factor is biological. Search was therefore made for organisms fulfilling these conditions and numbers of protozoa were found. Definite evidence has been obtained that trophic forms occur as normal inhabitants of the soil, and the estimates of numbers so far available show that they are considerable. There is the closest possible relationship between the extinction of the protozoa and the extinction of the limiting factor, and also between the re-establishment of the protozoan fauna and the setting up of the limiting factor after reinfection with small quantities of soil.-Prof. W. M. Hicks: The enhanced series of lines in spectra of the alkaline earths. A discussion of the enhanced series of the alkaline earths is carried out in order to determine their relation to the sun. For this purpose the results given for Mg, Ca, Sr by Fowler in his recent Bakerian Lecture are used, and, in addition, the corresponding series in Ba and Ra are considered. It is found that the quantity A', giving the doublet separations, is given with great accuracy in terms of the oun, as follows:-Mg, 5618; Ca, 688; Sr, 588; Ba, 5648; Ra, 608; where & is four times the corresponding oun for the element. The satellite separations are also found as functions of the same quantity. Further it is shown that these series strongly support the general relations given in a former communication that the first p-sequence depends on a multiple of the atomic volume, and that the diffuse sequence is such that the denominators of the first lines, when the wave number is expressed in the form A-N/(den), are themselves multiples of A' or of the oun.-Prof. H. F. Baker Certain linear differential equations of astronomical interest. This paper is written to exemplify the application of a general method for the solution of linear differential equations given by the author some years ago. The method furnishes solutions in a form valid for an indefinitely extended region. It is here applied (1) to establish a result as to the convergence of the solution of a particular equation, apparently in disagreement with a conclusion reached by Poincaré in his "Méthodes Nouvelles de la Mécanique Céleste "; (2) to place the general method given by Laplace for the absorption of the time in astronomical series under trigonometrical signs in connection with the ordinary theory of characteristic exponents; (3) to discuss in general terms the oscillations of a dynamical system about any given possible state of motion; (4) to furnish a regular calculus for the solution of the equation used by G. W. Hill for the motion of the moon's perigee, and similar equations. The earlier part of the paper discusses particular equations from a less formal point of view, and has seemed necessary in order to place the matter in proper light. One particular problem discussed is that of the stability of three bodies of any masses moving in ellipses at the angular points of an equilateral triangle, a matter of which the discussion has recently been revived.-Prof. Karl Pearson: The partial correlationratio. The general theory of mutiple correlation has been long established, and is summed up in the discussion of two constants-the partial correlation coefficient and the multiple correlation coefficient. If there be m variates, 1, 2, 3... m, then the partial correlation coefficient of the (m2)nd order is related to the multiple correlation coefficients of the (m-1)th and (m-2)nd orders by the equation : The object of the present paper is to give the corresponding equation for show-regression. It is known that the value of the above relation is exactly commensurate with the linearity of the regression, a condition not synonymous with but embracing as a special The paper shows that there are only three independent first order partial correlation-ratios and gives the formulæ for these, and for higher order correlationratios in terms of the multiple ratios and lower order partial ratios.-S. Skinner and F. Entwistle: The effect of temperature on the hissing of water when flowing through a constricted tube. The experiments deal with the temperature coefficient of the effect described by Osborne Reynolds before the British Association at Oxford, 1894. It is shown that the velocity at which hissing just occurs between o° and 100° C. suffers a diminution which may be expressed by a formula V1 = c(t −0), where V is the velocity of the stream at a temperature t, and the critical temperature of water, and c a constant. It is argued that this result forms a measure of the tensile strength of the liquid, and consequently it brings the phenomenon of hissing into relation with the other properties of a liquid.J. C. McLennan and J. P. Henderson: Ionisation poten. tials of mercury, cadmium, and zinc, and the single and many-lined spectra of these elements. (1) It is shown that a spectrum consisting of a single line is obtainable for mercury, for zinc, and for cadmium. (2) The wave-lengths of these lines are, for mercury, λ=2536.72 A.U.; for zinc, λ=3075-99 Å.U.; and for cadmium, λ=3260-17 Å. U. (3) The minimum ionisation potentials for mercury, zinc, and cadmium are shown to be 49 volts, 3.74 volts, and 3.96 volts respectively. (4) Some considerations are presented which support Sir J. J. Thomson's theory of the two-type ionisation of atoms of mercury, and others which suggest that the theory is applicable as well to the ionisation of atoms of zinc and cadmium. (5) The minimum arcing potential differences which will bring out the manylined spectra of mercury, zinc, and cadmium vapours are found to be 12.5 volts, 11-8 volts, and 15-3 volts respectively. These voltages are also probably the minimum ionisation potentials of the second type for the atoms of these three elements. (6) Considerations are presented which suggest the possibility of analysing the spectrum of an element in such a way as to enable one to correlate different portions of the spectrum with disturbances in definite portions of the atomic structure of that element.-Dr. A. E. H. Tutton: The monoclinic sulphates containing ammonium.-Completion of the double sulphate series. In this communication are described the five remaining double sulphates of the series R,M(SO)..6H ̧O, in which R is ammonium and M is nickel, cobalt, manganese, copper, and cadmium. The present memoir completes the author's work on the double sulphates of this series. The main conclusions are the following (1) These ammonium salts are truly isomorphous with the similarly constituted potassium, rubidium, and cæsium salts of the generic formula above given. but are not eutropic with them; the potassium, rubidium, and cæsium salts alone form the exclusive eutropic series in which the crystallographical proper : ties (both morphological and physical) obey the law of progression with the atomic weight of the alkali metal which has been established in previous communications. This law is particularly well illustrated by the fact, to which no exceptions have been observed, that average change of angle between crystal faces, and also maximum change of interfacial angle (which exceeds two whole degrees), are directly proportional to change in atomic weight when any one alkali metal is replaced by another. (2) The dimensions of the space-lattice of any ammonium salt of the series are nearly identical with those of the intermediate rubidium salt, so that the two atoms of rubidium are replaced by the ten atoms of the 2NH, radicle-groups without appreciably altering the crystallographic structural dimensions. (3) The salts of the series in which R is thallium (also studied in a previous memoir) resemble the ammonium salts closely, in truly belonging to the isomorphous series, but not to the more exclusive eutropic series formed by the salts of potassium, rubidium, and cæsium. Like the ammonium salts, they also closely resemble the rubidium salts, but the thallium salts are distinguished optically, possessing transcendent refractive power, both their refractive indices and their molecular refraction being far higher than for any other salts of the whole isomorphous series.-E. B. R. Prideaux : General equations for the neutralisation of dibasic acids, and their use to calculate the acidity of dilute carbonate solutions.-Prof. H. A. Wilson: The electrical conductivity and luminosity of flames containing salt vapours.-T. R. Merton: A spectrum associated with carbon in relation to the Wolf-Rayet stars.-Sir Wm. Abney and Prof. W. Watson: The threshold of vision for different coloured lights.-Lord Rayleigh: Hydrodynamical problems suggested by Pitot's tubes.Prof. M. C. Potter: Electrical effects accompanying the decomposition of organic compounds. II.Ionisation of the gases produced during fermentation. -Prof. E. W. MacBride and A. Jackson: The inheritance of colour in the stick-insect (Carausius morosus). -Sir Francis Darwin: The relation between transpiration and stomatal aperture.-D. M. S. Watson: The monotreme skull-a contribution to mammalian morphogenesis. Mineralogical Society, June 15.-Dr. A. E. H. Tutton, president, in the chair.-G. M. Davies: Detrital andalusite in Cretaceous and Eocene sands. Detrital andalusite is not confined to Pliocene and later deposits as was formerly supposed, but is a frequent constituent throughout the Cretaceous and Eocene beds of the south-east of England. In the lower Cretaceous beds it is still perfectly fresh, and shows no signs of instability under the influence of meteoric water.-J. F. N. Green: The garnets and streaky rocks of the English Lake District. Certain peculiar rocks occurring in the Lake District are characterised by almandine garnets and parallel streaks of secondary minerals. The capricious distribution of the garnets in diverse rock-types was considered to exclude originality, and thermal or dynamic alterations were shown to be inadequate. Circulating solutions under pressure during the solfataric stage of the Borrowdale episode were suggested as the agent, and illustrations were given of the replacement of felspar by garnet in Lake District rocks. The same origin was assigned to the streaky infiltrations which frequently contain pyrites or garnet.-Dr. S. Kôzu: The errors in the angle of the optic axes resulting from those of the principal refraction indices determined by total reflection. The indices so found are correct within 0.0002 for sodium light. Assuming the error to be only half this, the extreme values of the angle are for anorthite, 76° 8-6', and 79° 21-8'; for albite, 76° 14.1 and 80° 46-9'; and adularia 56° 16-9′ and 65° 569'.-Dr. S. Kôzu: The influence of temperature on the optic axial angle of sanidine from the Eifel. Pockels has shown that in those rhombic crystals in which the axial angle varies considerably in the neighbourhood of zero the relations between the angle and the temperature is represented by a parabola. Sanidine from the Eifel very nearly approaches the conditions of a rhombic crystal. The values of 2E were determined for seven different wave-lengths. The plotted curves were found to accord with Pockels's statement; further, the complex curves for the various wave-lengths were identical.-Dr. G. T. Prior: The meteoric stones of Warbreccan, Queensland. Three stones, weighing respectively about 69, 64, and 1 lb., were known to the natives of central Queensland before 1904, and their fall was probably seen. were acquired by the British Museum in 1905. They are white-veined chondrites, and in chemical and mineral composition are similar to other members of the group.-A. F. Hallimond: Autunite. It is concluded that the Cornish material is essentially different from the Autun mineral, and the name bassetite is proposed for the former, the fundamental characters of which are:-Oblique, B=89° 17', a:b:c= 0.3473: 1:0.3456; forms, 010, 110, 120, OII, III, 121, 121, 141, io1; twinning by parallel growth of a and c axes, perfect cleavage parallel to oro, also 100, 001; yellow, transparent; biaxial, 2E=110°; pleochroic, pale to deep yellow; soluble in acids. They Linnean Society, June 17.-Prof. E. B. Poulton, president, in the chair.-The four following__papers were reports on materials brought home by Prof. J. Stanley Gardiner from the expedition to the Indian Ocean in H.M.S. Sealark in 1905-E. T. Browne: Medusæ from the Indian Ocean.-Prof. A. Dendy: (1) Report on the Hexactinellid sponges (Triaxonida); (2) Continuation (Tetraxonida).-J. C. Robson: The Cephalopoda obtained. PARIS. Academy of Sciences, June 21.- -M. Ed. Perrier in the chair.-J. Boussinesq: The extreme slowness of cooling in the deep parts of the earth's crust, and an attempt to estimate, starting from a certain period, the progress of the solidification.-Paul Brück: Observations of the Mellish comet (1915a) made at the Observatory of Besançon with the 33 cm. equatorial. Eleven positions of the comet are given for March 16, April 13, 15, 16, 17, May 14 and 15.-René Garnier: The representations of the integrals of the equations of M. Painlevé by means of the theory of linear equations.-M. de Broglie: The spectra of the homogeneous secondary X-rays. A claim for priority as regards a recent paper on the same subject by M. Glagolev.-E. Raverot A temperature interval regarded in relation to mechanical measurements. Starting with the numerical coincidence that the erg is 0-2381 × 10- calories, and the specific heat of air at constant pressure is 0-2382 calories, the joule (0.238 cal.) is defined as the quantity of calorific energy corresponding to a variation of volume of the mass of 1 gram of air of 1/273 of its volume at o° C., at the constant pressure of the atmosphere.-Léon Bouthillon: The charge of condensers by means of a constant electromotive force and their discharge in a spark circuit. Whatever may be the kind of spark-gap employed, the conditions under which a musical note is produced are the stable conditions under which the system is self-regulating. G. A. Le Roy: The measurement of the waterproof qualities of cloths and military fabrics. The percolating water falls on a dry filter paper impregnated with a salt, and establishes an electrical circuit. The apparatus can be made recording, and does not re quire watching.-J. Deprat: The modifications in the structure of the Fusulinidæ from the Dinantian to the end of the Permian.-Pereira de Sousa: The earthquakes at Algarve (southern Portugal) from 1911 to 1914. These appear to be of epirogenic origin.-B. Galitzine: The earthquake of February 18, 1911. This earthquake coincided with a great rock slide at Sarez, in the Pamir, which filled up the valley of Mourgab and transformed it into a lake. The author concludes that this rock fall was not the consequence, but the cause of, the seismic disturbance registered at so many stations.-J. Clarens: The estimation of urinary acidity.-H. Busquet: The mode of action of colloidal gold the production of cardiac effects by particles of metal not in solution. From a study of the effects of the injection of colloidal gold into the dog and rabbit, it is concluded that the immediate effects on the heart cannot be attributed to gold in solution, but must be produced by the suspended colloidal particles.-H. Stassano The sterilisation of microbial cultures or emulsions by heat in thin layers.-Em. Bourquelot, M. Bridel, and A. Aubry Researches on the glucosidification of glycerol by B-glucosidose (emulsin). The product obtained by the biochemical synthesis contained two glucosides, differing in their rotatory power and resistance to the action of emulsine. Climbing Plants. By W. Watson. Pp. x+132+ plates. (London and Edinburgh: T. C. and E. C. Jack.) 2s. 6d. net. The Analysis of Non-Ferrous Alloys. By F. Ibbotson and L. Aitchison. Pp. vii+230. (London: Longmans and Co.) 7s. 6d. net. Bartholomew's New War Map of Italy and the Balkan States. (Edinburgh: J. Bartholomew and Co.) IS. net. The Poison War. By A. A. Roberts. Pp. 144. (London: W. Heinemann.) 5s. net. DIARY OF SOCIETIES. FRIDAY, JULY 2. GEOLOGISTS' ASSOCIATION, at 8.-A Provisional Hypothesis to Explain the Occurrence of the Various Types of Fossil Man: Prof. A. Keith. SATURDAY, JULY 3. ARISTOTELIAN SOCIETY, BRITISH PSYCHOLOGICAL SOCIETY, and the MIND ASSOCIATION, at 6.-Joint meeting. Mr. Bertrand Russel's Theory of Judgment: Prof. G. F. Stout. MONDAY, JULY 5. ARISTOTELIAN SOCIETY, BRITISH PSYCHOLOGICAL SOCIETY, and the MIND ASSOCIATION, at 4.-Joint meeting. The Import of Propositions: Miss Constance Jones, Dr. Bernard Bosanquet, and Dr. F. C. S. Schiller. CONTENTS. BOOKS RECEIVED. Lessons and Experiments on Scientific Hygiene and Temperance for Elementary School Children. By H. Coomber. Pp. xx+163. (London: Macmillan and Co., Ltd.) 1s. net. Indian Mathematics. By G. R. Kaye. Pp. 73 (Calcutta and Simla Thacker, Spink and Co.) Numerical Examples in Physics. By H. S. Jones. Pp. xii+332. (London: G. Bell and Sons, Ltd.) 38. 6d. Citrus Fruits. By Dr. J. E. Coit. Pp. xx+520. (New York: The Macmillan Company; London: Macmillan and Co., Ltd.) 8s. 6d. net. The Principles of Rural Credits as Applied in Europe and as Suggested for America. By J. B. Morman. Pp. xviii+296. (New York: The Macmillan Company; London: Macmillan and Co., Ltd.) 5s. 6d. net. The Mutation Factor in Evolution, with Particular Reference to Enothera. By Dr. R. R. Gates. Pp. xiv + 353. (London: Macmillan and Co., Ltd.) IOS. net. PAGE Our Astronomical Column: The Origin of Comets. Companions to Mellish's Comet The Aberration Constant and Latitude Variation 493 493 493 493 The Report of the Cambridge Observatory, 1914-15 493 The Destruction of Flies 493 The Analysis of Dyestuffs and their Identification in Dyed and Coloured Materials, Lake-Pigments, Foodstuffs, etc. By Prof. A. G. Green. Pp. ix + 144. (London: C. Griffin and Co., Ltd.) 8s. 6d. net. The Aeroplane. By A. Fage. don: C. Griffin and Co., Ltd.) Aero Engines. By G. A. Burls. Pp. x+ 196. (London: C. Griffin and Co., Ltd.) 8s. 6d. net. Laboratory Work for Coal-Mining Students. J. Sim and A. M. Wylie. Pp. viii+136. (London: E. Arnold.) 2s. 6d. net. Meteorology of Australia. Commonwealth Bureau of Meteorology. Results of Rainfall Observations made in Queensland, including all Available Annual Rainfall Totals from 1040 Stations for all Years of Record up to 1913, together with Maps and Diagrams. Pp. 285. (Melbourne: A. J. Mullett.) IOS. 6d. Staffordshire. By W. B. Smith. Pp. xi+155. (Cambridge: At the University Press.) IS. 6d. net. The Strength of Materials. By E. S. Andrews. Pp. x+604. (London: Chapman and Hall, Ltd.) Ics. 6d. net. Editorial and Publishing Offices : MACMILLAN & CO., LTD., ST. MARTIN'S STREET, LONDON, W.C. Advertisements and business letters to be addressed to the Publishers. Editorial Communications to the Editor. Telegraphic Address: PHUSIS, LONDON. Telephone Number: GERRARD 8830. THURSDAY, JULY 8, 1915. EMMA DARWIN AND HER CIRCLE. Emma Darwin: A Century of Family Letters, 1792-1896. Edited by her daughter Henrietta Litchfield. Vol. i., pp. xxxi + 289. Vol. ii., pp. xxv+326. (London: John Murray, 1915.) Price 215. net. Two vols. CURI URIOSITY as to the intimate life of those who have become distinguished is at any rate human. It may be that in some cases it would be better if the veil were not withdrawn. But there is a better reason by which such curiosity is justified. We want to know what were the conditions under which great personalities have been produced. These remarkable volumes will charm by their literary merit. But here they invite considerations of a more scientific kind. They give the history of three notable families which intermarried until they formed a sort of clan. The Allens were landed gentry of north of Ireland origin but settled in Wales; the Wedgwoods in Staffordshire and the Darwins in Lincolnshire were yeomen who rose in social rank, itself a note of racial ability. The relationships would be perplexing but for the pedigrees. All three strains were united when Charles Darwin married his cousin Emma Wedgwood. The men had plenty of fibre, sometimes a little too fibrous, the women no less charm and vivacity. John Allen had nine daughters; the eldest married the second Josiah Wedgwood; one Sir James Mackintosh, whom Darwin thought an even better talker than either Carlyle, Macaulay, or. Huxley, but whose misfortune was never to have red tape to tie up his bills; another was grandmother to Georgiana, Lady Salisbury; and still another was the wife of Sismondi, the historian. All families were well-to-do and "middle-class." But what a class it was; there was nothing like it at the time except the aristocracy at Geneva, with whom it was in touch through Sismondi and Madame de Staël. When Darwin married, a friend wrote: "It is very like a marriage of Jane Austen's, can I say more?" He could not, for the entire atmosphere was that of Jane Austen, wholesome, vivacious, intelligent. One of the Allen daughters made a penetrating remark à propos of an incident at Sydney Smith's: "In the gay world they commit more offences against the decencies of society than in the middle classes." But though well-to-do the middle class of the early nineteenth century was simple and and unaffected in its mode of life and content with intellectual pleasures. With leisure and freedom 66 from anxiety it could turn to science and recruited the Royal Society. This swept that body into the social life of the day, which is now inevitably ebbing away from it. Darwin speculates in a letter to a son as to "what makes a man a discoverer of undiscovered things," and remarks that 'many men who are very clever-much cleverer than the discoverers-never originate anything." He conjectures that "the art consists in habitually searching for the causes and meaning of everything that occurs." Perhaps the explanation lies in the difference between the inductive and deductive temperament. Hereditary aptitude must also count for something. The clan was clever enough but never failed to throw up originality. Tom Wedgwood was "the first discoverer of photography," Hensleigh was a mathematician and philologist, John with Sir Joseph Banks founded the Horticultural Society at Hatchard's shop, Sir Henry Holland and the Galtons were cousins. The amateur has been the glory of English science; there is now little place for him. The ground to be traversed before the fighting line is reached is too vast, and each worker must be content to "nibble" at his own little section with small knowledge of what the rest are doing. And So, rather unkindly, Prof. Armstrong describes the Royal Society as a "rabble." Science must now be content to be professional, if not professorial. In the last century it was not so. Leading men of science were in touch with one another and the larger life and influenced it. It seems strange to read that in 1842 at the Athenæum "they have soirées every Monday evening, and as all the literary and scientific men in London are in the club, they must be very pleasant." In the second volume Mrs. Litchfield has given a picture of her mother which is a worthy complement to that her brother has given us of their father. Maria Edgeworth describes her “radiantly cheerful countenance, even now, debarred from all London gaieties and all gaiety but that of her Own mind by close attendance on her sick husband." And the resources of that mind fill one with admiration. Some things are told almost too sacred for publication, yet one is glad to have known them. Two letters which she wrote to her husband on religion could not be surpassed for courage and affection. Darwin wrote on the last, "God bless you." Her literary judgment was admirably sound. Of course she knew Jane Austen by heart and could give off-hand the christian name of Mr. Woodhouse, asked in an examination paper, the point being that it can be inferred though never stated. All sorts of celebrities flash through the pages, and there are plenty of thumb-nail sketches of HIS work can claim to meet a long-felt him the labour of wrestling with the extraordi arily difficult style of the original. The chapters on adsorption generally follow Freundlich, but include some recent and impor tant work on the behaviour of sols in contact with other liquid phases. A very necessary warning against identifying phenomena only superficialy similar with adsorption, and against using the latter as a facile explanation of obscure processes, is sounded repeatedly. In the concluding section the application of colloidal chemistry t the explanation of various phenomena is illus trated by a number of examples selected at random and including the unavoidable dyeing and tanning. Here, also, the author is careful not to countenance any extravagant claims on behalf ci the science, and the student will be left under the correct and stimulating impression that colloidal chemistry can show-in the words of the famous epitaph-"great achievement but still greater promise." The book is well printed and adequately illustrated, and may be unreservedly recommended to all students desirous of a sound knowledge of what is probably the most widely important, and Twant with more justice than the majority certainly the most fascinating, branch of physical GEOGRAPHY AS A SCIENCE. of publications heralded by that familiar phrase. chemistry. The Teaching of Geography. By B. C. Wallis cannot be, and should not be tempted to imagine PE It is one of the merits of the present text-book that by far its larger portion consists of a lucid and concise account of observed facts, the description of which precedes the discussion of theories advanced to explain them everywhere but in the section dealing with adsorption, where the reversal of this order is undoubtedly the only pedagogically sound procedure. The text is divided into four parts: general properties of colloids; methods of preparation; adsorption and applications of colloid chemistry. The subjects indicated by these headings are treated clearly and adequately, the instructions for experimental work being particularly satisfactory-with the exception, perhaps, of ultra-microscopy. This is a point which always presents difficulty, as a knowledge of the principles of high-power microscopy must be presumed which is by no means general. As regards theory, the reviewer has been particularly struck with the very lucid summary of von Weimarn's theory of dispersoid formation, which gives the student all that is essential, while saving ERHAPS no school subject, in recent years, has been so much discussed as that of geography. The old meaningless lists of names of places, "famous for" all kinds of curious, as well as important things, has been ruthlessly consigned to the scrap heap. Exactly what is to take its place no one has yet determined, and each expert goes his own way and proclaims his own gospel. own gospel. Geography-economical, physical, regional, historical, practical-has annexed so many other domains of learning, that the specialists differ within very wide limits, and the nor specialist teachers are overwhelmed by conflicting claims, arguments, and interests. This book, by Mr. B. C. Wallis, covers most of the questions that interest the practical teacher, and on each and all of them he has much to say that is valuable. He is a teacher himself, that is, a teacher of children; some of the people who theorise upon the subject are only teachers of adults. Mr. Wallis would have us divide our school schemes of work into three sections-descriptive in the early stages; transitional for the inter |