arrived at the conclusion that these plants always freed the atmosphere from the "fixed air" (carbon dioxide) emitted by animals and emitted " dephlogisticated air" (oxygen), and Scheele believed that they always added to the amount of the "fixed air."

Jan Ingen-Housz was born at Breda, in Brabant, South Holland, on December 8, 1730, and attended the higher school there until the age of sixteen, after which he continued his education in the Universities of Louvain, Leyden, Paris, and Edinburgh, even after he had graduated (at the age of twenty-two) in Louvain. From 1757 to 1765 he practised medicine in Breda, but, after the death of his father, he went to London, on the invitation of Sir John Pringle, the King's physician. Here he became acquainted with distinguished anatomists and medical men, and made a study of the method of inoculation for smallpox. From London he went to Vienna, by the wish of the Empress Maria Theresa, and introduced the use of inoculation there.

Ingen-Housz approached the research which has brought him most fame the relation of plants to the atmosphere-from the standpoints of the physicist and chemist rather than the botanist, and with a view to the value of green plants exposed to daylight as purifiers of the atmosphere from the products of animal respiration. He had busied himself with the physical problems of electricity, magnetism, optics, and heat, and had made useful contributions to their investigation. His researches in chemistry led to improvements in the preparation of matches and in other matters of practical value.

A very valuable advance in microscopical technique introduced by him was the use of a cover over the drops of water or other fluids in which the objects were included for examination. At first the covers

were made of mica, but soon he employed thin glass covers, as is now the custom.

His researches into the nutrition of plants were for the most part carried on during his stay in Vienna, although his first work on the subject was published in London in 1779 under the title "Experiments upon Vegetables, discovering their great Power of Purifying the Common Air in the Sunshine, and of Injuring in the Shade and at Night." It was soon issued in German and Dutch translations.

When Ingen-Housz began the researches that led him to such great results it was generally taught that plants extracted from the soil the materials of which they were in want in the conditions in which they exist in the plant, and that nothing of importance required to, or did, pass off from plants. That gas was given off had been determined by Priestley and

Ingen-Housz succeeded in showing that both these eminent chemists were right in part, the green parts in daylight emitting "dephlogisticated air," while parts not green at all times, and even green parts in darkness, like animals, emitted "fixed air." His views were combated, even Priestley joining in attacking them, and by his authority preventing their importance from being recognised as it deserved to be. The new foundation for chemical investigation afforded by Lavoisier's discoveries was made use of by Ingen-Housz to explain more fully the nutrition of green plants than had been possible until the recognition of the composition of the "dephlogisticated air" and the "fixed air, " and he showed that the carbon contained in plants is derived from the carbon dioxide of the atmosphere instead of from the soil as had been supposed by Senebier. He also showed that the carbon could be acquired by green plants only in light, and that carbon dioxide beyond a limited degree of concentration in the atmosphere proved harmful even to plants as well as to animals. He thus distinguished between the respiration and the assimilation in plants, a distinction not fully realised or taught by botanists until many years later. The value of humus and of vegetable manure as food for plants he ascribed, not to the substance being directly employed by the plants as food, but to its effect on the mineral contents of the soil, which were rendered more easy of absorption, and he demonstrated that diluted mineral acids produced similar beneficial effects. His later views on the nutrition of plants are given in " 'An Essay on the Food of Plants and

the Renovation of Soils," which is contained in a collection of essays (in which it is No. 3) issued under the title "Additional Appendix to the Outlines of the Fifteenth Chapter of the Proposed General Report from the Board of Agriculture on the Subjects of Manures," London, 1796.

An appendix stating the sources of information about Ingen-Housz, with extracts from letters and a bibliography of his writings, adds to the value of the volume, and supports Prof. Wiesner's claim that he must be classed among the founders of botany, and gator in physics and in medicine. that he showed singular ability also as an investi

amination of only a few common pigments, and by no means exhaustively even with these; about some vehicles and diluents the information to be found in these pages is less meagre.

There are five chapters in this book, an appendix containing thirteen tables, and an adequate index. Chapter i. is devoted to the determination of certain constituents of common paints, and deals with aluminium, barium, carbon dioxide, chromium, iron, lead, magnesium, manganese, silicon, sulphur, and zinc. In this chapter, which occupies only fourteen pages, we are struck with the inadequate, and even puerile, drawing of the CO, apparatus shown in the figure on p. 3, and with the confused nomenclature

of the two oxides of chromium. For example, on pp. 4 and 5 we are told that "all chromate compounds must be changed into the chromic state which is indicated by an intense green color," and that this “green color is due to chromic salts." The omission of any caution as to the non-volatile impurities commonly occurring in the hydrofluoric solution used in ascertaining the purity of silica is unfortunate.

The properties of a few common pigments, such as Prussian blue, ultramarine, ivory-black, umber, Vandyke brown, the mixture of lead chromate and Prussian blue wrongly called chrome green, iron-red, genuine and imitative vermilion, a number of white pigments or adulterants, chrome yellow, red lead, yellow ochre, and the siennas are dealt with. This list serves to show how many of the finer and choicer pigments, namely, aureolin, cadmium yellow, viridian, and cobalt-blue, are excluded from consideration. Nor can we agree with everything we find in these pages. Ivory- and bone-black are not "combinations of carbon, hydrocarbons, water and mineral matter." Graphite does not possess a brownish gray "colour; and there are many words wrongly spelt in this chapter, such as analine for aniline, and limionite for limonite.

The examination of actual paints, and of such as are mixed ready for use, is dealt with in the third chapter. The preliminary treatment of oil-paints necessary before they can be tested or analysed is duly described. Chapter iv. is concerned with the matching of samples, while the final chapter is devoted to vehicles. Here will be found a more adequate, detailed treatment of the subject. On pp. 89-92, for instance, the curious drying oil called Chinese wood oil is described. This oil is used largely both in China and Japan, and is imported into America and Europe in increasing quantities. It is obtained from the seeds of Aleurites Fordii (Hemsley) and of other species of the same genus, as A. cordata and A. trisperma. Mr. C. H. Hall states (loc. cit.) that this oil, if heated to 285° C. to 300° C., suddenly solidifies into a jelly which is no longer soluble in the usual solvents, and cannot be reduced again to the liquid state. Mr. Hall's statement that Chinese wood oil, even in small proportion, confers upon paints the property of drying without gloss, and may be used as a substitute for wax in painting media intended to produce a dull or matt surface, seems to merit particular attention.

The thirteen tables of constants, coefficients, and specific gravities which constitute the appendix to this volume will be found useful by the analyst. There is a full index.

This little book, with all its imperfections and its immaturity, is not destitute of merit.

OUR BOOK SHELF.

British Rainfall, 1905. (Forty-fifth annual volume.) By Dr. Hugh Robert Mill. Pp. 271. (London : Edward Stanford, 1906.) Price 10s.

THE forty-fifth issue of this annual volume tells us healthy and active state of this voluntary rainfall better than any mere description could do of the organisation. When it is considered that more than 4000 individuals scattered over the British Isles read their rain-gauges at 9 o'clock every morning, enter their results on a form, and send in monthly returns to the central bureau at 62 Camden Square, and do band of enthusiasts for their united efforts in all this voluntarily, it is impossible not to admire this good a cause.

SO

The valuable collection of rainfall statistics is not, however, allowed to lie idle, for the energetic head of this organisation, Dr. H. R. Mill, with his small staff, brings all the facts together, and discusses the distribution of this rainfall both in space and time.

The present volume shows how well this work is carried out, and the observers must feel a great amount of satisfaction in seeing their united efforts so ably handled. Fronting p. 64 is a map indicating the positions of the 4096 rain-gauges at present in use, and one can see at a glance the districts where observers are urgently needed. Ireland and north and central Scotland are conspicuously in need of more volunteers, and it is hoped that many of the places mentioned in the text will soon be counted among the recording stations.

As meteorological readers of NATURE are fully acquainted with the general arrangement of the matter in these annual volumes, it is only necessary in this notice to direct attention to some of the discussions on the collected statistics. Thus, after a brief review of the recent important publication on the "Precipitation in the North German River Basins, compiled by Prof. Hellmann, we are presented with some valuable data on the relation of

evaporation from a water surface to other meteorological phenomena. The section on heavy falls on rainfall days in 1905 will be found very interesting reading, and the numerous maps show at a glance the distribution of these falls over the country. After sections dealing with the distribution of rainfall in time, and a discussion of monthly rainfall, we come to the relation of the total fall of rain in 1905 to the average. To sum up in a few words the result of this discussion, it may be said that for the whole of England and Wales the general rainfall for 1905 was 16 per cent. below the average. In fact, so low was this figure that " except for 1902 and 1893 there has able drought of 1887." It will be interesting to see how the present vear's rainfall statistics compare with those of 1905. In 1905 Scotland as a whole had a deficiency of 5 per cent., while Ireland suffered to the extent of 12 per cent.

not been so dry a year in England since the memor

Technical Thermometry. Pp. ix+62. (Cambridge: The Cambridge Scientific Instrument Co., Ltd., 1906.) THIS pamphlet contains detailed, illustrated descriptions of the various types of instruments for temperature measurement made or sold by the Cambridge Scientific Instrument Co., which has long been in the front rank in the manufacture of electric thermometers of all kinds.

It deals first with the well-known platinum resistance thermometers of the Callendar-Griffiths type. These are made in many different forms. Among the most interesting of the apparatus used in connection with them is the ingenious direct-reading temperature indicator, which gives without any calculation the direct centigrade or Fahrenheit temperature on the air-scale, with a sensitiveness of considerably less than 1 up to 1200° C. The various types of resistance-boxes used in accurate platinum thermometry are all arranged to be capable of self-verification. We believe that this self-testing type of resistance-box was among the first examples of a high-class physical instrument intentionally arranged by the makers to encourage periodical standardisation by the rather than complete dependence upon the original adjustment. The Callendar recorders, in their various forms, can now be made to give with very low energy consumption continuous records of resistance, temperature, radiation, E.M.F., current or power within very wide limits.

user

Among the thermoelectric appliances is a new form of recording millivoltmeter, in which the galvanometer boom is depressed every half minute on to an inked thread, thereby leaving a dotted record on the paper. The instrument can be made sufficiently sensitive for recalescence curves. The radiation pyrometers of Prof. Féry are also described and illustrated. In these the radiation from the object the temperature of which is to be measured is concentrated upon a minute thermocouple at the focus of a mirror or lens, and the E.M.F. set up is measured in the ordinary way by a suitable millivoltmeter.

In an appendix are given an excellent summary of the principles of electric thermometry with tables of constants, and a list of trustworthy melting and boiling points obtained from the National Physical Laboratory; also a good bibliography of recent thermal research.

Astronomischer Jahresbericht. Band vii. Literature of 1905. By A. Berberich. Pp. xxxvii+646. (Berlin: Georg Reimer, 1906.) Price 20 marks. THIS Volume is the seventh issue of a series of most useful compilations, and it is a matter of deep regret that the founder and chief worker of such an

on

admirable publication is no longer with us. Herr Walter Friedrich Wislicenus died last year October 3, but, as we are told by Dr. Walter de Gruyter in a brief obituary notice, he contributed a considerable portion of the present volume. The frontispiece to this issue, therefore, fittingly presents us with an excellent portrait of the founder, whose place is now taken by Herr A. Berberich.

With regard to the book itself little need be said, except that the high standard of former years has been maintained. The 600 pages of references, with their brief and concise abstracts, cover the domain of astronomical literature for the past year, and a very complete name index concludes the volume.

It may

be incidentally remarked that the total solar eclipse of August, 1905, is responsible for no less than ninetyfive references, which help somewhat to increase the bulk of the present volume.

Zoologischer Jahresbericht für 1905. Herausgegeben von der Zoologischen Station zu Neapel. Redigirt von Prof. Paul Mayer. (Berlin R. Friedländer und Sohn, 1906.) Price 24 marks.

THE always welcome "Naples Jahresbericht " appears, as usual, well up to time, and its familiar features remain unchanged. Purely taxonomic papers are not included in the programme, but this limitation has been generously interpreted by some of the recorders. Where we have been able to test the lists we have found them full and accurate, and many of the summaries are models of terseness and clearness. If we look at the first section we are at once struck with the rapidly increasing number of important researches on the Protozoa; if we look at the last section we are similarly impressed with the number of papers dealing with Mendelian phenomena. The indefatigable editor, Dr. Paul Mayer, is responsible for the reports on Protozoa, Bryozoa, Brachiopoda, on part of the Arthropoda, and on general biology-truly a heavy piece of work for a man who does so much else. To him and to his collaborateurs we offer in the name of zoologists our hearty thanks.

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.]

Absorption of the Radio-active Emanations by
Charcoal.

PROF. RUTHERFORD in his interesting letter in NATURE of October 25 (vol. lxxiv., p. 634) on the Absorption of the Radio-active Emanations by Charcoal" has no doubt quite unintentionally mistaken the general results of my experiments, and therefore I feel that some slight addition ought to be made to his communication.

In the first paragraph of his letter Prof. Rutherford says that "the interesting property of certain kinds of charcoal, notably that of the cocoa-nut, of rapidly absorbing gases, except the inert gases belonging to the argon family, is now well known since the recent experiments of Sir James Dewar."

Now, the statement made in the part of the paragraph I have italicised is not accurate. In my papers entitled "" The Absorption and Thermal Evolution of Gases Occluded in Charcoal " (Proc. Roy. Soc., 1904), "The Separation of the more Volatile Gases from Air without Liquefaction (Proc. Roy. Soc., 1904), "Nouvelles Recherches sur la Liquefaction_de l'Helium " (Comptes rendus, 1904), and "New Low Temperature Phenomena (Proc. Roy. Inst., 1905), I have shown that all the inert gases without exception can be condensed in charcoal as effectively as ordinary gases provided corresponding conditions of temperature, pressure, and concentration maintained.

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are

In speaking of the many avenues for future inquiry opened up by the charcoal method of separating gases, I said (Proc. Roy. Soc., p. 130, 1904): The method I have described will be equally applicable to the treatment of the gaseous products from minerals containing helium, hydrogen, &c., and also to the radium products of the same kind. It seems even probable that the separation of the less volatile constituents in the air may be improved by a "" As a matter slight modification in the mode of working.' Society in 1904, I had made a few experiments on the of fact, at the time of these communications to the Royal

condensation of the radium emanation by charcoal in vacua, and also on the separation of krypton and xenon; but during the last two years my health has been so indifferent that many lines of investigation have had to be abandoned. In my Royal Institution lecture of June 6, 1905, I ex

plained and exhibited the process of separating krypton and xenon, showing that a proportion of less than a millionth of these constituents in the atmosphere can be condensed and concentrated in charcoal cooled to the temperature of liquid air. Turning again to Prof. Rutherford's letter, his surprise about the absorption of the emanation of radium, thorium, and actinium by charcoal on the ground of being inert gases may be dismissed as nothing more than what we should anticipate; but the temperature at which the absorption by charcoal takes place raises some important questions.

To take an illustration (Proc. Roy. Inst., 1905), I have shown that charcoal cooled in solid carbonic acid at the temperature of 195° ab. is capable for a time of absorbing the carbonic acid present in air (amounting to, say, 3/1000 of an atmosphere) until the concentration rises to about 1 per cent. of the weight of the charcoal. If, on the other hand, the separation of the carbonic acid from the air had to be done by cooling alone, then the temperature of the air must be reduced below 129° ab., and about 100° ab. it would for practical purposes be nearly all removed. Thus charcoal about twice the absolute temperature required for condensation by mere cooling is for a small concentration of the gas undergoing absorption equally effective. We can compare ΠΟΥ the behaviour of the radium emanation with that of carbonic acid. In the paper of Rutherford and Soddy on the condensation of radio-active emanation (Phil. Mag., 1903) it is shown that the temperature has to be lowered below 138° ab. in order to condense the radium emanation, while it is complete by 123° ab. By analogy, therefore, we anticipate that at twice 138° ab. charcoal would still act as a condensating agent. This, then, brings us up to about the ordinary temperature, just what Rutherford has found to be sufficient. Such comparisons, however, may not necessarily mean that the radium emanation is comparable in volatility with carbonic acid at low temperatures.

If we

The results of Rutherford and Soddy would seem to show that the radium emanation has a high latent heat of volatility, and consequently by all analogy a high boiling point. Thus they say (Phil. Mag., 1903). that the radium emanation begins to volatilise at 118° ab., and by 119.5 ab. the amount is increased four times. accept the view that the partial pressures of the emanation were in the ratio of one to four at the two temperatures given above, then we may apply the Rankin formula (log P-A-B/T, where A and B are constants, P the pressure, and T the absolute temperature) and find the order of the value of the B which is proportional to the molecular latent heat, which in this case comes out 5662. Taking, again, the relative electrometer leaks by the statical method of 5, 3 at 126°.5 ab. and o, 74 at 1245 ab., this gives 6735, which is of the same order of magnitude. The following values of the B constant for different bodies are useful for comparison :

The calculated value of the B constant of the radium emanation is, then, twice the value for mercury and nine times the value for xenon. We need not press, however, the accuracy of the latent heat constant of the radium emanation too far, so let us divide it by two, which will make it of the order of the latent heat of mercury or phosphorus. Accepting for the moment such a value of the molecular latent heat, we cannot avoid inferring that the boiling point of the emanation may be relatively higher than one at first might anticipate. Even if we assume that the emanation represents a gas two steps higher in the periodic series than xenon, the B constant would by analogy be only a little more than 1000. The latent heat argument supports the view that the molecular weight of the emanation must also be high, and of the order of 200 or above it. Naturally the theoretical argument based on the value of the latent heat constant fails if it is not legitimate to

FULLER consideration of the experimental evidence on the effects of concentration on the activity of radium convinces me that, on the whole, this is certainly against the a priori probable assumption that a large part of the activity is not spontaneous. I refer more especially to Prof. Rutherford's experiment on dilution, as touched on in my letter in NATURE of October 25. Other considerations lead to the same view.

The conclusion at issue is, however, too important to be left on the existing experimental basis. J. JOLY. Geological Laboratory, Trinity College, Dublin.

The Evolution of the Colorado Spiderwort. UNTIL recently the name Tradescantia virginiana, of Linnæus, was made to include a multitude of forms, without discrimination. However, as we go from east to west we observe a marked change in the spiderworts, corresponding with an equally marked change in climate. The more eastern forms of moist regions are tall and rank, with bright green foliage. The true virginiana has the pedicels and sepals villous, the hairs not glandular, and does not in any way suggest a xerophyte. In the middle west are two forms, T. occidentalis (Britton), bright green, but with narrow leaves and usually smaller flowers, the pedicels and sepals with gland-tipped hairs, and T. reflexa, Raf., glaucous, the pedicels glabrous, the sepals with a tuft of hairs at the apex. The latter is more especially southern,

and is said to extend even to Florida. Still further west we find in New Mexico another form, T. scopulorum, of Rose, slender and much branched, glaucous, with glabrous pedicels and smooth sepals. Still again, we have in Colorado a distinct plant, which I have named T. universitatis.' This is strongly glaucous, robust, but not very tall, pedicels glabrous, with a very few gland-hairs, sepals glandular-pilose. The leaves are broad (the sheathing bases 12 mm. to 13 mm. wide), and the flowers are about 35 mm. across. There is no sign of any tuft of hairs at the apex of the sepals.

2

In all this we have a series of changes, not always simultaneous, from bright green to glaucous, and from simply villous pubescence to gland-tipped hairs. In some cases the leaves become narrower and the flowers smaller. It is easy to see in all this direct adaptation to drier conditions, but it is not so easy to determine how it came about, or how far it may result from immediate influences modifying individuals of a plastic type. At Boulder, Colorado, the T. universitatis is a plant of spring and early summer, and has the characters just referred to. This year, however, a ditch was dug right through a place where the plants abounded, and many of them were covered up by the earth thrown out. To-day, September 30, I find that these plants have managed to sprout through the covering soil, and are now in full bloom. They are typical, except in one conspicuous character-the pedicels and sepals both are profusely gland-hairy. If one received these specimens, with the mere statement that they were gathered on the last day of September, noticing the profuse pilosity as well as the unusual time of flowering, one would readily take them for a distinct thing.

There seems to be some confusion about the plant originally named occidentalis by Britton. As first described, it was said to have narrowly linear leaves, and the first locality cited was Wisconsin. Rydberg, in his recent "Flora of Colorado,' gives it a quite different range, no further east than Nebraska, and makes it include the Colorado plants. The name must go, however, with the plant originally described. T. D. A. COCKERELL. University of Colorado, Boulder, Colorado, September 30.

1 Type locality, the Campus of the University of Colorado, at Boulder. Also common on the Campus of Colorado College at Colorado Springs. 2 And, in part, more saline soil?

THE DYNAMICS OF BOWLING.1 FOLLO OLLOWING up their interesting volume on "Great Batsmen," the accomplished authors of "Great Bowlers and Fielders" have practically completed all that action photography can teach us regarding the methods of great cricketers. The present handsome volume with its 464 action photographs registers for all time the successive positions of the body in the act of bowling of some of the most celebrated bowlers of our day, and also certain very characteristic attitudes of a number of our best fielders. From the purely cricketing point of view the book must ever be of the most enthralling interest, not because it establishes any fundamentally new principle in the art of highclass bowling, but because it proves the wonderful variety of method by which different individual bowlers effect practically the same result. The movements of the body, arm, wrist, hand, and fingers are all coordinated to the one end of imparting to the ball a definite combination of translation and spin. It does not always happen that the bowler hits off the exact combination aimed at, but when he does the future progress of the ball through quiet air and off a good pitch is absolutely definite. There is no difficulty in understanding the dynamics of the "break"; the problem is simply that of a rotating sphere impinging obliquely on a rough surface, and is familiar to everyone who has handled a billiard cue with intelligence. The point of interest to the would-be bowler is how it is effected. This is discussed at considerable length in distinct parts of the book contributed by Messrs. F. R. Spofforth, B. J. T.. Bosanquet, and R. O. Schwarz. The introductory chapter by the "Demon

Bowler " (to whom the book is dedicated) is capital reading. It is, indeed, rather to be studied than read, and the same remark applies to Mr. Bosanquet's lucid and scientific discussion of the breaking leg-break."

off

to

At the very outset it is obvious that no bowler can give to a cricket ball anything like the combined velocity and spin which can be so easily communicated to a golf ball, or even a tennis ball. The comparative lightness of the latter enables the player to give it sufficient spin (with velocity) so as to call into action the differential air pressure, producing evident swerve. Tait, in his discussion of the golf-ball flight, showed that this swerving force (which

with the horizontal, it is clear that there is very little chance of a cricket ball beginning its swerve to right or left for the same reason that a golf ball is sliced or pulled. How, then, is the swerve to be explained? The matter crops up at intervals throughout the book, and is discussed at some length by Mr. Spofforth; but with all due regard to his authority as one of the greatest bowlers of all time, it is difficult to accept his explanation as in every respect sound. He says that " a ball which has check spin (that is, under-spin) on it, loses it through friction against the air during its flight; at the moment this occurs the ball slips the cushion of air it has made, especially in between the seams. What leads me to

acts at right angles to the plane containing the velocity and the axis of spin) may be taken as being proportional to the product of the translational and angular speeds. He estimated that it might attain a value equal to about four times the weight of the ball. In the case of the cricket ball it is doubtful if the deviating force due to air pressures acting on the progressing and rotating ball could ever become more than a small fraction of the weight. Then, as the rotation takes place in all over-hand delivery about an axis which makes at the most a small angle

1 "Great Bowlers and Fielders. Their Methods at a Glance. By G. W. Beldam and C. B. Fry. Pp. xv+547; illustrated. (Macmillan and Co., Ltd., 1906.) Price 215. net.

this belief is that it is almost impossible to swerve unless the seam of the ball is up and down. The check spin keeps the seam vertical until the airresistance causes the spin to cease altogether. At this point, especially if the ball has an upward tendency and the earth's power of attraction is asserting itself, the swerve will be great. To swerve, the ball must have some spin on it, but not much. If it has great spin it will never lose it in time to swerve, and I maintain that at the actual time of swerving the ball has ceased to spin, or nearly so. Further on he says that he has never seen any bowler swerve with the wind," that a bowler swerves more while the ball is new," that he does

66