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the corpuscular radiation is small. For a slightly more penetrating primary beam a rapid increase in the intensity of both the secondary Röntgen radiation and the corpuscular radiation takes place. This seems to suggest that the production of corpuscular radiation is in some way intimately associated with the emission of the Röntgen type of radiation.

(2) I had recently shown that when homogeneous radiation falls upon a thin layer of a substance which may act as a secondary radiator, a portion is transmitted unchanged, and that the fraction of the remaining energy which is transformed into secondary Röntgen radiation decreases as the primary beam becomes more penetrating. In the present experiments it is found that the corresponding fraction of the remaining energy which is transformed into corpuscular radiation increases as the primary beam becomes more penetrating.

(3) The corpuscular radiation emitted by these metals when subjected to homogeneous beams is itself surprisingly homogeneous, whether the exciting beams are "soft" or very hard."

(4) The absorption coefficients of the corpuscular radiation from a given metal excited by homogeneous secondary Röntgen radiation vary with the nature of the exciting radiation. These absorption coefficients are a decreasing linear function of the atomic weight of the secondary radiator.

I hope to publish further details of these experiments shortly. CHARLES A. SADLER.

George Holt Physics Laboratory,
Liverpool University.

Drought in South-west Ireland.

THE deficiency of rainfall in the south of Ireland, to which Mr. Armstrong refers in NATURE of October 21 (p. 487), has been apparent in the annual total rainfall for the last three years, the deficiency also affecting the southwest of England. At the same time, there has been a marked excess of rainfall in the north of Ireland, deficiency and excess being taken as synonymous with quantities below and above the average of many years. It is frequently found that parts of the country, often quite narrow strips, show a marked deficiency of rainfall for several successive years, and afterwards revert to an average condition or show an excess. The most probable explanation seems to me to be a change, perhaps a slight one, in the prevailing tracks of the centres of barometric minima, but I have not found data in a form suitable for testing the truth of the suggestion.

The extreme dryness of August was experienced over a large area of the south of Ireland, less than half an inch of rain having fallen over about 2800 square miles. In September less than half an inch fell over not more than 500 square miles.

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I may perhaps be excused for pointing out that while Mr. Armstrong uses "absolute drought to describe a period of twenty-four hours without rain, it has been usual for many years to reserve the words "absolute drought for a period of more than fourteen consecutive days without recorded rainfall. HUGH ROBERT MILL.

62 Camden Square, London, N.W., October 25.

Derivation of the Word "Theodolite." ALTHOUGH the etymology of the word theodolite has been discussed from time to time,' no satisfactory solution has hitherto been established. It was first used in England, and the earliest reference to it is contained in a book by Leonard Digges (completed and published by his son, Thomas) called "Geometrical practical treatize, named Pantometria, diuided into three bookes, longimetria, planimetria, and stereometria, &c.," first pub

1 Philosophical Magazine, vol. xxviii. (1846), note by de Morgan, po. 287-9. Poggendorff's Annalen, vol. cxxxiii. (1868), pp. 192. 349. Zeitschrift für Vermessungswesen (1880), p. 55: (1883), p. 321; (1908), pp. 81-91 and 113-25. Vogler's Praktische Geometrie (1885), d. 361. Proc. Inst. C.E., vol. clxxiii. (1907-8), p. 339. Preussische Jahrbücher, note by Prof. Didolff, vol. cxvi. 1904), pp. 362–4.

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sightes,' and the circle was 2 feet in diameter, and fastened in the top of some staffe." He does not state how the name was derived, and spells it "theodelitus and "theodolitus" alternately. William Bourne ("Treasure for Travailers," 1578) named the same instrument "horizontall or flatte sphere," and not theodelitus; but when he speaks of the alidade he calls it only once alideday, but otherwise always athelida. After this de Morgan, who first discussed the derivation in the Philosophical Magazine, concluded that the theodelited circle " of Digges, who, however, does not use that adjective, and athelidated circle " of Bourne, were various corruptions of the Arabic word al-idhâda (a sort of rule), from which the word alidade, which carries the sights or telescope of a theodolite, is derived.

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It has been suggested by various writers that theodolite is derived from the Greek roots Béa (sight), dós (the way), and Aleos (a stone), for the latter root Airós (smooth) being

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In searching for a more satisfactory solution, the idea occurred to the writer that the word would naturally be compounded to represent the principal parts of the instrument, and when reading Prof. E. Hammer's latest and most interesting discussion in the Zeitschrift für Vermessungswesen, vol. xxxvii. (1908), pp. 81-91 and 113-25, he was impressed by one of the illustrations reproduced of Digges' theodolitus" and description of it, with special mention of the words sightes, index, and "double scale." He would the true submit, therefore, that etymology is from the Greek words 0a=a sight; odeλós= any pointed instrument; s=a circle or a felloe of a wheel. These Greek words appear to be those which would actually denote the three essential parts of the instrument, viz. the sight, the index arm, or alidade (Digges uses the word index, never alidade), which is represented as a pointed instrument, and the limb of graduated circle. The spaces on the circle appear like the

be admitted that Higgins, who stated these facts and reasoned very justly upon them in his "Comparative View of the Phlogistic and Anti-phlogistic Hypotheses" (1789), did not give any sign, by collating them, that he felt himself on the threshold of a great discovery. Again, Gay-Lussac and Humboldt, taking up the study, for purposes of eudiometry, of the combination of hydrogen and oxygen, found the ratio between these gases to be 2 : 1 as nearly as they could measure. This was in 1804. The observation arrested Gay-Lussac's attention. Curious to find if other suchlike cases exist, he began work which resulted in the discovery of his law, one of the most important in science.

Gay-Lussac, like Newton, did not form hypotheses. The memoir in which he set forth his work is remarkably free from speculative matter. His conviction was that "in natural science, and above all in chemistry, generalisation should come after and not before a minute knowledge of each fact." And assuredly the history of Gay-Lussac's law in science does show that a "law of nature may prove a dangerous weapon to the man who puts it to theoretical and practical uses, before its range and bearings in nature have been accurately fixed.

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The law when published aroused the widest interest. The world of science was just then pondering the atomic theory in the form impressed on it by Dalton, and it was obvious that theory and law must stand in the most intimate relation to one another. Strangely enough, the law was objected to by Dalton of all people, and by him alone. In the second part of his "New System of Chemical Philosophy," published in 1810, he made strictures on it, and concluded:-"The truth is, I believe, that gases do not unite in equal or exact measures in any one instance; when they appear to do so, it is owing to the inaccuracy of our experiments. In no case, perhaps, is there a nearer approach to mathematical exactness, than in that of one measure of oxygen to two of hydrogen; but here the most exact experiments I have ever made gave 197 hydrogen to I oxygen." Berzelius wrote Dalton protesting in the most courteous way against the part of the atomic theory "which obliges you to declare as inaccurate the experiments of Gay-Lussac, on the volumes in which gases combine. I should have thought rather that these experiments were the finest proof of the probability of the theory; and I confess to you, that I will not so readily think GayLussac at fault, especially where the point is one of good or of bad measurement." Nothing, however, could ever remove the distrust Dalton felt in the law. The chemists who accepted both Dalton's theory and Gay-Lussac's law had themselves to solve the problem of defining the relation between the two. No more than Dalton would Gay-Lussac do anything to help them. Even so late as the year 1814, in his memoir on iodine, and in the one on prussic acid of the following year, he ignores the atomic theory. He uses the word "molecule " for the sake of convenience, and that is all. Yet there must be a connection between the specific gravities, that is, the weights of equal volumes, of different gases and their atomic weights. This connection is the primary subject of a paper by Prout, published in 1815. Here he advanced his famous hypothesis that the atomic weights of the elements are multiples of the atomic weight of hydrogen, but there is good reason to think that the hypothesis was conceived after the data had been rounded off.

Berzelius had already, in 1813, if not earlier, given his solution of the problem. This was his "volumetheory," that equal volumes of different gases contain the same number of atoms. This hypothesis affords

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a basis of a purely physical kind for the determination of atomic weights, for it means that the atomic weights of different gases stand in the same ratio to one another as the weights of equal volumes of the gases.

The "volume-theory," plausible as it seems, involved its author in difficulties one after another, which finally became overwhelming. Or arises as soon as the theory is formulated. Each atom of hydrogen, on combining with chlorine, could, as Berzelius and Dalton understood the atom, yield only one compound atom of hydrochloric acid. But the volume of the hydrogen is half that of the hydrochloric acid which it produces, so that the atom of the element occupies only half the volume of the compound atom. Hence the theory must either be limited to elements. or given up altogether. Years before Dalton had to face the same difficulty in the case of nitric oxide. What he did at first was to abandon outright the hypothesis that atoms of different gases have the same volume, and then to object even to Gay-Lussac's law. Dalton was "for thorough." What Berzelius did was to make the "volumetheory" apply only to the elements.

In course of time another difficulty appeared. The atoms of many important elements seemed to enter into combination only by pairs. This strange result arose in the following way. Berzelius began in the year 1826 to ascribe the general formula RO to all strong bases. Now, by the chemical equation for the formation of a chloride from a base-RO+H2Cl2 = RC1, + H2O—it is plain that the amount of acid needed to form a chloride with one molecule of a base contains two atoms of hydrogen and two of chlorine. That is, as Berzelius saw, the hydrogen enters into chemical combination in pairs, and so does the chlorine atom.

This, be it noted, involves a conception of the element which is precisely the reverse of the modern one. Hydrogen is now supposed to consist of physical atoms, each of which can be halved when it enters into chemical combination. The physical atom of hydrogen is composed of two chemical ones. Berzelius had formed the conception of a chemical atom composed of two physical ones. It applied to quite a large number of elements in addition to hydrogen, namely, to chlorine, fluorine, bromine, iodine, nitrogen, phosphorus, antimony, and arsenic.

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The very natural comment on this was made by Gmelin, that the "existence of the physical atom was improbable and its adoption superfluous and troublesome. One could arrive at Gmelin's system of chemical formulæ by suppressing every pair of physical atoms in Berzelius's formulæ, and putting in a chemical atom instead. Thus H,O became HO. Nobody could help seeing that Berzelius's system simply led the way to Gmelin's. This was a great blow to the "volume-theory," for Gmelin's system differs from Berzelius's only by leaving out the volume-theory" and all its consequences.

The above as an objection to the theory was perceived and felt to be overwhelming only in course of time. As already explained, from the first the theory could include in its scope only the elements. But before long Berzelius had to limit the theory still further. So long as it is applied to elements the molecules of which are of the same degree of complexity, hydrogen and oxygen, for instance, the physical method of finding atomic weights is in agreement with the chemical. The ratio H/O,, which the former method gives, is the same as the ratio H/O given by the latter. But this is a matter of accident. About the year 1826 Dumas succeeded in finding the vapour-density of elements such as mercury and phos

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The only sound application of the law to theoretical chemistry was made by Avogadro in 1811. In considering his teaching, it is best to set aside the word atom and its associations, at least in the first place, and to use the word "molecule " instead. Avogadro's hypothesis is that equal volumes of different gases contain the same number of molecules. In that case the weights of equal volumes of gases are proportional to their molecular weights.

The hypothesis has a special and important consequence regarding the constitution of the molecule. For instance, each molecule of hydrogen, with the necessary chlorine, yields two molecules of hydrochloric acid. But each molecule of the acid contains hydrogen, and therefore the hydrogen molecule has certainly been halved. This conception of the molecule of an element as a thing which may consist of parts is an inevitable consequence of Avogadro's hypothesis, and it was boldly accepted by him. The mere possibility of such a thing was scouted by Thomson, and Berzelius, and Graham as utterly subversive of the atomic theory. Yet it forced itself forward again and again upon Ampère, Dumas, Prout, Waterston, Krönig, Gerhardt, Laurent, Clausius. Finally, in 1860, Cannizzaro was able to convert chemists to Avogadro's hypothesis and all its consequences. Since then the hypothesis, based as it is upon Gay-Lussac's law, has been the fundamental doctrine of chemistry.

One thing about the definition of the law is worth noting. Nothing is said in it, but much is implied, regarding the conditions under which the gases are measured. The teacher would do well to direct attention to this. There is the obvious assumption that the different gases concerned in a particular experiment are measured under the same temperature and

the year 1819, in conjunction with Dulong, he determined the atomic weight of carbon by the physical method. The process adopted was to weigh a certain bulk of carbon dioxide and subtract the weight of the same bulk of oxygen. The difference is the weight of the carbon, on the incorrect assumption that carbon dioxide contains exactly its own bulk of oxygen. The atomic weight was found to be 76'44 (O=100) or 12'23 (O=16). This datum, which as a matter of fact is much too high, was long used in chemistry. Berzelius should not have fallen into this error, for he had received a warning two years before against the danger of the physical method. He had determined the atomic weight of sulphur by an experiment, similar to the carbon dioxide one, with sulphur dioxide, and he set aside the result, which was 103'35 (O= 100), because it differed so much from the figure, 100'7, which he had obtained by a chemical method.

Dumas and Stas found it necessary, in the year 1839, to embark on a re-investigation of the atomic weight of carbon. Dumas had been analysing the hydrocarbon naphthalene, and had obtained the anomalous result, again and again, that the percentages of carbon and hydrogen added up to much more than 100. As a result, the atomic weight of carbon was found to be 75'00, instead of 76'44, as Berzelius had said.

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This was a severe blow to Berzelius. He had endured many reverses. One cherished conviction of his had gone after another. Chlorine and nitrogen had proved to be elements and not compounds of Oxygen, the volume-theory" had become untenable, his electrochemical theory was undermined, and his system of chemistry was threatened by Gmelin. Berzelius was yet the great master of atomic-weight determination. Even that satisfaction was now denied him; none of his atomic weights was to be above suspicion any longer, all because he had made an unjustified use of Gay-Lussac's law, twenty years before. There is a strange irony in the difficulties in which Berzelius involved himself time and again by his use of this law, in view of the protest he had made against Dalton's refusal to accept it. A. N. MELDRUM.

ANEMOGRAPHIC OBSERVATIONS IN INDIA.1

pressure. But the definition implies another assump- MOST of these memoirs are by the late Sir John

tion, namely, that different gases behave in the same way under the same conditions. Otherwise the combining ratio, say, of hydrogen and chlorine, could not remain constant over a range of temperature and

pressure.

Of course, we know that the combining ratio of two gases does not remain strictly constant when the conditions alter. The fact that a gas such as carbon dioxide deviates considerably from Boyle's law and Charles's law leads to the expectation that GayLussac's law is itself only an imperfect description of the facts. The expectation is verified, for even the combining ratio of hydrogen and oxygen is not strictly 21, but has been ascertained to be 2'00285 (Scott), 2'0037 (Leduc), and 2'0027 (Morley). This is an important consideration, for molecular and atomic weight data obtained on the assumption that GayLussac's law is strictly accurate must be defective. The physical method cannot lead to the same result as the chemical until a correction is introduced, and then the discrepancy is found to disappear. One systematic way of making this correction has been devised and used by M. Daniel Berthelot, and another by M. Guye.

Berzelius was led into a grave numerical error by his unqualified acceptance of Gay-Lussac's law. In

Eliot, whose loss, while he was still capable of much useful work, all meteorologists deplore. They deal with the changes in wind direction and force at the stations, showing both the diurnal and the seasonal variations, and form a store-house of information for anyone who wishes to study the Indian

monsoons.

Saugor Island is situated in the north-west of the Bay of Bengal on the coast, about sixty-five miles in a direct line from Calcutta, and ninety if the bends of the river are followed. The land around it is perfectly flat, and only a few feet above the sea, so that the exposure is an excellent one.

The land at Alipore is also flat, but there are many trees in the district the tops of which are level with or above the anemometer. As might be expected, the winds are far stronger at the coast station.

Saugor Island lies in the track of the circular storms (cyclones) of the Bay of Bengal, and it is of interest to compare the maximum hourly velocity in these

1 A Discussion of the Anemographic Observations recorded at Sangor Island from March, 1880, to February, 1904. Also at Alipore, Calcutta, from March, 1877, to February, 1904. Vol. xviii., part ii. Also at Pachmark from September, 1883, to April, 1887. Also at Nagpur from January, 1882, to December, 1902. Vol. xix., part i. At Roorkee from September, At Lahore from January, 1889, to May, 1905. At 1879, to August, 1904. Mussoorie from May to October, 1877 to 1888. (London: Harrison and Sor.s.)

storms with that which occurs in other places. Unfortunately, the factor that has been used is not given, but it is probably the old erroneous factor 3. It is in few years that this velocity exceeds 50 miles per hour-37 on the present scale of the Meteorological Office and there are few stations on the British coast at which this is not often exceeded. One instance of 90 (66 corrected) is given.

It does not seem unlikely that the violence of the tropical hurricanes is somewhat overestimated owing to the contrast with the usual calm of the tropics, and also, perhaps, because the proximity of violent winds from different directions produces a very irregular and dangerous sea.

The memoirs also contain curves showing the direction and magnitude of the daily variation. The results for St. Helena have lately been treated in a similar manner with very interesting results. The daily oscillation of the barometer, more particularly the second term in the harmonic series with the twelve-hour period, must be associated with the transfer of a considerable mass of air from place to place, and it is of interest to try and trace this transfer in the anemometric records from various parts of the globe. These variations, as they are shown at the mouth of the Ganges and in Northern India, are very fully discussed. The conditions are naturally very different at the different stations, both in space and with the changing seasons, and the causes that produce local winds are so complex that it is almost hopeless to try and correlate cause and effect. At all the stations the change from hour to hour seems to be large by day and small by night, from which one may perhaps conclude that local heating by the sun plays an important part in the pheno

mena.

Although the observations at Mussoorie were only taken during the summer, they are of especial interest, since the station stands on the summit of one of the outer ridges of the Himalayas at an elevation of some 6500 feet above the sea. The hourly and monthly values, as at the other inland stations, are very complex; but there is, as might be expected, a distinct tendency for the air to run up the slope of the mountains during the day and down during the night. Naturally, also, the winds are stronger than at the stations in the plains.

front, partly from the side. This curious disposition of the branching is met with, not only at Cretas, but also at Cogul (Lerida), and in France in the reindeer drawings of the Portel grotto. This points to a closer connection in late Quaternary times of the tribes of Aragon and Catalonia with those of the Ariège than with any others.

The second part of the article describes a series of rock paintings at Cogul, in Lerida (Catalonia), which was brought to the public notice in 1907. The surface painted measures about 2 m. across, and lies beneath a ledge of rock. Altogether there are five distinct pictures. Two are hunting scenes, of which the figures are drawn schematically. M. C. Rocafort regards this as a hieroglyphic inscription, possibly of the Iberian period, but the authors consider that it cannot be thus separated as regards date from the accompanying paintings. The third picture (measuring 75 cm. across) represents a stag surrounded by hinds. The animals of this group are less realistic than those of Cretas, but none the less the execution is delicate, and the attitudes graceful and lifelike.

The right-hand lower scene apparently represents nine women dancing round a man, four being to the right of the man, and five to the left. The man is much smaller than the women, and has no clothing beyond an ornament at the knees; the women are all wearing petticoats reaching to the knees, while the upper part of the body is bare. The figures are painted in black, red, or black and red; the man is dark brown rather than black. The outlines of the four right-hand figures are emphasised by engraving. The whole group measures 68 cm. across.

The dress of the women presents a superficial analogy with the Cretan series, but the lifelike character of the Minoan figures and many details are in strong contrast with the stiffness of the Cogul 66 'ladies." Much more definite evidence would be necessary in order to establish any connection between the two series.

The style of the animal frescoes at Cogul, as of those of the Calapatà (Cretas), is that of our Quaternary drawings, not of later art. This indication is corroborated by the presence, not far from the painted rock at Cogul, of small Magdalenian stations with numerous flint flakes (in some cases retouched) of the type usual in France. Thus it is certain that in the immediate neighbourhood of the painted rocks there existed stations of the late Palæolithic age, contemporary with our civilisation of the Reindeer age; it is also highly probable that the whole of these openair frescoes are to be attributed to the peoples living there; those of single animals afford further beautiful specimens of Quaternary art in animal-drawing. The hunting pictures at Cogul introduce a historic scenic episode as yet unknown in mural art. The dancing scene described raises a small corner of the veil drawn over the social life of those remote ages, and the style of dress tells us something of the use to which the Magdalenian seamstresses put those fine eye-needles which the caves of the Cantabrian Mountains, the Pyrenees, and Dordogne have so long yielded to the astonished eyes of investigators.

ROCK PAINTINGS OF THE LOWER EBRO. VERY interesting article on this subject by MM. A l'Abbé Breuil and Juan Cabré appeared in the January-February number of l'Anthropologie. The first part of the paper deals with the painted rocks on the Calapatà at Cretas (Teruel) first observed by M. Cabré in 1903, although it was not until 1906 that he communicated his discovery, having then realised its significance in relation to Quaternary art. The pictures, which are painted under a shallow shelter, represent animals in various attitudes, and show considerable vigour of execution. Close by, flint flakes are to be found which exhibit no Neolithic characters, but rather Magdalenian. The paintings comprise three deer, a bull, and a small subject difficult to determine. All are done in dark red, and are outlined by a very lightly engraved line; certain details, such as eyes and nostrils, are added in the same way, as they would not otherwise appear in a monochrome ΤΗ without shading. The first deer, measuring 30 cm. HE unexpected decease of Prof. Hugh Blackburn, who occupied the chair of mathematics in the by 25 cm., is represented in a graceful attitude in University of Glasgow from 1849 to 1879, was the act of rising to its feet; the second (33 cm. by announced by Principal Sir Donald MacAlister to the 27 cm.) is walking rapidly towards the first, the great audience of students and friends assembled to movement being admirably depicted. It is interesting hear the inaugural address of Prof. Gibson. The to note that in all the stags drawn in profile the news came as a great shock to such former students antlers are conventional, as if seen partly from the were present, among them his then retiring

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PROF. HUGH BLACKBURN.

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Principia." Later, Prof. Blackburn published a revised and extended edition of Sir George Airy's treatise on trigonometry from the "Encyclopædia Metropolitana," which appeared in a separate cabinet form in 1855.

William Thomson entered in 1846 on his splendid tenure of the chair in natural philosophy in Glasgow, which he filled for fifty-three years. Two years later his father, the professor of mathematics there, died unexpectedly, and it was probably largely due to Thomson's entire conviction of the exceptional mathematical ability of his friend that Prof. Blackburn was appointed in 1849 to succeed Prof. James Thomson.

successor, Prof. Jack, and Prof. Gibson himself, and Prof. Blackburn's old student, colleague and life-long friend, Prof. Ferguson. It was well known that Prof. Blackburn's health had broken down seriously in the spring, and that there had been no sensible improvement, but the actual news was unexpected. Prof. Blackburn's family have been connected with Glasgow for at least three centuries. An ancestor of his, Peter Blackburn, was one of the " regents" of the slowly growing University, from 1574. He was appointed when the Town Council handed over to the University grants made to themselves of lands and buildings by Queen Mary in 1567. From that time until Peter Blackburn was appointed a regent in 1874 the University had been all but moribund. His students always felt for him the greatest affecBlackburn was brought from St. Andrews, where he tion and respect. Every teacher's qualities are aphad graduated, and he acted as regent shortly before praised by the world very much as Mr. Lowe used to the arrival of the great reformer Andrew Melville. judge primary teachers under the famous revised code During Melville's epoch-making six years as prin--by results. Prof. Blackburn had many distinguished cipal, and for two years after it, Mr. Blackburn acted pupils who took high places in the mathematical as third or principal regent. The regents used world. I may name Dr. Thomas Muir, who was an each to take the students committed to them through admirable assistant to the professor, and who has all their subjects, and for their whole university never, in spite of his engrossing duties as director of course. Melville revolutionised this system, setting education in Cape Colony, intermitted his work on each regent to teach some special branch of the determinants. There was Sir Charles Abercrombie graduation course to all the students. Mr. Black- Smith, formerly Auditor-General in Cape Colony and burn was, in fact, "professor" of physics and astro- now Vice-Chancellor of the Cape University; Mr. nomy in the modern sense until he left for Aberdeen, Dickson and Mr. Dodds, formerly tutors of Peterhouse; two years after Melville had left for St. Andrews. Prof. Pinkerton, of Cardiff, and Mr. Nixon, of Balfast. But Prof. Blackburn was much more than a mere mathematician. His university speedily discovered his administrative and financial strength, and made him successively convener of its library and its finance committees. Mr. Blackburn was, perhaps. more trusted and more responsible than any of his colleagues in the removal of the old college from the site it had occupied for four centuries, after it had become unsuitable and perhaps insanitary, to the present splendid buildings. Among his colleagues his authority was always great, and he owed this to the strength and simplicity of his character, and to the clearness of his practical and judicial mind. Students and colleagues alike, who knew him better than others could,

It is curious to find the name Peter surviving after three centuries in the family of which Prof. Blackburn was a member. His eldest brother was Peter Blackburn, long M.P. for Stirlingshire and chairman of the Edinburgh and Glasgow Railway before it was merged into the North British. His second brother, Colin Blackburn, afterwards the famous Lord Blackburn of the High Court of Appeal, was eighth wrangler in 1835, and Hugh Blackburn, the youngest brother, was fifth wrangler in 1845. It was a memorable year at Cambridge. William Thomson,

after

wards Lord Kelvin, then a boy of eight, came across from Belfast to Glasgow, where, in 1832, his father had been appointed professor of mathematics. At the age of twenty-one he was second wrangler and first Smith's prizeman, and founder and editor of the famous Cambridge and Dublin Mathematical Journal.

To its first volume Prof. Blackburn contributed a paper on the variation of elements in the planetary system. Nothing quite like that first volume had previously appeared in the British mathematical world. Side by side with Prof. Blackburn's paper were one by Cayley (senior wrangler in 1842); a note on induced magnetism on a plate, by William Thomson; a paper by Sir William Rowan Hamilton, Irish Astronomer Royal; and another on quadrature of surfaces of the second order, by Mr. John H. Jellett, fellow and tutor, and afterwards provost, of Trinity College, Dublin. In the same volume there were papers by Leslie Ellis, senior wrangler in 1840; by Boole, afterwards the famous professor at Cork; by Augustus de Morgan, London; by Stokes, senior wrangler in 1841; by D. F. Gregory, fifth wrangler in 1837; by Townsend, of Dublin, and Liouville, of Paris, with four other papers by the young editor himself. In that splendid galaxy of men of mathematical genius Prof. Blackburn took a distinguished place, and he had deeply impressed his friends, and Thomson, no doubt, in particular, by inventing and exhibiting in his rooms his well-known pendulum with double suspension. A little later the two young Scotchmen, Thomson and Blackburn, went to Paris together on a mathematical and physical pilgrimage, and all their lives they remained attached and devoted friends. In 1871 they published together the full text of Newton's

honoured him and believed in him. Of a sensitive and artistic nature, he did not, however, care, after

thirty years, to continue services which increasing

deafness made irksome and difficult.

For years, Prof. Blackburn, in declining strength and health, never left the estate, beyond the Mull of Ardnamurchan, where he had found a home in 1879, and where he died. W. J.

NOTES.

SIR RAY LANKESTER Writes to inform us that he has heard from the representatives of the late Prof. Anton Dohrn to the effect that the Zoological Station at Naples remains the property of the heirs of its founder. Neither the German Government nor any German society have acquired any rights in its future disposition. Dr. Reinhardt Dohrn, who has for two years been the acting director of the Zoological Station of Naples, is now director, and has inherited from his father (by agreement with his brothers) the actual property and the leases granted by the Naples municipality as to the site. We wish Dr. Reinhardt Dohrn success and happiness in carrying on the work of his eminent father.

THE Meteorological Office has received reports of observations of an aurora on the nights of October 17, 18, and 19, at several places in England, Scotland, and Ireland. An aurora is also reported in the French Bulletin International as having occurred at Haparanda on the night

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