and replaced the Turks just named, taking possession of their settlements and capital, and continuing their culture. They also adopted the new name of Uighurs, which the Chinese, having, as I have said, no letter "r," changed into Hoei Hoei and other distorted forms of the name Uighur.

THE LIVING PLANT.

Botany of the Living Plant. By Prof. F. O. Bower. Pp. x+580. (London: Macmillan and Co., Ltd., 1919.) Price 255. net.

A GOOD deal of discussion has recently taken

These Uighurs became a highly cultivated people, with a considerable literature, which is still extant, and their dialect is known as Eastern Turki. They apparently inherited from the Western Turks an attachment for the Iranian or Zoroastrian religion, and traces of the Zoroastrian gods and ritual are found among their remains. On other sides their religion was affected by missionaries from other sources. Manicheism found numerous recruits among them, and we are now fast recovering from the buried cities of Eastern Turkestan most interesting remains of the religion of Manes, while the Nestorian clergy founded episcopal sees in their country, and made numerous recruits. Presently, and in the seventh century, Buddhism also made its way among them in the corrupt form, and mixed with the Tantra superstitions, which then prevailed in Tibet, and is known as Red Lamaism in contrast with the reformed Lamaism of the later Yellow Lamas.

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place among botanists on the subject of the reconstruction of elementary botanicalory teaching, and one of the main contentions of the originators of the discussion was that in order to secure improvement "comparative top morphology should be reduced to a subordinate position. It has further been alleged that in modern botanical teaching the teacher has failed to present the plant as a living organism, thereby implying that morphology has been divorced from physiology. Prof. F. O. Bower has already pira expressed himself forcibly and with sound sense upon the question in the pages of the New Phytologist (vol. xvii., Nos. 5 and 6, p. 105), pte and has aptly summarised his views with the adage, "Physician, heal thyself."

At length, in the ninth century, the religion of Islam found its way into Central Asia, being disseminated from the Central Asiatic State governed by the Samanis, and the Western Turks became eager converts to it both in the frontier steppes of the Persian Empire and in Eastern Turkestan. The Eastern Turks or Uighurs continued to be the more cultivated of the race, but the Western were the more powerful warriors, and under the name of Turcomans overran Persia and Asia Minor, founding the famous empire of the Seljuki, which was presently (in the thirteenth century) overwhelmed by the Mongols.

In his book now under notice he has given so admirable a presentment of the plant as a living organism that instead of there being any antagonism between physiology and morphology, their fusion and interdependence are so impressed on the reader that he can see, not two entities, but one flesh.

Prof. Bower concludes the article to which reference has been made with the following: 'Finally, each teacher with a due sense of his responsibility, and of his opportunities and requirements, must form his own scheme to meet his own needs. If he cannot do this he is not fit for his position."

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Prof. Bower has followed this very pertinentes a criticism with his book, "The Botany of the Living Plant," which is framed on the lines of the annual course of elementary lectures on botany given by him at Glasgow for more than thirty years. main object has been to present the plant as a living, growing, self-nourishing, self-adapting s creature, and he has very finely achieved his ideal. In his method of treatment of the subject he has allowed the living plant to tell its own story, slowly and naturally unfolding itself stage by stage in such a manner that interest is aroused and observation stimulated. The book may very justly be regarded as an invaluable contribution to sound learning. It does not aim at being an exhaustive treatise, but deals with the fundamental facts of plant life, and is written in a remarkably clear style, so much so that anyone with only a slight acquaintance with plant life should be able to acquire a real knowledge of the science of botany from a careful study of these describ

I am conscious of the extremely meagre and arid nature of this epitome, and how little it does justice to the wide reading and sound judgment of the author. No one knows it better, for I have spent a large part of my life in writing four fat volumes on the Mongols, and two sets of papers on the westerly drifting of Nomads and the northern frontagers of China in the old Ethnological Society's Journal and the Asiatic Journal respectively. This may give me at least a claim to speak in terms of high praise of the work before me, in which the author, having the unusual advantage of knowing Russian, has employed it with generous profusion, much to our profit, and in which she describes with clearness the various divisions into which the Turks have been disintegrated, with their geographical, ethnographical, and religious features, and also tells the story of their doings. It is so well done that I cannot pay the book a greater compliment than to repeat my invitation to the learned lady who has written it to give us a much larger work on the subject. I may add that a most ample bibliography occupies. 114 of the 242 pages comprised in the work. HENRY H. HOWORTH.

NO. 2611, VOL. 104]

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The opening chapter is occupied by a careful and comprehensive description of the seed and its germination. It is sometimes considered more reasonable to commence the study of botany with the lower forms of plant life, but it is obviously a better plan to set out with a familiar and easily handled object, such as the seed, which marks a

definite starting-point, and can be examined and studied in detail without recourse to the microscope. It is pointed out that in the plan of construction of the higher plants the outstanding feature is the capacity for indefinite vegetative increase which may be termed "continued embryology."

The cellular construction of the plant and the various functions of the cell, cell-division, and protoplasmic continuity naturally follow, and then the tissues are dealt with in further detail. The sequence of events next leads to an account of leaf and root from the morphological point of view, followed by chapters on the relation of plants to water, and on nutrition, storage, and respiration. In the chapter on growth and movement due attention is paid to the statolith theory in connection with geotropism. Succeeding

chapters deal fully with the mechanical construction of the plant body, modifications of form in the vegetative system, such as bulbs, tubers, climbing plants, etc., the irregular nutrition of parasitic, semi-parasitic, and carnivorous plants, and vegetative propagation, all of which aspects of plant life are fully discussed with a wealth of well-chosen examples.

The inflorescence and flower and the formation and development of the seed with all that is entailed occupy some eighty pages and bring this first division of the book to its logical conclusion. This portion is not a mere chron.cle of wellknown facts, but is illuminated by a consideration of flower colours, pollination, and the details of fertilisation, and closes with a description of the mode of dispersal of some of the better-known seeds and fruits.

The second part of the book is arranged in four divisions, dealing respectively with the Gymnosperms, Pteridophyta, Bryophyta, and Thallophyta, followed by two chapters, one on sex and heredity, the other on the alternation of generations and the land habit. These two essays very fittingly come at the end as a summary of the previous chapters dealing with the life-histories of the lower plants.

As in the earlier part of the book, these more specialised chapters on the ferns, mosses, fungi, and algæ are treated on broad lines, and there is no superfluity of detail to obscure the salient features.

The book concludes with two appendices, one on the types of floral construction in Angiosperms, the other on vegetable foodstuffs, both of which considerably enhance the value of the volume. In the former a few types of flower are described, and notes are added on the natural families to which the particular examples belong. The plants chosen are easily accessible and also represent characteristic features of families the products of which are of economic importance. Further, they are of interest in connection with the production and dispersal of seeds, floral biology, etc. The illustrations in this appendix have been drawn for the most part by Dr. J. M. Thompson, and are particularly clear and useful.

The glossary-index, which completes the book, occupies thirty-two pages, and furnishes a further example of the thorough and careful manner in which Prof. Bower has carried out his object.

We have for so long been accustomed to rely on translations of German text-books for our elementary botanical students that it is very gratifying to find them superseded by so excellent and comprehensive a study of the living plant from one of the most eminent of our own professors and teachers. A. W. H.

OUR BOOKSHELF.

Influenza: A Discussion opened by Sir Arthur Newsholme. Pp. 102. (London: Longmans, Green, and Co., n.d.) Price 3s. 6d. net. THE discussion on influenza at the Royal Society of Medicine in November last summarises very completely our knowledge of this obscure epidemic disease. Sir Arthur Newsholme, in his opening remarks, expressed the opinion that influenza is a specific disease recognisable in severe outbreaks, and pointed out that, with the exception of plague and cholera, it has on occasion travelled farther and more rapidly over the world than any other recognised disease, and that it is one over which preventive medicine so far has secured little or no control.

Dr. Stevenson directed attention to certain features of the 1918 epidemic which differed from those of the past twenty-seven years, viz. (1) its intensity was greatly in excess of that of any of its predecessors, and (2) the sudden and startling change which occurred in 1918 in the age distribution of influenzal mortality. In all previous years the majority of deaths-generally about 70 per cent. occurred at ages above forty-five. But in July, 1918, only about 30, and in October about 20, per cent. of the persons dying were more than forty-five years of age, and only 5.5 per cent. of the deaths of this outbreak were at ages above sixty-five, as against an average of 37 per cent. for the years 1890-1917.

Several speakers dealt with the aspects of the epidemic in the Navy and in the Army, and in France, America, and South Africa, which correspond closely with those observed among the civil population here.

With regard to the bacteriology of the disease, most of the observers noted the presence of the influenza bacillus, the pneumococcus and the streptococcus, but no very definite opinion is expressed as to the nature of the virus. Prophylactic vaccination receives scant notice, probably because the data were insufficient at the time of the meeting.

As regards treatment, Mr. E. E. B. Turner claimed that large doses of salicin constitute a specific, and certainly his experience, based on the observation of 2500 cases, suggests that this drug deserves an extended trial.

R. T. HEWLETT.

The "Daily Telegraph" Victory Atlas of the World. Part i. (London: "Geographia," Ltd., 1919.) Price is. 3d. net.

THIS is the first part of a new atlas to be completed in about forty-eight parts. Each part is to consist of three double-page maps, 20 in. by 26 in. A gazetteer is to complete the work. The first part contains maps of Australia (physical), South-West Spain (political), and Germany (historical), besides several inset maps. The colour printing is good and the lettering particularly legible. The orographical map of Australia is layer coloured, and although it shows some small discrepancies from the recently published official orographical map of the Commonwealth it is an effective and useful sheet. The map of Spain, which we take to be the type of political map of the atlas, would be improved by the omission of the "caterpillar " relief, which is merely misleading and of no value. In this respect the map of Germany is better, for no attempt is made to show relief on it. The changes due to the Peace Treaty are incorporated, but a mistake is made in the area of the Slesvig plebiscite. The atlas promises to be a useful one for general reference purposes. Its low price is much in its favour. R. N. R. B.

The Mica Miner's and Prospector's Guide. By Archibald A. C. Dickson. Pp. viii+50. (London: E. and F. N. Spon, Ltd., 1919.) Price 4s. 6d. net.

THE mica industry is indebted to the author of this "Guide" for the current system of mining in Kodarma, the most prolific mica field in the world. His memoirs on that field are well known. Any contribution of his to the literature of the .subject is therefore sure of careful consideration. The present booklet, which is high-priced-fifty pages for 4s. 6d.—was prepared to help the increased output of mica necessary during the war. It contains much valuable information, but does not cover all the ground that might be expected from the title. It consists mainly of descriptions of eight of the secondary mines of the Kodarma field and of notes on the mining methods there. It contains little information as to costs and values, and would not explain to a miner who had no previous experience of mica-mining how to estimate the probable profit or loss of a newly discovered deposit. The author's main thesis is that mica-mining must be guided by careful geological study, and he insists that all the facts observable during the working of a deposit should be systematically entered on a mine plan. This warning is especially useful with a branch of mining in which so much of the output is from small mines worked by parties of local labourers. Mr. Dickson points out that the mica lenses on the margin of a deposit are apt to be inclined to the shoot, and a miner who was guided only by the facts seen would be diverted from the main body of mica.

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.]

Scattering of Light by Resonating Molecules. PROF. R. W. WOOD (Phil. Mag., vol. xxiii., p. 689, 1912) found that mercury vapour, even at the small density corresponding to atmospheric temperature, when illuminated by the ultra-violet mercury radiation A 2536, re-emits this radiation laterally in considerable intensity.

. Further, Wood and Kimura found after repeated examination that this radiation is completely free from polarisation (Phil. Mag., vol. xxxii., p. 329, 1916).

I have been very much impressed with the contrast between this case, where there is resonance, and the behaviour of gases in general when illuminated by light which is not in resonance with the free period of the atoms. In the latter case the laterally emitted light usually approximates to complete polarisation (Proc. Roy. Soc., A, vol. xcv., p. 155, 1918). What happens as we gradually depart from exact resonance?

Prof. Wood's experiments were made with the exciting light polarised, and he observed the resonance radiation through the same window by which the exciting light entered. In this way the light examined comes chiefly from the very first stratum of vapour entered by the beam. This stratum gives by far the most intense emission.

As, however, the beam advances into the mercury vapour the light in exact resonance is absorbed, being, in part at least, re-emitted. The lateral emission further on is much fainter, and corresponds presumably to a less exact resonance.

It appeared to be of interest to examine this lateral emission from the deeper strata for polarisation. This I have done, and I give here a brief statement of results, leaving the experimental details for later publication.

After the unpolarised primary beam has traversed 94 cm. of mercury vapour at ordinary temperature, the lateral emission shows very perceptible polarisation, the component intensity vibrating parallel to the exciting beam having 90 per cent. of the intensity of the perpendicular component.

After passing through 2.5 cm., this ratio fell to 82 per cent.

The

After 274 cm., the value found was 60 per cent. Thus it appears that the scattered light is unpolarised only when resonance is very exact. breadth of the absorption band (reversal) produced by a few millimetres of mercury at atmospheric temperature and in vacuo must be extremely small, and probably beyond the range of any but the most powerful spectroscopes. Yet it is only within this narrow spectral range of the exciting light that the scattered light is sensibly unpolarised. When this component is filtered out, and such excitation as remains is by light nearer the edges of the exciting line, polarisation becomes conspicuous.

It need scarcely be said that there is very much more to be done in this direction. Further experiments are in progress. RAYLEIGH.

Imperial College, South Kensington,
November 1.

mentier, for irrigating orchards and market-gardens in Syria, Palestine, and other countries subject to long summer droughts. The observations of M. Parmentier refer especially to the citrus gardens around Jaffa. In arid climates economy in irrigation-water is obviously of the utmost importance. According to the method proposed by M. Parmentier, the water is applied direct to the roots of each tree by means of earthenware, cement, or iron pipes fixed vertically in the soil. The great losses by evaporation that always occur in open canals and in surface irrigation are thus avoided.. M. Parmentier remarks that with vertical-pipe irrigation the water used in a citrus orchard was only 84 litres per hectare, as compared with 600 litres necessary for surface irrigation, applied every five to twelve days. At Jaffa there are 880 trees to hectare (2 acres) of citrus orchard, and 1100 plants in the banana gardens. These figures are very high, and imply a great consumption of water.

The method proposed by M. Parmentier is not new. Watering orchards by means of special drain-tubes sunk vertically in the soil is an old practice at Messina, in Sicily, where it is chiefly applied to young plantations. This method of irrigation was first described long ago by Prof. Giuseppe Inzenga, the well-known Sicilian agronomist and botanist, in the Annali di Agricultura Siciliana; and again by F. Alfonso-Spagna in his "Trattato d'Irrigazione (Palermo, 1877, p. 502). In my book of agricultural chemistry ("Chimica Agraria, Campestre e Silvana," Napoli, 1902) this special method of drainage-irrigation is again described. The catuso used by the Messina gardeners is a conical earthenware pipe, about 1 metre long, open at both ends. The diameter of the upper opening is 15 cm. and that of the lower 10 cm., the pipe thus holding about 12 litres of water. M. Parmentier proposes pipes holding 20 litres for use in orchard irrigation. At Messina the upper end of the catuso projects slightly above the soil, the opening being covered with a brick or tile.

In the summer of 1889, at Portici, near Naples, I experimented on two lemon-trees of the same age and size, watering one in the usual manner and the other by means of a drain-pipe sunk vertically in the earth. During that hot summer, in the sandy, volcanic soil at the foot of Vesuvius, the difference between the effects of the two methods of watering was very apparent. The lemon-tree provided with the vertical drainage-pipe prospered on a ration of water about 50 per cent. less than that necessary for the control tree watered from the surface.

The sunk end of the drainage-pipe is made to rest on loose stones or potsherds, which form air-chambers. Thus clogging of the pipe is prevented, and the water that is poured down gets well absorbed and distributed just where the roots are more vigorously developing and renovating their absorbing organs.

The subsoil air-chamber is as important as the water-pipe. During drought the deep aeration of the soil, when moisture is sufficient, provokes the growth of the roots and the renewing of the root-hairs, increasing their power of absorption and at the same time favouring deep-soil nitrification. The roots are induced to develop chiefly around the reservoir of moist, warm air, where respiration and growth find favourable conditions, the network of young and active rootlets thickening around the spot where the watering is concentrated and nitrates are being actively formed. The loss by evaporation and percolation is minimised. Moreover, the close air under the foliage of the trees, as M. Parmentier remarks, is maintained in a less damp condition than is usual in the deeply shaded citrus orchards, where the

development of parasites and pests is much favoured by the moist shade.

M. Parmentier observed that vegetables watered by underground irrigation are more tender and of higher market value than vegetables watered by submersion, or by any other method by which the foliage, stalks, and upper parts of the roots are wetted. Indeed, it may be added that the wetting of the foliage increases transpiration, and consequently the waste of water.

By means of vertical-pipe irrigation dilute liquid manure can be applied far more effectually and economically than by the usual method of night-soil manuring In the case of vegetables and fruit-trees subsoil liquid manuring is also advisable from a sanitary point of view.

In arid climates, and wherever the economy both of water and of liquid nitrogenous manure is of special consequence, the Messina and Parmentier method of underground watering by vertical drainage is much to be recommended. ITALO GIGLIOLI. Laboratory of Agricultural Chemistry, University of Pisa, Italy.

New Sources of Aluminium.

I WAS much interested in the account given in NATURE of October 23 of the new methods of extraction of aluminium from clays of the kaolin class (formed from the denudation of volcanic rocks) by means of nitric acid and electric furnaces in Norway. When this source of production is generally adopted, as no doubt it will be owing to the diminishing supplies of cryolite and bauxite, it seems probable that the vast quantities of "decomposed porphyry" discovered by the late Prof. Jacob during his geological explorations in the Rocky Mountains (some of which have been mistaken for chalk by prospectors) will then form an inexhaustible source of supply for that valuable metal. J. E. BACON.

The Barracks, Fulford, York.

Radiation Temperature: Dew. THE letter in NATURE of October 23 on radiation temperature from Mr. Spencer Pickering reminds me that the theory of the equilibrium temperature is given by Clerk Maxwell in his little-known article on Diffusion ("Ency. Brit.," ninth edition, p. 218). Maxwell shows that in still-air temperature 0, a thermometer will gain heat per sec. 47ČK(0,-0,), where C is the electrical capacity of the bulb, K the conductivity constant for air; and that it will give up heat per sec. AR(0,-0), where A is the area of the bulb, R the radiation constant, and the temperature towards which radiation occurs. If the bulb be spherical C=r, its radius. Consequently,

or

4rK(0-0)=4πr2R(0,-0),

K(0,-9)=rR(0,-0).

That is, the conductivity effect depends on the radius of the bulb. Mr. Pickering has observed this in the case of small bulbs. He goes on to apply this result to small objects, such as the pistils and stamens of flowers. I would like to point out another effect to which his observations apply, namely, that true dew (arising from radiation) is not found on spiders' webs. If webs are examined when dew is on the ground they are found to be dry. When drops of water are found they arise from the collecting action of the webs on mist or fog, i.e. by the collection of drops already formed. I have confirmed this on many occasions. I conclude that whenever drops are found on webs it is the result of fog or mist.

SIDNEY SKINNER. South-Western Polytechnic Institute, Chelsea.

Surface-Tension.

OWING to surface-tension, a surface of mercury supports easily a sovereign placed flat upon it. Care must, of course, be taken to avoid amalgamation.

I shall be greatly obliged if one of your readers will supply me with a formula for determining the size of the largest sphere of gold that can just be supported by mercury. As the numerical solution of the equation may be troublesome, I venture to ask only for the formula. C. T. WHITMELL.

Hyde Park, Leeds, November 3.

Exceptional Dryness of October, 1919. METEOROLOGISTS have directed attention to the It is also exceptional dryness of the past October. interesting to note that the amount of drainage-water percolating through 20 in., 40 in., and 60 in. of soil in the open field for the month of October as recorded by the Rothamsted Experimental Station gauges is nil. The three gauges, each measuring 1/1000 acre, were built in 1870, and in no previous year is October shown quite dry, 1897 being the nearest with a reading of 0-001 in. The following are the figures for October :—

40 in. gauge

60 in.

I-798

...

5.589

6.764

nil

o 960

observation stations are marked. This is the essential idea underlying sound ranging. Three stations only are necessary, but more may be employed in order to confirm the location.

There are other ways of plotting the gun position, given the time intervals. For instance, if the time interval between A and B is t1, the gun must lie on a hyperbola with foci at A and B which is such that the difference in the distances from the foci of any point on the curve is Vt, where V is the velocity of sound. Another pair of stations give another hyperbola, and by finding where this intersects the first the gun position is determined. This was the method actually employed on the plotting-boards used by the soundranging sections. The hyperbola approximates so closely to its asymptote near the gun position that the asymptote can be used equally well, which makes the method a very simple one in practice.

The French Army started experiments in sound

S

Max. 1891

W. D. CHRISTMAS.

The 50-year records show that October is one of the four months when the ground is wettest.

Lawes Agricultural Trust, Rothamsted
Experimental Station, Harpenden,
November 6.

ranging in 1914, and obtained results which showed that the method was a promising one. From the very beginning development took place along two lines. Either observers were used, who recorded the time of arrival of the sound by pressing a key, or the sound was registered automatically by some form of microphone. In both cases the stations were connected electrically to a central station, where the signals sent by the observers or microphones were registered on a chronograph of some form. It was soon found that observers were not sufficiently accurate. They made errors amounting to one-tenth of a second, whereas it is necessary to time the arrival of a sound to 0.005 second in order to make a satisfactory location. This accuracy was attained by the system in which the arrival of the sound was registered by a microphone, and both in the French Army and ours a microphone system was finally adopted.

Suppose that there is a gun at the point S in Fig. 1. The report of the gun spreads as a spherical sound-wave, with a uniform velocity, and is received by stations at A, B, and C. If the time intervals between the arrival of the sound at A, B, and C are measured, a very simple construction gives the position of the gun. For instance, if the sound gets to B a time t1 after it gets to A, and to C a time t2 after it gets to A, circles are described around B and C the radii of which are equal to the distances travelled by sound in times t, and t2 respectively. If a circle is found which passes through A, and touches the circles around B and C, the gun position will be at its centre. Therefore, by installing a series of observation stations along the front at surveyed positions, and recording the times at which the report arrives at these stations, it is possible to plot the position of the enemy battery on a map on which the NO. 2611, VOL. 104]