate of the density of visible stars in the neighbourhood of the solar system is 10x sun's mass in a sphere of 5 parsecs radius (525 parsec3), i.e. 0·019 × sun's mass per parsec3. It follows that the density of "uncondensed" or "residual" matter existing in interstellar space is of the order 10s that of "condensed" stellar matter. Even if, as there is some reason to believe, the number of "dark" stars is very much greater than the number of bright ones (Lindemann's estimate is 4000),20 the ratio referred to is still very large.

It is evident that unless this "residual" or "primordial" gas is exempt from mutual gravitation it must give rise to a gravitational field very much greater than that of the whole sidereal universe, and should therefore be taken into account in existing theories of stellar dynamics. Although the dynamics of such a system would probably have to be modified to a considerable extent to take into account radiation pressure, we should still expect an enormously high density near its mass-centre, unless the whole be endowed with a small angular velocity, as is surmised to be the case with the Milky Way.

It follows from this brief discussion that we are either obliged to accept the existence of a widespread distribution of enormous quantities of interstellar gas of molecular density of the order 105 molecules per cm. and take into account its influence in stellar dynamics, or conclude that the attenuation of light by scattering is very much less than is indicated by existing estimates of the absorption of stellar radiation in space. LOUIS VESSOT KING.

McGill University, Montreal, June 30, 1915.

The Great Aurora of June 16, 1915. In reply to Dr. Chree's note in NATURE for July 22 - concerning the auroral display of June 16, I would say that the times (as indicated in my note in NATURE for July 15) were in Greenwich Mean Time. This, of course, begins at Greenwich Mean Noon. It did not occur to me that this might be misleading to the unastronomical reader. If one will subtract twelve hours from the times given by me, he will then have the dates for the morning of June 17 at Greenwich. Thus June 16d. 15h. 30m. G.M.T. will be June 170. 3h. 30m. a.m., Greenwich Civil Time.

I will take the opportunity to quote here from the Los Angeles (Cal.) Tribune of June 18, 1915, a despatch from Chicago dated June 17:

to-day

Soon, It was

Chicago telegraph operators were puzzled when their wires failed at times to work. however, the explanation of the trouble came. not due to power stations or lack of current, but to the aurora borealis.

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The bewildering beauty of the northern lights lighted up all of Canada and the north-western part of the United States last night and caused electrical disturbances that put telegraph wires entirely out of commission in Idaho, Montana, and the Dakotas and along the Canadian Pacific railroad.

"The disturbances extended to Chicago to-day and to-night, and reports of trouble between Pittsburgh and New York, St. Louis and Kansas City, and many other cities over the country, were received. Operators here stated to-night that the disturbance was the worst they had known in five years.

"W. F. Weber, wire chief for the Western Union, reported service considerably demoralised.

"Our wires the whole length of the land were badly affected early to-day,' he said. 'They are affected still, though not to such a degree. The disturbance of the atmosphere causes fluctuation of the 20 Lindemann, F. A., "Note on the Number of Dark Stars," Monthly Notices, xxv. (1915).

21 On this point note a remark by Eddington, loc. cit., p. 258.

current on the wires, and interferes with rapid transmission of signals. We have been obliged to operate at a much lower speed than normal to-day.' "The Postal Telegraph Company was similarly affected.

"It also was reported that train-dispatching on the Canadian Pacific railroad virtually ceased for several hours. Similar conditions prevailed on other northern transcontinental lines." E. E. BARNARD. Yerkes Observatory, Williams Bay, Wisconsin, August 4.

Use of Celluloid in Periscope Mirrors.

I SHOULD be glad to know, in reference to the possibilities of diminishing the danger in using periscopes under fire: (1) whether experiments have been tried as to the effect of cementing a plate of celluloid to the back of the exposed mirror in preventing or reducing the splintering of the glass when struck by a bullet, and, if so, with what result; (2) whether there is any danger involved in the use of celluloid for this purpose? EDWARD M. LANGLEY.

48 Waterloo Road, Bedford, August 17.

Foreign Philosophers.

ONE of the original objects of our Association for the Advancement of Science was to encourage the exchange of ideas with foreign philosophers, vide First Report of B.A. This year it will be a disappointment to many people in Manchester to have so few distinguished strangers. We now call them prisoners of war or alien enemies. But they still wish for scientific enlightenment.

Inquiries made in the prisoners' camp at Stobs reveal a small library_carefully catalogued. They have some hundreds of English books, including some scientific books; also, in German, Schiller and Goethe. They ask particularly for Naturwissenschaft in Deutsch, Chemie, Physik, Geologie, Botanik, also agriculture (Landwirthschaft), navigation, engineering, mathematics, mathematical astronomy for seamen, logarithms, Electrotechnik. There are repeated inquiries for a German book on spherical trigonometry, enough copies for the navigation class.

The requests we have the honour to transmit may be satisfied by sending books direct to Von Vorman, Librarian, Prisoner of War, Hut 18, Compound A, Stobs, near Hawick, Scotland. Inquiries as to books likely to be welcome in other camps may be addressed

to

the Emergency Committee, 169 St. Stephen's House, Westminster Bridge, S.W.

Some of the prisoners have already expressed a general willingness to remind their friends in Germany (with whom they are privileged to communicate) that the English prisoners in German camps are also asking for books.

Books sent by passenger train should be carriage paid, by parcels post they go free of charge. August, 1915. HUGH RICHARDSON.

French Magnanimity.

FRENCH history furnishes an interesting parallel to the magnanimity shown by Napoleon to the University of Pavia referred to in your issue of July 15. When Rudyerd was engaged in building the second Eddystone Lighthouse a French privateer captured some of his workmen and carried them prisoners to France. Louis XIV., however, as soon as he heard of it, put the captain and crew in prison, released the workmen, loaded them with presents, and sent them home, saying that though he was at war with England, he was not at war with mankind. GORDON D. Kлox. II, Garrick Street, W.C., August 17.

ANTARCTIC FOSSIL PLANTS.1

PROF. SEWARD'S Memoir is the first of the

British Museum Reports dealing with the natural history results of Capt. Scott's second Antarctic expedition. The work is finely illustrated, and provided with excellent maps. The specimens described are of unequalled interest among fossil plants, from their occurrence so near the Pole, and from the tragic circumstances of their discovery.

The report begins with a few notes on palæobotanical records from previous expeditions. Though of considerable interest as demonstrating the former existence of vegetation on the Antarctic Continent, these earlier records were of little

and less than six weeks before the end. The "beautifully traced leaves in layers" found in "veritable coal-seams" in the Beacon Sandstone, are found to belong to the well-known species Glossopteris indica, which is thus shown to occur in abundance only about 300 miles from the South Pole. The fact that there is some evidence of drifting does not materially affect the interest of this astonishing discovery. The nature of the plant is beyond doubt, as shown by the excellent photographs, and the finding of so well-characterised a member of the Gondwana Flora was peculiarly fortunate. The stems and scale-leaves of Glossopteris also appear to be present.

The fossil wood, Antarcticoxylon priestleyi, from the Priestley Glacier, is described in full de

tail, with the aid of numerous microphotographs; an interesting point is the presence of well marked annual rings. The occurrence of concentric bands of cellular tissue in the wood is a peculiar feature, possibly to be explained as a reaction to wounding during life. The wood shows affinity with that of Cordaites, but is regarded as the type of a new genus.

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The author might perhaps have compared his specimens with Mesopitys tchihatcheffi, a Permian plant from the Altai, fully described by Zalessky in 1911; the two stems have a good deal in common, notably in the presence of annual rings, the single leaf-traces and the structure of the primary wood.

FIG. 1.-The medial moraine on the Priestley Glacier. From "Antarctic Fossil Plant," by A. C. Seward, F. R.S.

botanical value, none of the specimens admitting definite determination. The really important Antarctic specimens of fossil plants are among the fruits of Capt. Scott's second expedition.

The petrified remains of a tree, named by the author Antarcticoxylon priestleyi, were discovered by the northern party on February 1, 1912, on the moraine of the Priestley Glacier, south of latitude 74° S. Still more important discoveries were made by the Polar party at Mount Buckley in latitude 85° S., on February 8, 1912 (see our illustration). This was on their sad return journey

1 "Antarctic Fossil Plants." By A. C. Seward, F. R.S. British Museum (Natural History). British Antarctic (Terra Nova) Expedition, 1910. Natural History Report. Geology, vol. i., No. 1, pp. 1-49+ viii plates. (London, 1914.) Price 6s.

Other, less well preserved, specimens of Antarctic wood are all regarded as probably Gymnospermous.

A curious discovery is that of a body (Pityosporites antarcticus) apparently representing a winged pollen-grain; it was found in the matrix of a partially decayed stem of Antarcticoxylon. Winged pollen-grains occur both in the Firs and the Podocarpineæ; on geographical grounds the | latter group appears the more probable, but the I agreement with the pollen of the Abietineæ seems I to be closer.

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