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narrow groove into which light rectangular frames of The procedure adopted after many trials was to measure wood, each with a spectacle lens in it, can be slipped and theum of each portrait to the nearest half-millimetre and will stand upright (Figs. 1, 4). I chiefly use lenses of 12, to write it below. Then to mount the two portraits, each 24, and 48 inches; my eye can accommodate its focus to on a separate sledge if their facial units differed, otherwise intermediate distances, but I possess others which are some- on the same. When they differed, the facial unit of the one times serviceable. Younger persons with normal eyesight about to be used for de was distinguished as 1 m, the other would want no lenses at all. The length of the box suffices was in brackets as (u'm). Next, after referring to the above for cabinet-size photos. An opera-glass reversed enables it table, to send them to their respective de for N=5, to conto be used with larger ones, the minifying power of the sider them carefully, and to note the result. Then to do opera-glasses at various short distances having been ascer- the same for N=10, and so on, until the eye became tained.
familiarised with the differences between the portraits. Mutual mistakability may occur under any one or more Finally, guided by these provisional attempts, to fix on the of the following conditions, which are to be noted, together suitable index and letter, adding such remarks as may with further remarks :
seem wanted. a a. The portraits are apparently exact copies or reduc- I became gradually more consistent in judgment, as tions on different scales.
ascertained by comparing the results on different days, but a. They appear to be portraits of the same person at have felt all along that it would conduce to trustworthiness about the same age, though differing
pose and dress.
if two or more companions worked together and criticised b. They would be mistaken for portraits of the same one another, and recorded their common verdict. person, even though they differ in sex and considerably A very brief example will suffice. Usually an entry in age, if the hair had been cut and dyed alike, and the consists of more lines followed by general remarks. dress arranged in the same way.
I will add a few words on dealing with mistakability caused through obscurity or other hindrances to clear vision. I prepared test cards, each containing numerals printed in different types, and, having ascertained by experiment the value of de for each kind of type when just able to read it in a clear light, wrote that value boldly by its side. An appropriate test card was put by the side of the portraits, and at the time when the portraits themselves were just mistakable, the written de of that row of figures which were just unreadable, was noted. The value of de remains constant whatever be the character or amount of the optical hindrance. If the hindrance increases, the portraits and the accompanying test card must be brought nearer to the eye. They will increase simultaneously in legibility. The written de will always show what the do would be in a clear light.
The applications of the process are numerous, as must always be the case when a hitherto vague perception is brought within the grip of numerical precision. To myself it has the especial interest of enabling the departure of individual features from a standard type to be expressed numerically. The departure may be from a composite of their race, or from a particular individual. The shortcomings of a pedigree animal from a highly distinguished ancestor could be measured in this way. Many other examples might be given.
I must not conclude without expressing gratitude for answers to a request, published by me some time ago in NATURE, for waste photographs from amateurs and professionals. If I be allowed to mention a single name, it would be that of Mr. Norman Campbell, whose photographs have been eminently serviceable.
Models of Atoms. An interesting and instructive variant of Prof. Maver's experiment with floating magnets, which has been used so much to illustrate the structure of atoms, is to do away with the centripetal magnetic force and to arrange that its place be taken by forces arising from capillarity. This is managed as follows:-
A small circular dish is filled almost to overflowing material frequently containing a high percentage of sulphur with water the surface of which will be convex. A and phosphorus, decomposes hydrogen peroxide with single floating magnet (with its axis vertical) placed on astonishing rapidity," and that the metal becomes covered this moves to the centre; two or
more such with rust in a few minutes, is not, however, to be referred magnets placed on it form regular equilibrium figures, as to catalytic action, as Mr. Friend suggests, but is a constin the usual form of the experiment. The chief interest quence of the formation of acids by the oxidation of some of the modification arises, however, from the fact that the of the impurities present in the iron, and of the subsequent figures are not in general the same as in the ordinary electrolytic action. As Mr. Friend says, "the purer the arrangement. This is instructive, because it brings out iron the less is the action of the peroxide upon it," which clearly the necessity of knowing the exact law of force is another way of stating that the intensity of action will between the parts of an atom before it can be possible to be determined by the amount of acid formed on the surfare predict its structure.
of each particular sample of metal when in contact with The experiment is so easily tried by anyone that there the peroxide. is no need to go into great detail here; but it may be Cast iron is known to oxidise in air more readily than mentioned that with the particular dish and magnets used wrought iron, and this is probably due to the former cunby me it is possible to arrange ten in a single ring with taining impurities which on oxidation yield acids. The out any central nucleus, and that in a larger dish more rust formed on cast iron exposed to air often contains can, of course, be so arranged. These ten also form stable appreciable quantities of combined sulphur. groups as a ring of nine with one in the middle, or a The fact that cast iron is attacked by water in absence ring of eight with two in the middle. But a ring of seven of air, becoming darker in colour, whilst pure iron under with three in the middle is not possible ; if temporarily so identical conditions remains unchanged, may also be pa placed one of the three gradually moves out and joins the ferred to the production of a minute quantity of acid. To
The first arrangement in three groups occurs for this case the acid is not formed by oxidation, but it is eighteen magnets in all; these are stable when placed with probably hydrogen sulphide resulting from the interaction twelve in an outer ring, five in an intermediate ring, and of sulphides, such as silicon sulphide, contained in the a single one in the centre. ALFRED W. Porter. crude iron, with water.
GERALD T. Moony. Cniversity College, London, September 17.
Central Technical College, October 1.
Chemical and Electrical Changes induced by Light.
Remarkable Rainbow Phenomena. The issue of Nature for August 30 (p. 455) contains an MAY I be permitted, with reference to Mr. Spence's abstract of a paper read before Section A of the British observation of a remarkable rainbow, described in your Association by Sir Wm. Ramsay and Dr. J. F. Spencer issue of September 20, to direct attention to a number of on the chemical and electrical changes induced by ultra- phenomena of the same kind observed in Holland during violet light, in which the “ fatigue ” shown by certain the last ten years, and published by the Dutch Metrora surfaces is discussed. I have for some time been engaged ological Institute in Omweders, Optische Verschijnselen en in an investigation of the fatigue shown by metals for the At Fort William, also, on August 16, 1887. a phenophotoelectric effect, and have made a careful examination menon of this sort was seen, a drawing of which is to be of the rate at which the photoelectric current decays in the found in Trans. Roy. Soc. Edin. (vol. xxxiv., p. xvii. case of a zinc plate, polished or amalgamated. A large Fig. 17). Readers of NATURE will find an observation of Nernst lamp supplied with current from storage cells was a double rainbow, with drawing, similar to the oval doused to give a steady source of light. The decay immedi- scribed by Mr. Spence, made by Prof. Tait on September ately after exposure to the light was very rapid, but after II, 1874, in the issue of October 1, 1874, with a comment about twenty minutes became much slower. For a change by Maxwell upon it. taking place according to the “ compound interest law, The explanation of the phenomenon is simple, and <reits as in the case of a monomolecular chemical reaction or a to have been first given by Rubenson. The upper oi the single purely surface effect, we know that the curve can two ordinary and the two secondary bows is generated by be represented by an exponential term involving the time. rays which enter the raindrops after reflection from In the case of zinc, I find that the activity at any instant level of water situated behind the observer. It is obvious can be represented with considerable accuracy by the sum that the altitude of the ordinary rainbow being 429 -h, the of two exponential terms. It is possible to interpret this altitude of the one generated by reflection will be 42° +h. result somewhat on the lines followed by Rutherford in h being the sun's altitude; the same holds good for the explaining the decay of the excited activity of radium or secondary rainbow. The centres of all the bows lying in thorium, by supposing that a succession of changes takes the same vertical, it is clear that the two ordinary bow's place.
and the two secondaries touch each other at the horizon. Similar results have been obtained in the
of For further information see my Meteorologische Optik aluminium, and also with specimens of coloured fluor- (pp. 491 and 555).
J. M. PERNTER. spar. In the latter case the colour is attributed to the Vienna, September 28. presence of particles of reduced metal.
It is interesting to note that the longer waves of light tend to produce a change in the opposite sense, so that
Fugitive Coloration of Sodalite. the rapid decay at first observed on exposure to light may With reference to the properties of Indian sodalite shown be followed by a small increase in activity unless the long by Mr. T. H. Holland at the York meeting of the Brirish waves are absorbed by a solution of alum.
Association (September 27, p. 550), will you permit me to These experiments were carried out partly in the labor
point out that, although not generally noticed in the letto atory of Lord Blythswood, to whom my thanks are due, books, the change of colour referred to is not peculiar in and partly in the Wheatstone Laboratory of King's College. the Rajputana mineral. The first sodalite discovered had
H. S. Allex.
the same properly, and Giesecké, under date August 28, King's College, London, September 21.
1806, records the
of " pfirsichbluthenroth farbene" sodalite from Kangerdluarsuk, in Greenland,
“ welche die hohe Farbe auf frischem Bruche sogleich The Rusting of Iron.
beinahe ganz verliert." The same observation was made
independently by Allan (Thomson's “Annals of PhiloThe experiments made by Mr. J. Newton Friend, and sophy," 1813, vol. i., p. 104); but I am not aware that described by him in Nature of September 27, confirm there is any record of a recovery of the lost colour, which similar experiments previously made by me, and furnish Mr. Holland appears to have observed. further evidence that the rusting of iron is primarily a
JAS. CUBRIE result of acid attack. That cast iron, a very complex Edinburgh, October 1.
THE QUATERCENTENARY CELEBRATIONS
History, Paris; W. Einthoven, professor of physiology, OF THE UNIVERSITY OF ABERDEEN.
Leyden; Herbert Mackay Ellis, Director-General, Naval
Medical Service, London ; Arthur J. Evans, keeper of the THE
HE quatercentenary celebrations of the University Ashmolean Museum, Oxford ; Andrew Russell Forsyth,
of Aberdeen, which included the opening of the Sadlerian professor of pure mathematics, Cambridge ; Sir new buildings at Marischal College by their Majesties Archibald Geikie, secretary to Royal Society ; Arnold the King and Queen, were favoured by a week of Hague, U.S. Geological Survey, Washington ; H. J. Hamuninterrupted sunshine, which quickened everyone's burger, professor of physiology, Groningen; Edward Hjelt, pulse and gave splendour to the proceedings. There professor of chemistry, Helsingfors; Harald Höffding, prowere many remarks on the forethought of the Uni
fessor of philosophy, Copenhagen; Ferdinand Hueppe, pro
fessor of hygiene, Prague ; Howard A. Kelly, professor of versity in conferring the honorary degree of Doctor
gynæcology. Johns Hopkins
Hopkins University, Baltimore ; of Laws on the director of the Meteorological Office.
Surgeon-General Sir Alfred Keogh, K.C.B., DirectorOn the morning of Tuesday, September 25, there General, Army Medical Service; Rudolf E. Kobert, prowas a solemn service of commemoration in the chapel fessor of pharmacology, Rostock; Casimir Kostanecki, at King's College—that priceless heritage founded by professor of anatomy, Cracow; Hugo Kronecker, professor Bishop Elphinstone in 1500. In the afternoon there of physiology, Bern; Sir Francis H. Laking, Bart.,
remarkable procession through a mile of G.C.V.O., physician in ordinary to His Majesty the King crowded streets, by a circuitous route from Marischal and the Prince of Wales ; Commandatore Rodolfo Lanciani, College to the temporary Strathcona Hall
, built for professor of ancient topography, University of Rome; the celebrations by the generous Chancellor. This
Charles Rockwell Lanman, professor of Sanskrit, Harvard pageant, almost iridescent with robes of many
University ; Gustavus Mittag-Leffler, professor of mathecolours, included the University authorities and staff, cology, Berlin ; Sir Norman Lockyer, K.C.B., director of
matics, Stockholm ; Oscar Liebreich, professor of pharmathe Town Council, the delegates and guests, the honorary graduates, the general council, and students.
Solar Physics Laboratory, South Kensington ; Sir Oliver
Lodge, Kt., Principal of Birmingham University ; FriedIt was a striking spectacle, greatly appreciated by rich Loffler, professor of hygiene, Greifswald; Donald the keenly interested and courteous crowds, a quaint Macalister, president, General Medical Council: A. B. intertwining of town and gown.
Macallum, professor of physiology, Toronto; Sir John In the Strathcona Hall, the delegates from sister Macfadyean, Principal of the Royal Veterinary College, universities and learned institutions all over the world
Camden Town, London, N.W.; Lord M‘Laren, vice-presipresented congratulatory addresses, and represent fessor of botany, Úniversity of Tokyo, Japan ; His Serene
dent, Royal Society of Edinburgh ; Jinzo Matsumura, proative men made brief speeches. Thus the ViceChancellor of Oxford spoke for Britain, Principal | Wilhelm Ostwald, professor of chemistry, Leipzig ; Edmund
Highness Albert Honore Charles, Prince of Monaco ; Peterson for dominions beyond the seas, Prof. J. Owen, vice-president, Royal College of Surgeons of William White for the United States, Prof. Becquerel London ; W. M. Flinders Petrie, professor of Egyptology, for France, Prof. Deissmann for Germany, Prof. University College, London; Rev. George E. Post; proHöffding for Denmark, Prof. Einthoven for Holland, fessor of surgery in Johanite Hospital, Beirut; Sir Richard Prof. Lanciani for Italy, Prof. Scheviakoff-a Douglas Powell, Bart., K.C.V.O., president of the Royal logist--for Russia, and Prof. Matsumura-a botanist College of Physicians, London; Salomon Reinach, pro--for Japan, and there were many others. The huge fessor of archeology, Paris; Guglielmo Romiti, professor audience of 4000 showed enthusiastic interest in the of anatomy, Pisa ; Sir Henry E. Roscoe, late professor of famous men who filed past, especially in those who chemistry Owens College, Victoria University; Major are familiar to all, such as Sir Oliver Lodge, Sir
Ronald Ross, C.B., Liverpool School of Tropical Medicine : William Turner, and Sir Archibald Geikie.
Vladimir Scheviakoff, professor of zoology, St. Petersburg : The great event of Wednesday was the conferring | Dukinfield Henry Scott
, hon. keeper, jodrell Laboratory:
Jakob Schipper, professor of English philology, Vienna ; of honorary degrees on a phalanx of intellectual
Kew Gardens; William Napier Shaw, director of the giants, who came from all quarters of the world to Meteorological Office, London ; Joseph J. Thomson, Cavendo honour to, and be honoured by, the ancient Uni
dish professor of experimental physics, University of Camversity of Aberdeen. They included, as the Dean of bridge; Frederick Trendelenburg. professor of surgery, the Faculty of Laws felicitously expressed it,
University of Leipzig ; Sir William Turner, K.C.B., prin
cipal of University of Edinburgh ; Giuseppe Veronese, pro“explorers, discoverers, inventors; some who have all but fessor of analytical geometry, Padua ; Hugo de Vries, prosolved the mysteries of the natural universe or of the fessor of physiological botany, Amsterdam; J. William animal frame, others who have illuminated the even greater White professor of surgery, Pennsylvania University; depth of mind, others who have successfully grappled with J. W. van Wijhe, professor of anatomy, Groningen, controversies of history or the not less complex problems Holland : Sir John Williams, Bart., K.C.V.O., late proof national institutions and international relations ; men of fessor of midwifery, l'niversity College, London. thought and action, poets, musicians, and philosophers, great administrators, great rulers, and judges."
The proceedings concluded with a speech by the The list is too long to be quoted in extenso, but ported by the Times to have said :
Chancellor, who in the course of his address is rewe may note some of those who are especially concerned with science in the wide sense. It may be noted that a few who were expected were unavoidably ing universities and learned societies from all parts of the
“ The presence of so many distinguished men representabsent, such as. Signor Marconi, who was referred world might suggest, if this were the occasion to deal with to by the promoter as “the annihilator of time "; Dr. it at length, a comparison of the aims and objects which Dohrn, of the Naples Zoological Station; and Prof. we cherish here and the methods by which we seek their Lombroso. Among those upon whom the degree was accomplishment with those of similar institutions in other conferred were the following :
countries. Let me say, to begin with, that Scotland is
proud of her universities, their close connection with the Richard Anschutz, professor of chemistry, Bonn: Henri national life, their free and open constitution, their services Becquerel, professor of physics, Paris; Sir James Crichton- science and letters, their stimulating influence Browne. Kl., Lord Chancellor's Visitor in Lunacy; | especially of late years-on the schools of the country, and Casimir de Candolle, Geneva; Frank Wigglesworth Clarke, the manner in which, in spite of great difficulties, they chiel chemist, U.S. Geological Survey, Washington : Yves have kept before them lofty and high standards. All the Delaga, professor of zoology and comparative anatomy, countries of the world have each their own Paris; J. Deniker, librarian of the Museum of Natural national university. There are, among many others, the
type of English type, the German type, and the American ation of much of their educational activity. The reward type. We have no reason to be ashamed of the Scottish
they have is that-fully as much as we do here they find type. But while it is legitimate for us, especially at the their alumni in every walk of life, not in the learned procelebration of our 400th birthday, to plume ourselves on sessions only; and some of the most notable benefacwork done and service rendered, we must not forget that 'tions which the American universities have lately received others also have been making progress, and are even now come from men whose desire it is to connect them still passing us in the race of efficiency. Scotland is no longer
more closely with practical work. As a recent illustration the only country in the world that can justly boast that! of this spirit, let me refer to the great gift that was made its main industry is education ; and our universities have
the other day by my friend Sir William Macdonald to still, perhaps, something to learn in the way of relegating McGill University, Montreal. It consists of a college of a greater proportion of their work to the practical activities agriculture situated about ten miles outside the city, and of life. I do not speak from a merely utilitarian point of comprises, besides all the necessary buildings erected in view, and I know that it is the proper function of a
palatial style, some six hundred acres of ground. The university to foster even those studies which may be de
whole benefaction amounts to some 600,000l., and secures scribed as ends in themselves. If it were not for what
to the agricultural interests of the country that they shall universities do in cherishing abstract and theoretical learn
be developed hand in hand with those of a university which ing, some of the practical applications of that learning has already done so much for engineering and other pracresulting in the great triumphs of modern scientific activity
tical sciences." would never have been made. I know also that the universities, for example, of the New World have something
At the various festive meetings of the crowded four to learn from those of Europe in the direction of more days—the receptions at the two colleges and at the
solid attainment and a higher standard, at least in certain 'Art Gallery, the Town Council banquet, and Lord departments of study. But speaking for the moment as Strathcona's gigantic dinner-party of two thousand one who has lived for many years on the American con- four hundred guests—there was renewed opportunity tinent and has watched with close attention the growth
to realise the cosmopolitan nature of the concourse and of one of our greatest universities in Canada, I may be
the generosity of the response made to the l'niverallowed to record my conviction that universities on the other side of the Atlantic enjoy a considerable advantage sity's invitation. Among the famous men who were in the ease and readiness with which, unhampered as they
present as delegates we may note the following, are by any venerable traditions, they can adapt themselves taking them in order of the institutions repreto the practical needs of the various constituencies which
sented : they seek to serve. They found out long ago that law (1) Great Britain and Ireland :-Universities : Oxford, and medicine and theology are not the only legitimate Prof. Henry Goudy, Prof. Arthur Thomson ; Cambridge, points of academic study; and in their faculties of applied Prof. Henry Jackson, Dr. James Adam, Dr. William L. science they are training their young men to do work that Mollison ; Durham, Rev. Dr. Henry Gee (Master of l'niis most loudly called for. They have never accepted the versity College, Durham); Edinburgh, Prof. Alex. Crum view that universities must necessarily be institutions Brown, Prof. George Chrystal, Prof. James Cossar Ewan, cloistered and apart from the main current of public life Sir Thomas Richard Fraser, Dr. Thomas Smith Clouston ; and service. On the contrary, they make a training for Glasgow, Sir T. McCall Anderson, Prof. Archd. Bart, citizenship and for public usefulness the basis and found- Prof. John Cleland, Prof. John Ferguson, Prof. Samsun
Gemmell, Emeritus Prof. John G. McKendrick; Leeds, Trinity College, Cambridge; Right Hon. Sir Edward
(2) British Dominions beyond the Seas :-Canada :
(3) Other countries :-America (South): University of Ecuador, General Don Emilio M. Teran. AustriaHungary : University of Vienna and Imperial Academy of Sciences, Vienna, Prof. Jakob Schipper; University of Buda Pesth, Prof. Ignacz Goldziher; Bohemian University of Prague, Prof. Vaclav E. Mourek ; German University of Prague, Prof. Ferdinand Hueppe. Belgium : University of Brussels, Prof. Count Eugene Goblet D'Alviella. France : Institut de France, Prof. Emile Boutroux, Prof. Salomon Reinach. Germany : University of Berlin, Prof. Hans Dellbrück; University of Greifswald, Prof. Friedrich Löffler. Italy : Cniversity of Padua, Prof. Giuseppe Veronese. Norway : L'niversity of Christiania, Prof. A. Taranger. Russia : St. Petersburg, Imperial Academy of Military Medicine, Prof. Henry Turner. Sweden : l'niversity of Upsala, Prof. Henrick Schück (Rector); Stockholm, Royal Swedish Academy of Sciences, Prof. Einar Lönnberg Switzerland: University of Geneva, Prof. Charles Borgeaud : University of Bern, Prof. Hugo Kronecker ; L'niversity of Zürich, Prof. Theodor Vetter.
Among the guests of the University other than delegates there were many illustrious men of science, such as
Fig. 2.- Front of Mariscbal College Buildings, looking southward. (1) England :-Dr. T. Clifford Allbutt, regius professor of physic, University of Cambridge; Dr. Henry E. Arm- of chemistry, University College, London ; Sir Henry E. strong, professor of chemistry, Central Technical College, Roscoe, late professor of chemistry, Victoria University : London; the Right Hon. Lord Avebury, F.R.S.; Sir Major Ronald Ross, C.B., Liverpool School of Tropical Robert S. Ball, professor of astronomy and geometry,
Medicine ; Rev. Archibald H. Sayce, professor of AssyriObservatory, Cambridge; Colonel David Bruce, C.B. ; ology, University of Oxford ; Dr. George D. Thane, proDr. Wm. Burnside, professor of mathematics, Royal Naval fessor of anatomy, University College, London ; Dr. College, Greenwich ; the Lord Archbishop of Canterbury; Thomas E. Thorpe, C.B., director of Government LaborProf. W. Watson Cheyne, professor of surgery, King's atories, London ; Dr. J. A. Voelcker, chemist to Royal College, London ; Sir William Crookes ; Sir Edward Elgar ; Agricultural Society of England. Dr. Herbert Mackay Ellis, Director-General, Naval (2) Scotland :-William S. Bruce, leader of the Scottish Medical Service ; Dr. Arthur J. Evans, keeper of the Ash- Antarctic Expedition (1902-4), Edinburgh; Sir Henry molean Museum, Oxford ; Sir John Evans, K.C.B. ; Prof. (raik, K.C.B.; the Right Hon. the Earl of Elgin, K.G., A. R. Forsyth, Sadlerian professor of pure mathematics, G.C.S.I., LL.D., D.C.L.; Right Hon. Richard Burdor