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problem requiring solution may give a fellowship to provide the salary of a researcher selected to carry out the investigation desired, the institute supplying every facility for the work. At present twenty-three fellowships are in operation and forty research chemists are at work. At the opening ceremony fifteen honorary degrees were conferred on distinguished Americans. Though the institute possesses its own endowment and has its own board of trustees, it is an integral part of the University of Pittsburgh.

SOCIETIES AND ACADEMIES.

LONDON.

Zoological Society, March 23.-Mr. R. H. Burne, vice-president, in the chair.-R. Lydekker: The true coracoid. The element in birds and post-Triassic reptiles universally known as the coracoid is the homologue of the human coracoid process, and its equivalent the true coracoid of the monotremes and mammallike reptiles. Dr. F. E. Beddard: Certain points in the anatomy of the Cestode genera Amabilia and Dasyurotænia.-B. F. Cummings: New species of Polyplax (Anoplura) from Egypt. This paper contained a systematic description of two new species of louse based on a large supply of material in spirit collected on Acomys cahirinus, Des., and forwarded by the Department of Public Health in Egypt to the Lister Institute, by whom they were subsequently presented to the British Museum. Both the new species were fortunately collected in large numbers in all stages of development, and an account of the larvæ consequently has been prepared.-J. T. Cunningham: The resemblance in form and markings of the plates of paraffin-wax originally obtained by Prof. Kappers, of Amsterdam, to the shells of Molluscs. Examples of these structures had been exhibited at a previous meeting by Mr. R. H. Burne. Mr. Cunningham found that the forms were produced by pouring molten paraffin-wax on to the surface of cold water, and he had no doubt that Prof. Kappers's specimens were produced in the same way by the molten wax running over on to a vessel filled with water. The author concluded that the form and markings were not in either case in any way due to effects of crystallisation as Prof. Kappers supposed.

Geological Society, March 24.-Dr. A. Smith Woodward, president, in the chair.-P. G. H. Boswell: The stratigraphy and petrology of the Lower Eocene deposits of the north-eastern part of the London basin. The following divisions of the Lower Eocene occur in the area :-London Clay-basement-bed only; the Pebble-Beds and accompanying sands; Reading Beds; Thanet Beds. The unconformity of the Eocene upon the Chalk is discussed, and reasons are given for regarding the layer of green-coated flints at the bottom of the Thanet Beds in the area as a true basal conglomerate. Evidence is adduced to show that the London Clay overlaps the Lower London Tertiaries, and rests directly upon the Chalk in Norfolk. The Reading Beds also overlap the Thanet Beds in the western part of the area. A hypsometrical map of the Chalk-surface in the London Basin is presented, and a minimum estimate of the unconformity, in terms of thickness of Chalk removed, is given for the northern part of the basin. Stratigraphical details of the various divisions and descriptions of new sections are given. The variations in lithology of the Reading Beds are described, and it is shown that the PebbleBeds belong lithologically and petrologically to the Reading Beds, but that their scanty fauna is a London Clay one. The distribution of the sarsens in the area is plotted out on a map, and their petrology is con

sidered; it is concluded that, in this district, they are derived from the sands of the Reading Beds. The mineral constitution of the various divisions of the Eocene Beds is discussed in detail.

MANCHESTER.

Literary and Philosophical Society, March 9.-Mr. F. Nicholson, president, in the chair.-Sir Ernest Rutherford: Origin of the spectra given by ẞ and y rays of radium. An account of recent experiments by Sir Ernest Rutherford and Dr. Andrade to determine the wave-length of the very penetrating y rays emitted from radium. The spectrum of the y rays was obtained by a photographic method by reflecting the rays from a thin slip of rock-salt. The radioactive source consisted of a fine glass tube containing a large quantity of radium emanation. Special precautions were taken to get rid of the effect of the Brays emitted with the y rays. A large number of lines were observed in the spectrum over a wide range of wave-length. Two well-marked lines are reflected from rock-salt at 10° and 12°, and correspond to some soft y rays. There were other strong lines of 1° and 1.70, corresponding to the very penetrating rays. The shortest wave-length observed was 0.7 angström unit, which is about 1/50,000 of the wave-length of visible light. This radiation has much the shortest wavelength at present known. An account was also given of the methods for determining the magnetic spectrum of the ẞ rays. The rays from a fine source, passing normally in a strong magnetic field, describe a circular path and fall on a photographic plate. A number of well-marked lines are observed on the plate, which correspond to groups of rays of definite velocity. The speed and energy of the ẞ particle comprising each of those groups of rays from radium products have been accurately determined by Rutherford and Robinson. The general evidence indicates a very close connection between the emission of ẞ and y rays from radio-active bodies, and that the energy of the groups of rays are intimately related with the frequency of the y radiation from which they arise. The author outlined a general theory to explain the connection between the ẞ and y rays.

PARIS.

In

Academy of Sciences, March 29.-M. Ed. Perrier in the chair.-Edmond Delorme: Artificial limbs for the use of the amputated. Medical treatment is required by the amputated for some time after the wound has healed, if the full benefit of artificial limbs is to be obtained.-J. Comas Solá: Certain rapid displacements of short duration registered by photography. photographs of the sky taken for the purpose of detecting minor planets, a certain number of stars showed changes of position from hour to hour, which could not be attributed to contractions or deformations of the gelatine of the plate.-J. Comas Solá: The discovery of a new minor planet.-E. Keraval : A family of triply orthogonal systems.-Gaetano Scorza: Singular Abelian functions.-M. Dussaud: New experiments on sources of light of small surface.-O. Bailly: The constitution of glycerophosphoric acid and of lecithin. Egg lecithin is a mixture of two isomers from which a mixture of a- and B-glycerophosphoric acids is obtained, the latter predominating.-G. Tizzoni: The infectious nature of pellagra. Results of researches made in Italy and in Bessarabia. Further studies on the micro-organism previously described by the author under the name of Streptobacillus pellagrae.-M. Guépin: The destruction by suppuration and ablation of a considerable part of the brain resulting in no appreciable trouble.-Pierre Delbet: Extra-pericardic cardio-thoracic symphysis.-H. Busquet: The compara

tive pharmacodynamical action of gold in the colloidal and soluble states. So far as gold is concerned, the qualitative reactions on the heart are quite different in the colloidal and dissolved conditions.-B. Collin : Chromidina elegans.-E. Kayser: Contributions to the study of the ferments of rum.

BOOKS RECEIVED.

Descriptive Geometry for Students in Engineering Science and Architecture. By Prof. H. F. Armstrong. Pp. vi+ 125. (New York: J. Wiley and Sons, Inc.; London: Chapman and Hall, Ltd.) 8s. 6d. net.

Structural Steel Drafting and Elementary Design. By C. D. Conklin, Jun. Pp. vii+ 154. (New York: J. Wiley and Sons, Inc.; London: Chapman and Hall, Ltd.) 10s. 6d. net.

Canada. Department of Mines. Mines Branch. Economic Minerals and Mining Industries of Canada. Pp. vii+78. The Physical Properties of the Metal Cobalt. Part ii. By Dr. H. T. Kalmus and C. Harper. Pp. vi+48. Report on the Building and Ornamental Stones of Canada. Vol. iii. Province of

Quebec. By Dr. W. A. Parks. Pp. xiv + 304. (Ottawa: Government Printing Bureau.)

Royal Botanic Gardens, Kew. Bulletin of Miscellaneous Information, 1914. Pp. 404+ Appendix. (London: H.M.S.O.; Wyman and Sons, Ltd.) 4s. 6d.

Smithsonian Institution. U.S. National Museum. Report on the Progress and Condition of the U.S. National Museum for the Year ending June 30, 1914. Pp. 252. (Washington: Government Printing Office.) Smithsonian Institution. U.S. National Museum. Bulletin 89: Osteology of the Armored Dinosauria in the U.S. National Museum, with special reference to the genus Stegosaurus. By C. W. Gilmore. Pp. xi+143. (Washington: Government Printing Office.) A Chaplet of Herbs. By F. Hine. Pp. xv+168. (London: G. Routledge and Sons, Ltd.) 2s. 6d. net. The Potamogetons (Pond Weeds) of the British Isles, with Descriptions of all the Species, Varieties, and Hybrids. By A. Fryer and A. Bennett. Pp. x+94 +60 plates. (London: L. Reeve and Co., Ltd.) 5 guineas net.

Floral Rambles in Highways and Byways. By Rev. Prof. G. Henslow. Pp. v+294. (London: S.P.C.K.) 6s. net.

University of Pennsylvania. The University Museum Anthropological Publications. Vol. vi., No. 2: The Dance Festivals of the Alaskan Eskimo. By E. W. Hawkes. Pp. 41. (Philadelphia: University Museum.)

Annual Report of the Board of Regents of the Smithsonian Institution, 1913. Pp. xi+804. (Washington Government Printing Office.) : 1.10 dollars. The Evolution of Sex in Plants. By J. M. Coulter. Pp. ix + 140. (Chicago: University of Chicago Press; Cambridge: At the University Press.) A Campaign against Consumption. Ransome. Pp. viii+263. versity Press.) 10s. 6d. net.

4s. net.

MONDAY, APRIL 12,

ARISTOTELIAN SOCIETY, at 8.-Phenominalism: C. D. Broad. VICTORIA INSTITUTE, at 4.30.-Astronomical Allusions in Sacred Books of the East: Mrs. Walter Maunder.

SOCIETY OF CHEMICAL INDUSTRY, at 8.-The Detection of small quantities of Paraffin Wax in Beeswax, and the Determination of a new constant for East Indian and European Beeswaxes: M. S. Salamon and W. A Seaber.-The Action of Dilute Acid, Alkalies and Salts on certain Metals: A. J. Hale and H. S. Foster.-Method of Assaying Copper: Arthur Fraser.-Resumed discussion of Dr. Tripp's Paper on "Dickson Centrifuge System of Sewage Disposal."

TUESDAY, APRIL 13.

SOCIETY OF ENGINEERS, at 7.30.-Main Roads, Past and Present, and Modern Methods of Construction and Maintenance: F. Grove. ZOOLOGICAL SOCIETY, at 5.30. - A List of the Snakes of the Belgian and Portuguese Congo, Northern Rhodesia, and Angola: G. A. Boulenger. (1) Some new Carnivorous Therapsids in the Collection of the British Museum (2) The Organ of Jacobson and its relations in the "Insectivora": Dr. R. Broom.-A Note on the Urostyle (Os Coccygeum) of the Anurous Amphibia: Dr. G. E. Nicholls.-Some Notes on the Nato Breed of Cattle (Bos taurus): E. Gibson.

INSTITUTION OF CIVIL ENGINEERS, at 8.-Impact Coefficients for Railway Girders: C. W. Anderson.

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By Dr. A. Books Received (Cambridge: At the UniDiary of Societies

DIARY OF SOCIETIES.

FRIDAY, APRIL 9.

ROVAL ASTRONOMICAL SOCIETY, at 5.-(1) A Correction to the Determina tion of the Constants of the Node, the Inclination, the Earth's Ellipticity. and the Obliquity of the Ecliptic; (2) The Elements of the Moon's Orbit: E. W. Brown. The Errors of Measurements on Astrophotographic Plates Winifred Gibson.-The Rotation of the Earth: Hermann Glauert. -A Simple Geometrical Construction for Determining the Heliographic Co-ordinates of Sun-spots: F. Henrotean.-Probable Papers: Com. parison of Magnitude Scales. Sixth Note-The Oxford Magnitudes, With a Preliminary Discussion of the Existence of Obscured Patches in the Sky: H. H. Turner.-The Sun-spot and the Solar Corona of 1914, August 21: A. L. Cortie.

ALCHEMICAL SOCIETY, at 7.30.-The Phallic Element in Alchemical Doctrine: H. Stanley Redgrove.

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, APRIL 15, 1915.

COLOUR VISION.

An Introduction to the Study of Colour Vision. By Dr. J. H. Parsons. Pp. viii+ 308. (Cambridge: At the University Press, 1915.) Price 12s. 6d. net.

THE

HE whole subject of colour vision is admittedly very difficult, as the knowledge of it involves familiarity with the experimental results of a physical as well as of a physiological laboratory, with the minute anatomy of the retina, and with the latest results of psychological research. Hitherto, all that is known, and the various suppositions that have been made about

photometer. The curious coloured phenomena of rapid, intermittent stimulation of the retina (e.g. Benham's top) lead us to expect that there would be a marked discrepancy. However, the author's statements are fully borne out by Ives's results with the flicker photometer.

On p. 3 a sentence that refers to the diffraction spectrum has missed correction when the proofs were read:

that the spectrum is less bright and less extended "It suffers, however, from the disadvantage than the prismatic spectrum, and from the still greater objection that the interference spectrum is never free from scattered light."

Surely the extent of the spectrum depends en

the subject, could only be learnt by a prolonged tirely upon the fineness of the grating, and its

search through innumerable scattered papers on physics, physiology, medicine, and psychology in various languages, chiefly English and German; so that it is with most cordial thanks to the author that this résumé of the subject in its present state is welcomed.

The book is divided into three parts: part i. (pp. 1-157) devoted to "The Chief Facts of Normal Colour Vision"; part ii. (pp. 158-192), "The Chief Facts of Colour Blindness"; and part iii. "The Chief Theories of Colour Vision." The arrangement is admirable, the facts are well described with very few omissions, and no one after reading the first 191 pages will be surprised that so far no theory has been suggested that will account for all the facts. Perhaps a few of the difficulties of the subject may be indicated.

A given colour may be determined as is well known by its hue, its luminosity, and by its degree of saturation. It is not always remembered that :

"Great increase of intensity of light not only alters its hue, but also alters its saturation, so that eventually it produces only the sensation of white. light. It would seem, therefore, that luminosity is in some recondite sense an inherent whiteness' in the colour itself, differing in degrees in different spectral colours and varying with the intensity of these colours. Clearly we are here at the outset face to face with a physiological fact of immense importance, and much of the difficulty of colour vision is connected with this fact" (p. 29).

There is the obvious difficulty in comparing the luminosity of two different coloured lights, arising from the fact that they give rise to two different impressions, and we are surprised to find that, according to the note in the preface, there is no discrepancy when the luminosity is measured by the equality of brightness method or by the flicker

brightness may be increased by increasing the size of the grating; and if by the term "interference spectrum " is meant a diffraction spectrum, any impurity in it is due to the faultiness of the grating.

We are glad to notice Mr. Parsons's criticism of v. Helmholtz's spectro-photometer and similar instruments in which the intensity of light is reduced by means of Nicol prisms; much of the German work on the subject is inaccurate owing to the polarising methods used.

With regard to Weber's law, the important point mentioned on p. 20 that "it does not hold good for very low or very high intensities of stimuli" is to be borne in mind. Fechner's law is true within the limits that Weber's law holds. Schirmer found that it was true between 1 and 1000 candle-power illuminations (i.e. the function is continuous between these limits), but that at first his minimum difference was, while after eight days' practice he could recognise a change of or even less (see Ophth. Rev., vol. x., p. 179). Possibly the failure of the law at the lower limit might be explained by Fechner's later addition of a term so to represent the "intrinsic light of the retina." If E denote the sensation, and S the stimulus, Fechner's law

then takes the form

E=C log(S+50) + C'

where C and C' are constants. Mr. Parsons makes no reference to this suggested emendation. The failure of the law at the upper limit may be due to changes in the mechanism verging on the pathological. The variation of the minimum distinguishable difference not only in each individual, but also according to his practice (as in the case of Schirmer), necessitates great precautions being used in the application of Fechner's law.

When the eye has been kept in the dark for

twenty minutes or so, the condition of scotopia or twilight vision is developed, in which the retinal sensibility is enormously increased; it will now be found that if the illumination be very low the eye is absolutely colour blind. The curve of luminosity in such an achromatic scotopic eye is is practically identical with the luminosity curve of the spectrum in any colour-blind person (p. 53), the brightest part of the spectrum being near the E line (530 μu) instead of near the D line (580 μμ) as in the normal eye.

The phenomena of simultaneous and successive contrast and fatigue are dealt with in pp. 100-129, and then there follows an interesting account of the researches on the discrimination of colour

by various animals and by primitive races. Conclusions about both of these must necessarily be indefinite. With regard to the latter, the mural decorations of ancient Egypt show that the sense of colour for red, yellow, green, and blue was well developed five or six thousand years ago.

Limits of space forbid a review of Part iii. on the various theories of colour vision: the duplicity theory that the cones are the seat of impulses that lead to colour perception, while the rods are only influenced by light stimuli; the three components theory (Young, Helmholtz); the three opponents theory (Hering); and seven other theories are described and criticised with justice and judgment. The author is to be congratulated on producing a work that contains an immense amount of information with a good bibliography on the subject. He has given us an excellent general and unbiassed view of the facts and theories of colour vision.

THE EXPERIMENTAL METHOD IN MEDICINE AND SURGERY. Animal Experimentation and Medical Progress. By Prof. W. W. Keen. With an introduction by Dr. Charles W. Eliot. Pp. xxvi+312. (Boston and New York: Houghton Mifflin Company, 1914.) Price 7s. 6d. net.

IN

N America there are very few surgeons more eminent, more beneficent, or more widely beloved than Prof. Keen. He fulfils and represents the very highest traditions of American surgery. He has done great things in practice, and in teaching, and in writing; and his name is held in reverence by doctors and surgeons over here. So, when he writes a book for general reading on a medical subject, the general reader had better read it: especially as it has an introduction from Dr. Charles W. Eliot, sometime president of Harvard University. Besides, the book is admirably written, full of learning, full

of sympathy, full of a thousand facts touching man's daily welfare.

It is a justification, and more than justification, of experiments on animals for the advancement of the science and art of medicine and surgery. Prof. Keen is one of those leaders of his profession who are very sensitive to the brutal abuse and

false witness of the "anti-vivisectionists."

Whether it is wise to care so much what they say, each man must settle for himself. Anyhow, Prof. Keen does care very much indeed. He takes it to heart that these wild people are set to insult the medical profession, to give the lie to plain facts, and to attack with virulent language the very methods which they themselves take advantage of when they are ill. These people seem to be just as unkind and untruthful in America as they are here. Indeed, we are having a rest from them here, since the war began; except that some of them are trying to stop our soldiers from being protected against typhoid fever. It will be a grand thing, after the war, if we can keep antivivisection down, and give ourselves to worthier pursuits.

The book is a collection of essays, from 1885 to 1913, on the debt which mankind and the animal world owe to experiments on animals; and on the character and the attitude of anti-vivisec

tion. The essays are complete, final, authoritative; they are the work of a master of surgery, a leader among surgeons. Where all are good it

is hard to prefer one before another. Among those essays which review the benefits gained from experiments on animals, nothing could be better than "Recent Progress in Surgery," "Vivisection and Brain-Surgery," and "What Vivisection has done for Humanity." Among those essays which review the moral obliquity of antivivisection, nothing could be better than "The Influence of Anti-vivisection on Character," and "The Anti-vivisection Exhibition in Philadelphia in 1914." These two essays are masterpieces; they are gentle, quiet, courteous; but they expose a state of mind, in some American women, which is not pleasant to contemplate. Things were bad enough here, up to last August; but they seem even worse in New York.

Indeed, that is one of the strongest arguments against anti-vivisection-that it tends, unless it be held under self-control, to such amazing dishonesty, such greedy willingness to believe evil of other men, such loss of the sense of responsibility and of restraint.

But these faults, after all, are not the main theme of the book: and the work of nailing lies to counters is less important to us than the work of setting forth the great discoveries of medical and

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(1) IT

T cannot have been an easy task to prepare the new edition of Salmon's classical treatise; the result may be considered quite satisfactory, although, no doubt, different readers will form different opinions about the choice of additions that has been made. In this volume, the principal ones are as follows:-First of all, a considerable addition has been made to the section on line-geometry. So far as we can judge, this has been very well done; it includes Ribaucour's theory of isotropic congruences, a good deal about normal congruences, and other interesting matter. Next, and partly connected with the foregoing, we have an account of curvilinear co-ordinates, triply orthogonal systems, and cyclides; also other theorems due to Ribaucour.

In the part dealing with cubic and quartic surfaces, there is a sketch of Segre's analysis of the singularities of cubics; Geiser's correspondence of lines on a cubic with bitangents of a plane quartic; and some very good articles on cyclides, and the special quartics of Steiner and Kummer. Towards the end of the book, we have eight pages or so on birational transformations, with some useful references, and a revised table of singularities, mainly based on Zeuthen's memoir of 1876 (Math. Ann., x.). This last does not seem to be quite up to date; for instance, no reference has been made to the work of Enriques and Castelnuovo, and their discussion of the deficiency of a surface, which has yielded a new fundamental characteristic, besides that called the deficiency in this book.

Reference is made (Art. 527a) to some recent work on the reduction of a cubic to the canonical

5

form x = 0, and the proof that this is unique.

=

1

One way of doing this is to obtain the equation II.x; o, by a combination of invariants and covariants; this the present writer succeeded in doing a good while ago, with the help of Salmon's list of invariants, but the result was unpleasantly long.

Perhaps the most striking omission in the revised work is that of the theory of minimal surfaces. It would not have taken very many pages to give a fair account of this elegant theory, now that Lie and Weierstrass have reduced it to

its simplest form. However, it may fairly be said that a student who has this work, and Prof. Forsyth's "Differential Geometry," will be able to make acquaintance with all the most important divisions of the subject, and be able to follow up any one in which he is specially interested.

(2) It is gratifying to see that Mr. Hardy's excellent treatise has so soon reached a second edition; and it helps to justify the statement in the preface that "it is no longer necessary to apologise for treating mathematical analysis as a serious subject worthy of study for its own sake." The author combines, in a remarkable way, strictness of method with an agreeable style; and his choice of topics seem to us to be eminently judicious. eminently judicious. The principal additions in this re-issue are an account of Dedekind's theory of irrational numbers; a proof of Weierstrass's theorem about points of condensation, of the Heine-Borel theorem, and of Heine's theorem about uniform convergence; the notions of "limits of indetermination" and "implicit function are also discussed. To save space, some analytical geometry and trigonometry has been deleted. The examples are well chosen, and hints towards solution are frequently given. This book, and Mr. Bromwich's "Infinite Series," to which Mr. Hardy refers in his preface, ought to do a great deal towards making school and college mathematics more rigorous, without making it repulsive; on the contrary, the apparent paradoxes explained, and the latent fallacies exposed, ought to provide a certain amount of fun, even for an undergraduate.

There are one or two very trifling points that

may be noticed. On page 231, D-1(x-1), when x is negative, is defined as log(-x). This is very artificial, especially as the figure, page 359, implies that logx is undefined when x is negative. The same complaint of artificiality applies to the treatment of differentials (page 280). A rather more important point is on the proof (page 313) that the sum of a series of positive terms is the same "in whatever order the terms are taken."

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