aerobic and anaerobic decompositions proved entirely too much for the author :

"Curiously enough, he says, "some scientists say that if air is admitted to the soil nitrogen is set free from the organic matter; and, on the other hand, if air is excluded, nitrogen is set free from the nitrates; and in both cases it is lost. These views would appear to be mutually destructive."

The chemist is still worse: when appealed to by growers to help in checking plant-diseases, "the chemist, like a sensible man of business, immediately proceeded to compound his nostrums and to talk learnedly about the fungoid and other diseases, at the same time not forgetting to take the fees to recompense him for his learning and skill."

But perhaps the most severe treatment is reserved for Rothamsted.

"The cultivation seems to be of the poorest description; in fact, it can hardly be described as cultivation at all. . . . One can imagine the condition of the soil . . . it must be almost as hard as rock, and impervious to rain, air, or roots. Farming on the Rothamsted principle would appear to be a very precarious business."

As all this occurs in a science section, first-hand information was apparently deemed superfluous; nevertheless, a visit to Rothamsted first of all might not have been a bad idea. After this we are quite prepared for the author's scheme for making the wheat crop yield a profit of more than 70l. per acre, instead of 41. or less as at present. The experimental basis consists of a trial made at Ealing in 1910 with 400 seeds; the results are multiplied up till they can be expressed in terms of one acre; and this in turn is multiplied up till the author foresees that "thousands of men would be kept on the land at better wages, and our wheat crops would be increased enormously. Agriculturists would do well to consider the above figures before smiling too broadly at them.' Unfortunately, agriculturists have had these paper schemes presented to them fairly often for at least 250 years past, and now they require facts. Enough has been said, however, to show the sort of "science" that is considered good enough for growers. E. J. RUSSELl.

TEXT-BOOKS OF PHYSICS. (1) Experimental Mechanics and Physics. By A. H. E. Norris. Pp. viii+176. (London: Mills and Boon, Ltd., n.d.) Price 1s. 6d. (2) Elementary Physical Optics. By W. E. Cross. Pp. 312. (Oxford: Clarendon Press, 1913.) Price 3s. 6d.

Students. By J. A. Randall. Pp. xiv + 331. (New York: John Wiley and Sons; London : Chapman and Hall, Ltd., 1913.) Price 6s. 6d.

net.

(4) 4 Synopsis of the Elementary Theory of Heat A and Heat Engines. By J. Case. Pp. iii+65. (Cambridge: W. Heffer and Sons, Ltd., 1913.) Price 2s. 6d. net.

(5) Elementary Principles of Electricity and Magnetism for Students in Engineering. By Dr. R. H. Hough and Dr. W. M. Boehm. Pp. vii+233. (New York: The Macmillan Company; London: Macmillan and Co., Ltd., 1913.) Price 65.

(6) Transport de Force. Calculs Techniques et Economiques des Lignes de Transport et de Distribution d'Energie Electrique. By C. Le Roy. Deuxième Partie. Partie. Pp. 143. (Paris: A Hermann et Fils, 1913.) Price 6 francs. (7) First Year Course in General Science: A Combined Text-book and Note-book. By E. A. Gardiner. Pp. vi+113. (London: W. Heinemann, n.d.) Price 2s. 6d. net.

HE title of this little book is rather mis

(1) Tleading. The use of the word "physics"

suggests that the contents of the book comprise the various branches of physics, and not merelyas is actually the case-heat and a meagre treatment of a few of the properties of matter. These subjects occupy only one quarter of the volume, the remainder being devoted to mechanics. The treatment is very simple and is suitable as an introductory course. In this respect the book will no doubt serve its purpose as efficiently as many others of its class, although it exhibits no noteworthy advances in the mode of presentation of the subject. The frequent change of type is rather an unfortunate feature, and some of the diagrams are very badly drawn, notably a cube used to represent the measurement of volume, the perspective of which is in exactly the wrong sense.

(2) This book has several very good points. The subject is treated in a straightforward and lucid manner. The author has endeavoured to develop the theory of optics upon both "ray " and "wave" bases simultaneously, and we think he has succeeded. There is much to be said for both methods of treatment, and neither should be ignored. As is natural in an elementary treatise, no very difficult problems are considered, but it is rather surprising to find practically no reference to diffraction and interference, especially as some stress is laid on the wave theory. many simple experiments in this connection which, far from confusing a junior student, would undoubtedly interest him. One of the most notable

There are

features of the book is the series of diagrams, which are well drawn, and often a whole page is devoted to a single figure, with the result that a very clear representation is secured.

(3) One is inclined to think that too much is being done nowadays in the matter of adapting branches of study to the special needs of various classes of students. Text-books of physics, and presumably of other subjects also, are written from the point of view of subsequent work, and the result is often detrimental to the students themselves. It is scarcely possible to avoid a certain looseness of language and an inexactness of expression when the subject is submitted to the special mode of treatment in question. The present book is quite a good one in many ways, and no doubt contains a great deal of useful information with regard to heat and heat engines. It is good to find the subject introduced from the point of view of energy, although the discussion of the meaning of energy is evidently handicapped by the knowledge on the part of the author of the very limited training in mechanics possessed by the students for whom the book is written. To each chapter the author appends a summary in heavy type of the important conclusions therein, together with a number of problems based on the work. Apart from the limitations imposed by the mode of treatment referred to, this book is a straightforward and lucid presentation of the subject.

memory,

(4) This pamphlet is frankly published for "cramming" purposes. It is intended as a synopsis for students reading for the Mechanical Sciences Tripos, and especially for the "A" paper in Heat. In order to make this perfectly plain the author leads off with some forty lines of doggerel, which, if committed to apparently ensures success in the examination. To those students who regard their study of physics from this point of view, the book will prove useful in proportion to what they remember of its contents; to the serious student it can scarcely be recommended. For so small a volume the table of "errata" is too long; indeed, it rather looks as though this handbook has been hurriedly prepared.

(5) There is room for doubt as to whether it is desirable in a book on electricity and magnetism to avoid almost entirely references to the physical, as distinct from the mathematical, side of the subject. This is the only fault we have to find with this treatise, which is otherwise quite excellent. And even this objection disappears if it can be guaranteed that the book will be read concurrently with attendance at experimental lectures and laboratory work. Most teachers find

that students of physics experience much me difficulty with the mathematics it involves thr with the experimental principles upon which r based. To those students this book should pro a boon. Here they will find presented in lega order and in a simple manner an extensive serx of deductions from, and applications of, the fundmental laws of electrostatics, magnetism, arelectromagnetics. Numerous numerical examp are appended to the various chapters, and at the end of the book the more important formulæ veloped in it are compiled in a list. The use of this list, of course, involves the adoption of a par ticular notation in the memory of the student, au this, perhaps, is a little inexpedient at a time li the present, when notation varies so much; but is not easy to see how to overcome the difficulty

(6) To those interested, both theoretically and practically, in the transmission of electrical powe this volume should prove of great interest and use. The author has carried out a large numes of calculations of the various electrical data re quired in this connection, with numerical examples Graphical methods are frequently resorted to, and the treatment of the whole subject appears to b very complete.

(7) The chief objection to this type of book that it is very liable to become very dirty a the hands of a slovenly boy, and very unsight, owing to numerous corrections, when written up by a boy who, though clean, is not brilliant. The instructions for the experiments are given clear's and neatly, and it seems rather a pity to spal their appearance. The course comprises th parts, arranged more or less in order of difficult. and a considerable number of simple experiments in mechanics, heat, and the physical and chem properties of water and air are dealt with. the end of each lesson a number of questions, intended for homework, are set. Presumably the answers to these are to be recorded in a separate notebook. Why not the experimental results also?

OUR BOOKSHELF. Vegetation of the Peak District. By Dr. C. E Moss. Pp. x+235 + plates. (Cambridge University Press, 1913.) Price 12s. net. QUICKLY following on Elgee's "Eastern Molands of Yorkshire," we have Moss's book on the vegetation of the Peak district, especially in s relations to geology and the chemical nature of Elgee, are not considered by Moss. the soil. Faunistic relations, so ably discussed by As the auth remarks, the Peak district has no definite geographical boundaries, but his maps of the plant formations include the area lying between Mossley and Penistone to the north, and, approximately

Congleton and Matlock to the south, embracing portions of five counties, and sources of several head-streams of the Mersey, Dee, Trent, and Yorkshire Ouse.

There are several elevations of a little more than 2000 feet, and a large proportion of the district consists of unenclosed moorland and grassland. The maps are coloured to show the plant formations of acidic peat, siliceous soil, calcareous soil, sandy soil, and of cultivated land. The plant formations are subdivided into associations. For example, the formation of acidic peat exhibits associations in which Vaccinium Myrtillus, Eriophorum vaginatum, Calluna vulgaris respectively dominate, and others in which two of these units are more or less equally dominant.

Following an introduction, dealing, among other things, with rainfall, temperature, and winds, are chapters on woodland, scrub, grassland, moorland, rocks and screes, marsh, and aquatic and cultivated land associations. Summaries of the plant communities (these include formations and associations) of the Peak district and of Britain conclude a most interesting book, the illustrations and maps of which are excellent. W. B. H.

Outlines of Stationery Testing. A Practical Manual. By H. A. Bromley. Pp. 74. (London: C. Griffin and Co., Ltd., 1913.)

Price 2s. 6d. net.

THIS little manual deals chiefly with the technical examination of paper, though other articles of stationery are included in its scope. It avoids theoretical considerations, and gives in simple language concise instructions for the practical testing of paper, physically, microscopically, and hemically. Under the first heading come questions of colour, nature of the paper, surface or "finish," texture, opacity, ink-bearing properties, and strength. Short notes are supplied explaining these terms as applied to paper, and the methods of testing the properties indicated by them.

Few words are wasted in the chapter devoted to explaining the microscopic examination of paper. The author has managed to condense the description of the examination into five small pages, whilst another five are allotted to plates showing the microscopic characters of the principal fibres. Under the head of chemical examination, directions are given for determining the nature and mount of the mineral matter used as "loading," and of the organic substances, such as gelatine, rosin, casein, and starch, employed in the "sizing" of paper. Methods are also propounded for discriminating the colouring ingredients and detecting chemically certain fibres and impurities. In all cases, the author claims, the chemical processes described are those which require the simplest possible apparatus. The characteristics of special kinds of paper are indicated briefly, and the book concludes with short sections on the testing of ink, gum, sealing-wax, and other miscellaneous articles included in the "stationery." Within its limits-those of a col'ection of notes for use in practically examining Stationery-the book will be found useful.

term

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.]

Pianoforte Touch.

I CAN fully endorse Dr. Heaviside's opinions as to the possibilities of the piano-player, and could only wish that there were some reasonable prospect of this instrument being used to save a great portion of the uninteresting drudgery of the usual school musiclesson. At the present time a considerable amount of school time is wasted in attempting to learn an instrument which is so difficult to play that few succeed in obtaining any satisfactory results. This system does not succeed in producing musicians any better than the ordinary school algebra lesson succeeds in producing mathematicians.

On the other hand, my recent experiments in connection with this "patent" control have led me carefully to test the existing commercial piano-players, and I can fully endorse Mr. Wheatley's complaints as to their lack of responsiveness and their persistent assertion of their mechanical individuality in opposition to the most strenuous efforts of the performer controlling them. The methods of varying expression by means of punch-holes, or by damping down all the notes on one side or other of a hard and fast

dividing line, produce a very pleasing impression at first, but one soon tires of their very limited capabilities.

In these circumstances I would strongly recommend Mr. Wheatley and any other readers of NATURE who are interested in the subject to experiment with the methods of control claimed in my patent specifications. Even a rough and ready device rigged up with sticks, strings, and kitchen weights produces such a great improvement in the range of effects and flexibility of the instrument that after experimenting with such an arrangement I found it impossible to obtain any satisfaction without it. I think it may be safely said that the mechanical self-assertiveness of the instrument can be reduced to a small quantity of the second order, and can be further reduced by a method of successive approximation. So soon as dynamical considerations are introduced the possibility of accenting notes in chords (i.e. proper chords, not the miserable arpeggios which are so often substituted for them in recently cut music rolls) becomes evident, and the production of variations of tone quality by differences of touch is probably much easier when effected this way than when the keys are played by hand. All this appears less difficult to learn than the control of the speed regulator, which must always remain a difficulty.

The absence of these capabilities constitutes the great defect of the commercial player. But the ordinary "practical man" cannot understand anything based on the principles of dynamics and physics, consequently he treats the pressure as if it were constant instead of a very variable function of the time, and the result is an instrument which is mechanical and little else, and can only be played with an unnecessary expenditure of energy.

I have heard a professional pianist perform a very delicate pianissimo passage in which the accented notes rang out clearly and brilliantly above the background without being played any louder. It was simply a difference of tone quality produced by a corresponding difference of touch. My dynamicallycontrolled piano-player is quite capable of giving a

very approximate reproduction of this effect, whereas I have heard an expert break down hopelessly over a similar passage at an exhibition recital of a commercial machine..

With regard to the connection between tone quality and touch, I do not think Dr. F. J. Allen's explanation meets the case. Unless there is distinct experimental evidence to the contrary, I do not think we ought to exclude the possibility of a double or multiple impact between the hammer and string; indeed, some of my experiences favour this hypothesis. But I am inclining more and more to the belief that the differences may be largely due to the elasticity and inertia of the stem of the hammer. The introduction of these elements converts the hammer into a dynamical system capable of independent vibration. The method of normal coordinates then enables us to represent this system by a simpler system having the same vibration periods; for example, a system of two or more particles connected by elastic springs and moving in a straight line. It is clear that the duration of contact of a pair of such particles with the wire will depend largely on the state of compression between them and their relative velocity at the instant of impact. The interval between the release of the hammer and its striking the wire is probably short compared with the time of a free oscillation of the hammer itself, and certainly short compared with the time in which such an oscillation would die out. On setting the hammers of the horizontal piano low down, the variations of tone quality entirely disappear, as one would expect.

I find another favourable condition by developing Kaufmann's method in connection with the problem of a single inelastic particle striking a wire near one end. The duration of contact is determined by the vanishing of a function which has one or more minimum values before it actually vanishes, some of these being small. A very small difference in the assumed conditions might therefore convert one of these minimum values into a negative value. Remembering that such assumed conditions are probably not even approximately satisfied in practice, we still have a result indicating that the pianoforte hammer and string may be highly susceptible to any cause which tends to vary their duration of contact.

I am specially pleased to receive Dr. Heaviside's views on this subject, and to find that he has been long interested in these difficult problems.

Since writing this I have read Prof. Morton's letter, and am very glad to receive his references to previous work on the subject. With regard to his own experiments, I think something more is necessary for my purpose than what he mentions in NATURE, namely a comparison of the striking velocities of pianoforte hammers in different parts of the scale. I notice Prof. Morton does not mention what particular notes were struck in his observations. It would also be important to compare the striking velocities for two notes, one in the treble and one in the bass, when simultaneously excited by a common pneumatic impulse of long or short duration, such as can be produced in these piano-player experiments with properly cut chords. With regard to the other question, I think it is unfortunate that authors like Matthay have used the terms "good" and "bad" touch in this connection. I freely admit that the heavy, inelastic impacts produced by the inexperienced performer produce such a harsh effect as to be very objectionable (and possibly this may be due to Dr. Allen's so-called "xylophone" effect); on the other hand, any playing sounds to me mechanical which does not involve considerable variation of tone quality. This appears to me to be particularly necessary in studying piano arrangements of orchestral music, where the sharp,

metallic tones of the brass instruments have to le brought out in contrast to the softer tones of: strings. Possibly when fingers are used the pian usually has too many other matters requiring .. attention. But whether a metallic effect is or "bad" must depend on how and when it is u. and personally I should think a constant tone quar the worst effect of all. Prof. Morton's letter, hos. ever, raises a number of other questions which wou take a long time to answer, and may have to explained in subsequent correspondence. G. H. BRYAN

Plâs Gwyn, Bangor, North Wales.

Mackerel and Calanus.

WE all believe that most of our common food-fishat some stage of life feed upon plankton, but the who have looked into sea-fisheries questions know tha there is a great want of actual observations connextir, the occurrence of some planktonic organism in qua tity with the presence of a particular fish. Cons quently the following record may be of interest to b.ch. marine biologists and fisheries experts.

We are out on a scientific fisheries cruise, and addition to members of my own family, two w known naturalists, Prof. Newstead and Mr. Alfred ( Walker are with us on the yacht, and we have ju had what we regard as a satisfactory demonstratior of the connection between a large shoal of mackere and the occurrence of Calanus finmarchicus in unusual quantity.

On arriving in this bay last night we found th the local boats had been catching abundance mackerel close to. We bought some for supper (god fish for a halfpenny each), and on dissection found that the stomachs of all of them were crammed tul of fresh-looking Calanus (the individual Copepod being for the most part distinct and perfect), along with a few immature Nyctiphanes and larval De pods. Prof. Newstead and my daughter then notics! while fishing over the side of the yacht, about 8 p.m., that the gulls in the bay were feeding in groups around patches of agitated water evidently caused by shoals of fish. On rowing out to these we saw ditinctly the mackerel, large and small, darting about in great numbers in the clear water, and we als noticed every here and there on the smooth surface of the water-it was a beautifully calm eveninginnumerable small whirls or circular marks which, ra looking closely, I found to be caused by large Co. poda close to the surface.

About twenty years ago I sent a note to NATURE, from the yacht Argo, in regard to large Copepoda il think it was Anomalocera on that occasion, and the locality was further north, off Skye) splashing on the surface so as to give the appearance of fine rain; and this present occurrence at once reminded me of the former occasion, but here the Copepod was Calan: › finmarchicus of large size and in extraordinary abun ance. They could be clearly seen with the even leaning over the side of the boat, a small glass collecting jar dipped at random into the water brought out twenty to thirty specimens at each dip, and a coarse grit-gauge tow-net of about 34 cm. in diameter caught about 20 cubic centimetres of the Copepoda in to minutes. The mackerel were obviously darting abut, occasionally leaping to the surface (which gave the gulls their opportunity) where the whirls caused br the Copepoda were thickest, and an examination of the stomach-contents of the fish on the yacht afterwards showed us that the amount in one macke was about the same quantity as that caught by t tow-net in five minutes. Prof. Newstead and I hav made a count of 8 c.c. of the tow-net gathering, and estimate that it contains about 2400 specimens

Calanus. This would give about 6000 Copepods in the stomach of an average mackerel, or in a five minutes' haul of the tow-net, on this occasion.

It may be added that these mackerel were evidently not being nourished in accordance with the views of Putter, and were clearly able to fill their stomachs from the plankton around them.

W. A. HERDMAN. S.y. Runa, Tobermory, N.B., July 12.

Helium and Neon.

THE experiments communicated to the Chemical Society recently by Prof. Collie and Mr. Patterson, the lectures delivered by Sir J. J. Thomson, and the discussions which have taken place in NATURE, on the possible synthesis of the chemical elements have aroused great interest outside England. So far as I can ascertain, opinion is much divided. For my own part I may perhaps be permitted to say that I have always entertained the idea of a possible formation of elements of the helium group from other gases by integration, just as these are formed from other elements by disintegration (see Chemical News, 1896, and Berichte, 1899). When I put forward this view objection was taken that 4H is greater than He, 4032 instead of 3.99, and the same kind of objection may be raised to-day that He+O, or 39+16, is less than Ne, 20-2 (unless Ne is a mixture of gases).

In order that the above question might be solved definitely, I would beg to suggest that experiments -hould be conducted in Röntgen-tubes from the electrodes of which every trace of the gases occluded

or firmly held by them would be first removed by continued bombardment with kathode rays.

As regards the question put forward by Sir J. J. Thomson, whether the new gas X, discovered by Sim, may be a new element that fills the vacant space in VII. group, 1 series (VII-1), in Me deléeff's periodic system, I may be allowed to remark that Mendeléeff's prediction of the properties of the elements Sc, Ga, Ge, could be successful, because it as an interpolation; whereas the prediction of the properties of the element X=3 includes an extrapolation, which is always rather uncertain; besides, the gases of the helium group were unknown at the time of the prediction. Its properties may be derived from the following equations:-(1) Ne: F=He: X; (2) L: F=H:X; (3) Li: H=F:X;

but also

Fe: He Mn: X, and (5) Cu: H= Br: X, showing how uncertain the prediction of its properties becomes, so that it is indeed probable that it will be more negative than fluorine, but not necessary that the gas should combine with the silicon of the glass. The delicacy of Sir J. J. Thomson's new method has superseded our old methods of investigation in a way similar to that based upon radio-activity, and the results of the study of the new gases discovered by this new method are awaited by chemists with the greatest interest. BOHUSLAV BRAUNER.

Bohemian University, Prague, July 6.

Red Water and Brine Shrimps.

By the kindness of Mr. A. W. Sheppard and Prof. A. Dendy, F.R.S., I have been enabled to examine specimens of the brine shrimps from Geelong mentioned by Mr. Whitteron in his letter (NATURE, June 12, p. 372). They belong to the species Parartemia setziana, described by the late Mr. O. A. Sayce in 1003 (Proc. Roy. Soc. Victoria, xv., part ii., p. 232). In Parartemia the unpaired uterine sac is produced into two large dorso-lateral lobes lying on either side of the "tail," and appearing, as Mr. Whitteron says, like the egg sacs of Cyclops." Mr. Sayce's speci

mens were obtained from a "brackish-water swamp near Lake Alexandrina, South Australia." It is interesting to learn that the species is able also to live in the brine of salt-pans.

The flagellate described by Mr. Whitteron is probably allied to, and perhaps identical with, Dunaliella salina, which has long been known to cause a red coloration in the brine of salt-pans in Europe and Algeria. A detailed account of this form and references to the somewhat extensive earlier literature of the subject are given by Clara Hamburger ("Zur Kenntnis der Dunaliella salina," Arch. Protistenk., vi., 1905, p. 111). W. T. CALMAN.

British Museum (Natural History),
Cromwell Road, London, S.W., July 12.

The matter usually presents itself to students rather differently. The predominant fact is the floating power of ice. Hereby the water is screened from further attacks of the cold air, and dispersal is provided in the puzzling conditions of ground or anchor ice. Next perhaps in importance is the slow conduction of cold by water. Then comes the large value of the latent heat of water. It is not obvious why there should be disastrous results if the maximum density of water were at o° C. The four units may be viewed as a helpful margin of safety rather than as an essential; but they would appear to be negligible in comparison with the 79 units of latent heat. Water at o° C. is by no means unstable; each gram weight as it passes into ice throws out amongst its neighbours an amount of heat which is an effective safeguard against sudden and extensive solidifying. W. B. CROFT.

The College, Winchester, July 5.

Radio-activity and the Age of the Earth.

poten

I AM gratified to learn from Dr. Fermor's letter in NATURE for July 10 that there is a scientific possibility of conceiving how the interior of the earth may be devoid of radio-activity. But if "high pressure and temperature" can inhibit the dissociation of " tially radio-active" substances, will they not do so also in the interior of the stars? If so, radio-activity will no longer be available to prolong their radiation of energy, and we shall be back in the old difficulty about the age of the sun. Indeed, it will be aggravated, because we now have positive evidence for a high antiquity of the earth, while still unable to explain that of the sun. F. C. S. Schiller. Corpus Christi College, Oxford, July 1I.

THE GENERAL MAGNETIC FIELD OF THE SUN.1

THOSE who are familiar with Prof. Hale's

brilliant discovery of magnetic fields in sunspots, and are aware of the difficulties connected with that investigation, will greatly admire his courage in seeking to establish the much weaker general magnetic field of the sun itself. The following condensed account of the method adopted and results obtained is given, to some

Based upon an advance proof of a paper by Prof. G. E. Hale which is to appear in The Astrophysical Journal.