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done in the way of rabbit extermination. In the meantime known as New Zealand flax, grows in the swamps. only laboratory experiments will be carried on. Finally, there are numerous plants eminently suitable for cultivation, to mention only the Veronicas, Senecios, and

We have received a copy of the meteorological observations made at forty-four secondary stations in the Philippine Islands during 1903. The observations are published for four-hourly intervals from 2h. a.m., and occupy 1128 large octavo pages; the records have been carefully examined under the superintendence of Father Algué. He points out that the Philippines are preeminently agricultural, and that most of the inhabitants are engaged in tilling the soil; consequently temperature, sunshine, and rain are the chief factors to be considered. Rain is the most important element, as sunshine and temperature are generally quite uniform and favourable. 1903 was a bad year for agriculture; drought was prevalent during the first half, while there was considerable rainfall during what is usually considered the dry season. Owing to the drought,

the havoc wrought by locusts was terrible; time after time swarms swept over the land devouring the standing crops, and leaving the country-side bare and dreary.

We have received a copy of the meteorological chart of .the Indian Ocean and Red Sea, issued by the Meteorological Office, for September. This valuable publication gives important information for seamen, including the routes recommended, under steam and sail respectively, between several of the principal ports. The wind roses, which are drawn generally for areas of 5° of latitude by 5° of longitude, show the average conditions for the month from records extending over a period of fifty years, and the direction and rate of the ocean currents are indicated in the usual way, from the results of observations obtained during a period of sixty-five years. In addition, any facts of recent date likely to be of interest are made known, among which we may mention a telegram from the Indian Meteorological Office, dated August 10, with reference to the south-west monsoon between Aden and Bombay, and to the unusually quiet weather conditions in the Bay of Bengal.

WE learn from an article in the August number of the Popular Science Monthly that the Government of the United States intends to repeat so much of the triangulation of the coast and geodetic survey as lies within the area affected by the earthquake of April 18 last, and to carry the work far enough eastward to connect the re-determined points with stations that may safely be regarded as quite beyond the effect of the recent disturbance.

THE flora of New Zealand presents many exceptional features, and it has been Dr. Cockayne's service to describe various strange vegetable productions of these and adjacent islands in his charming and graphic writings. In a series of ten articles that were printed in the Lyttelton Times during May he has provided a general account forming an epitomised survey of the ecology of New Zealand. Discussing the history of the plants, he adduces evidence obtained from the distribution of such plants as Veronica elliptica in favour of a former land connection with South America. Referring to the forests, he enumerates several types, of which the filmy ferns and epiphytic lilies are extraordinary. On the shore is found the tiny buttercup Ranunculus acaulis, bearing only three small, succulent leaves and its small yellow flower above the sand. The arborescent speedwells and species of Sophora showing peculiar juvenile forms are noteworthy among the shrubs. In the mountain meadows a striking feature is the prevalence of white and yellow rather than blue flowers. Phormium tenax, the plant furnishing the valuable fibre

Olearias.

IN choosing bamboos for the garden it is necessary to take into consideration the power of resistance offered by different varieties to frosts. In Le Bambou (July) the editor, M. Lehaie, contributes some notes on the subject, quoting from his experience in Belgium. Among the hardiest varieties he places Henonis, Quilioi, viridiglaucescens, pubescens, and aurea, all species of Phyllostachys, Sasa paniculata, and Arundinaria Japonica. He also provides a list of bamboos cultivated in Europe during 1906, with their synonyms. An interesting communication by Prof. F. A. Forel points to the identity of Phyllostachys Henonis with Phyllostachys puberula. Among the economic uses of bamboos, M. J. Noguès makes special reference to the pulp for the manufacture of paper.

ANOTHER pamphlet on the rubber-tree Ficus elastica, compiled by Mr. E. M. Coventry, of the Indian Forest Department, was recently published as Forest Bulletin No. 4 of the Government of India. The chief factor determining the distribution of the tree is said to be excessive humidity of the atmosphere. For propagation, cuttings and gooties have been given up in the plantations to which reference is made. New plants are obtained from seedlings raised in seed-beds and transferred to a forest nursery that requires to be surrounded with a stockade to keep out deer. Tapping is effected by making horizontal cuts about half round the tree with a V-shaped gouge. The excess of rubber is allowed to fall on mats placed on the ground; this and the rubber collected from the cuts and bark form three grades. Results tend to show that trees should only be tapped every second or third year.

By an Act passed in 1903, the New Zealand Institute and the Colonial Museum were placed on a new footing. In the Colonial Museum Bulletin, of which the first number has just appeared, a sketch of the history and present position of the museum is found which contains much information as to the progress made in forming a collection of Maori antiquities; it is worthy of note that the natives themselves are deeply interested in the scheme, and have made valuable donations. The number also contains Zealand, and an excellent series of photographs of carvings an important article on the marine mollusca of New and weapons recently acquired by the museum. It is unfortunate that in the mother country we are too parsimonious to spread abroad in this way the knowledge of our national treasures.

THE Ceylon National Review, No. 2, contains an illus trated article by Ethel M. Coomaraswamy on old Sinhalese embroidery, illustrated by a collotype plate and sketches of the different kinds of stitches employed. Nowadays specimens are rare; formerly many objects were thus decorated, especially betel bags, which have been preserved in fair numbers. The colours employed were three, red, blue, and the undyed thread; the designs were geometrical, or taken from plants or animals. Most of the work was done with the chain stitch, and the knowledge of it is now confined to the old men in out-of-the-way villages.

IN Biologisches Centralblatt for August 15 Dr. J. Gross concludes his paper on the relationships between heredity and variation. According to the author, there may be two lines of development, fluctuation and mutation, the three stages of the former resulting respectively in the production

of races, species, and genera, while the first stage of the latter corresponds to De Vries's and the second to Mendel's mutation. The Rev. E. Wasmann, in the second article, discusses the comparatively recent development of new species of "commensural" beetles of the family Staphilinidæ in the nests of ants and termites. In the black and red beetles of the genus Dinarda, for example, there are races or species corresponding to the various races or species of ant with which they are associated, and as the differentiation of the ants appears to be comparatively rerent, that of the beetles must, a fortiori, be still more so. In the third article Maria Countess von Linden describes certain very remarkable variations in the shape and colour of the wing-scales of the swallow-tail butterfly Papilio podalirius during the pupa-stage as the effect of external influences. It is noticeable that the scales on the orange spot differ from those of the rest of the wing. The basilar membrane in the ear of parrots, in connection with Helmholtz's resonance-theory, forms the subject of the concluding article, by Mr. A. Denker.

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THE contents of Nos. 1 and 2 of vol. xxviii. of Notes from the Leyden Museum are largely devoted to the description of new genera and species, a number of these being described by Mr. G. Ulmer in a paper on European trichopterous insects. Of more general interest is the description, by Dr. E. D. van Oort, of a new bird-of-paradise (Neoparadisea ruysi) from New Guinea, representing a generic type by itself, and also Dr. Jentink's separation of the large duiker antelope of Rhodesia from the West African Cephalophus sylvicultor, under the name of C. coxi.

THE New Zealand fern-bird (Sphenoeacus punctatus) forms the subject of the first article, by Mr. J. C. M'Lean, in the July issue of the Emu, while in the second paper Mr. H. S. Dove gives notes on a number of New Zealand birds, inclusive of introduced species. In a later communication Mr. E. Scott contributes some interesting information with regard to Dampier's observations on Australian birds made during the voyage of 1689. Mystery attaches to the meaning of the term "gladdens," which the great navigator employed to designate certain birds associated with oyster-catchers and cormorants.

THE whole of vol. xxvii. of Notes from the Leyden Museum is occupied by Miss C. M. L. Popta's description of the fishes collected during Prof. Nieuwenhuis's expeditions to central Borneo in 1898 and 1900. The collection contained a large number of new forms, which have, however, for the most part been named in previous communications. The more important species are illustrated by photographs from original specimens.

SEASIDE natural history, illustrated with a number of excellent photographic plates (in some cases reproduced from Johnston) of zoophytes, &c., occupies a prominent position in the July issue of the Museum Gazette. The addition of a large education museum to the garden city" at Letchworth is strongly advocated.

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Is its report for 1905, published in the August issue of Nature Notes, the Selborne Society takes occasion to refer to the necessity for more active workers and larger funds if its objects are to be fully and efficiently carried out. The enclosure at Ealing for the protection of birds is reported to have been a marked success during the nesting

season.

A PAPER by Mr. David Heron "On the Relation of Fertility in Man to Social Status, and on the Changes in

this Relation that have taken place during the last Fifty Years" has been published in the series of Drapers' Company Research Memoirs (Studies in National Deterioration). Mr. Heron takes as his starting point the legitimate birth-rate for the different districts in London for the years 1851 and 1901, and proceeds to calculate for each year the correlation between this and various measures of their social and economic conditions. By this method he shows conclusively that in both these years a low birthrate is associated with satisfactory conditions and a high one with poverty and improvidence, but that in 1901 this coincidence is far more strongly marked than in 1851, and that whereas in the middle of the last century it could be more than accounted for by the fact that the wives of the upper classes marry at a later age than those of the lower, at the present time this factor is only responsible for about half the difference. It is perhaps unfortunate for Mr. Heron that his paper has appeared after two others dealing with the same subject (Newsholme and Stevenson, and G. U. Yule, Journal of the Royal Statistical Society, vol. xix., part i.), as his methods are very different from, and his conclusions quite independent of, either of them. But owing to the striking way in which these three important papers confirm and supplement one another, it may be to the advantage of the public that they should have appeared in the same year, for warnings of this nature have more chance of obtaining a hearing when they are given simultaneously from different quarters.

IN the Journal of the Franklin Institute of Philadelphia (vol. clxii., No. 1) Mr. Clifford Richardson gives an exhaustive series of analyses of the petroleums of North America, and compares the character of those of the older and newer fields.

A VERY simple and convenient method for calibrating thermometers for use in the determination of freezing points of aqueous solutions is described by Messrs. Richards and Jackson in the Zeitschrift für physikalische Chemie, 1906, Ivi., 362. The thermometer to be tested is immersed in a mixture of powdered ice and water contained in a Dewar vessel, and hydrochloric acid is then added until the requisite temperature has been attained. The true temperature is determined by the concentration of the acid solution in equilibrium with the ice, and this can be ascertained from the table given by the authors, in which acid concentrations corresponding to temperatures between o° C. and -5° C. are recorded.

In a previous measurement of the relative proportion of radium and uranium in radio-active minerals, a neutral solution of radium bromide was employed as standard. It has since been observed, however, that such neutral solutions gradually deposit some of the active substance on the walls of the containing vessel, and this has made a new determination of the proportion of radium to uranium necessary. The number now found by Rutherford and Boltwood (American Journal of Science, iv., 22 [127], pp. 1-3) for the quantity of radium associated with 1 gram of uranium is 3.8 × 10- gram, which is about one-half that obtained in the first experiments.

4 IN the Journal of Physical Chemistry, 1906, vol. x., p. 445, Messrs. Carveth and Magnusson give an interesting account of the evolution of the apparatus for the determination of the boiling points of solutions for the purpose of molecular weight measurements. The advantages and disadvantages of the various types are discussed, and a new form of apparatus is described, the distinctive features of

which are a separate boiling flask and a return condenser provided with mercury trap. With a this apparatus measurements can be made very quickly, and the parts liable to break are easily replaceable.

IN the same journal Mr. R. C. Snowdon shows that metallic lead can be electrolytically deposited in a satisfactory and adherent condition from an acidified solution of lead acetate. This result is attained by employing a rapidly rotating kathode and a virtual current density of 1.5 amperes per square decimetre, and adding about 1 gram of gelatin to a litre of the solution. In an investigation of the behaviour of ferromanganese anodes in solutions of caustic soda, Mr. G. R. White finds that permanganate is formed irrespective of the current strength and the concentration of the solution. Metallic manganese yields permanganate at high current densities, but manganous hydroxide is only oxidised to dioxide. The electrolytic formation of permanganate is therefore a direct reaction, the lower oxides not being formed as intermediate products. WE have received from Messrs. Adam Hilger, Ltd., a copy of their "List A" of spectroscopes and spectroscopic accessories. This list contains descriptions and illustrations of the numerous specialities manufactured by the firm, and should be consulted with interest by all workers in spectroscopy. The spectroscopes, spectrographs, and accessories of especial interest are too numerous to be referred to here, but mention may be made of the fact that the firm is now prepared to supply the strips of plane parallel glass, up to 300 mm. by 40 mm., used in the Lummer and Gehrcke parallel plate spectroscope described in the Annalen der Physik, vols. x. (1903) and xx. (1906). These strips may be used with any ordinary spectroscope of suitable size, but the firm will be pleased to quote prices for specially designed instruments.

THE new edition of the Japanese Pharmacopoeia, which has been in preparation for some considerable time, has now been completed, and will be issued shortly. Among the alterations in it is the substitution of Japanese characters for the names of drugs and chemicals for the Chinese forms hitherto used.

A NEW magazine, entitled the University Digest, is announced for publication by the University Research Extension of Chicago. Its aim (to quote from the prospectus issued) is "to keep before its readers the ideal phenomena that distinguish the modern, the greatest of world-epochs," and the intention of its promoters is to represent the results of scientific research in religion, philosophy, and the social and natural sciences. The periodical will be issued at monthly intervals from September next, excluding the months of July and August.

THE Proceedings and Transactions of the Nova Scotian Institute of Science for the session 1903-4, just received, contains many papers of value. The address of the president Dr. H. S. Poole-dealt with the progress of the institute and the application of science to mining, and among other communications in the volume we notice the following the earthquake of March 21, 1904, in Nova Scotia, by Prof. J. E. Woodman; swim bladder of fishes a degenerate gland, by Prof. E. E. Prince; and determination of elements of terrestrial magnetism at Halifax, Nova Scotia, August, 1904, by Prof. S. M. Dixon.

THE official year-book of New South Wales for 1904-5 has just reached us. It is edited by Mr. W. H. Hall, acting statistician to the State of New South Wales, and

is a mine of information, containing as it does papers on the discovery of "Terra Australis," the physical configuration, the geological formation, the meteorology, vegetation. timbers of commercial importance, fish and fisheries, and fauna of New South Wales, besides much information of statistical importance. The volume is illustrated by some twenty-eight well-executed figures, and should be seen by all who are specially interested in the State under review

THE twenty-sixth annual report of the Manchester Microscopical Society, which has just been issued, tells of continued progress. The address on precious corals de livered by Prof. S. J. Hickson, F.R.S., as president, is to be found in the volume, as is also an illustrated paper by Mr. M. L. Sykes on animal coloration.

THE seventh annual report of the Museum and Art Gallery of Plymouth is of an encouraging nature. During the year ending with March last many interesting additions were made; the public lectures on subjects connected with the work of the museum were, it is stated, on the whole decidedly successful. The museum and gallery were visited during the period under review by 30,760 persons.

A NEW (the second) edition of "The Geology of the English Lake District, with Notes of the Minerals," by Mr. J. Postlethwaite, has just been issued by G. and T Coward, Carlisle. The little book has been revised and additional lists and plates of fossils have been added, and the section on the Mollusca of the Skiddaw slates has been rearranged.

THE current number of the Monthly Magazine contains a very readable account, by Mr. H. W. Strong, of the evolution of the turbine, entitled "The Coming of the Turbine "; it has also an interesting paper by Mr. A. W. Rees on a moorland sanctuary.

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Ioh. 47m. Minimum of Algol (B Persei). Vesta N. of star 105 Aquarii (mag. 4'7). 11. Vesta (mag. 65) in opposition to the Sun. 15. Venus. Illuminated portion of disc =0'514; Mars =0.989.

16. Saturn. Major axis of outer ring =44′′ 33, minor axis=4" 15.

20.

23.

29.

Ioh. Venus at greatest elongation, 46° 29′ E.
11h.

Sun enters Libra, Autumn commences.

11h. 29m. Transit (egress) of Jupiter's Sat. III. (Ganymede).

30. 12h. 30m. Minimum of Algol (8 Persei). DISCOVERY OF A NEW COMET (1906e).-A telegram fr the Kiel Centralstelle announces the discovery of a new comet by Herr Kopff at the Königstuhl Observatory n August 22.

Its position at 14h. 17m. (Königstuhl M.T.) on the Car of discovery was R.A.=22h. 49m. 32s., dec. = +10° 23, and the amount of its daily movement was found to be -44s. in R.A. and -2' in declination. Unfortunately no idea of the comet's brightness is given.

A second telegram from the same source states that the romet was observed at Hamburg by Herr Graff on August 23, its position at 13h. 11.3m. (Hamburg M.T.) being R.A.=22h. 48m. 53.55., dec. =+10° 21' 7".

From this it is seen that the comet is apparently in the Constellation Pegasus, a little to the north of Pegasi, and is moving in a south-westerly direction. This position crosses our meridian at about 12 o'clock midnight

FINLAY'S COMET (1906d).-This comet will arrive at its perihelion, according to M. Schulhof's elements, September 7.5.

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As shown by the following extract from the ephemeris published in No. 4109 of the Astronomische Nachrichten, the comet is now apparently travelling through the extreme north-eastern corner of Orion towards Gemini, which it will enter on September 9. On September 7 it will pass about 1 south of 71 Orionis, and on September 13 about 1° 36' north of Geminorum. On the latter date the comet will rise about five hours before sunrise, i.e. about 12.30 a.m.

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+19 4 +19 19 GREENWICH SUN-SPOT NUMBERS.-An innovation which is likely to be found a great convenience by everyone who has to discuss sun-spot observations appears in the August number of the Observatory.

Up to the present such workers have had to wait until about the middle of the next year before the serial numbers allotted to the sun-spots of any one year by the Greenwich authorities became available for general use. Now, with the sanction of the Astronomer Royal, Mr. Maunder proposes to publish these numbers month by month.

The first instalment, giving the numbers for the quarter January-March, 1906, appears in the current Observatory. Next month's issue will contain the data for the second quarter, and after that each month will be given separately, so that the numbers for July will appear in October, and

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THE ORIGIN OF THE ZODIACAL LIGHT.-Some interesting observational results, and deductions therefrom regarding the origin of the zodiacal light, appear in a brochure written by Mr. Maxwell Hall, of Montego Bay, Jamaica, and issued as a reprint from the Monthly Weather Review for March, 1906.

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Mr. Hall's observations were made at Jamaica in 1899 and 1901, and determined the breadth of the light and its boundaries at different distances from the sun. ducing the observed latitudes according to their longitudes, or distances from the first point of Aries, Mr. Hall obtained striking evidence which tends to show that the light is parallel to the invariable plane of the solar system, evidence which was apparently confirmed by the results obrained by other observers.

On these grounds Mr. Hall arrives at the conclusion that the zodiacal light is caused by the reflection of sunlight from masses of meteoric matter still contained in the invariable plane, which may be considered as the original plane, of the solar system.

If this conclusion is correct, and the phenomenon is astronomical in its origin, the light should be seen better and more frequently from observing stations situated in high altitudes, and the editor of the Review especially commends its observation to workers located at such stations.

A MODIFIED FORM OF SOLAR EYE-PIECE.-From Prof. Ceraski, of Moscow, we have received a brief description of a solar eye-piece which he is using, and has found to be most effective, for the detailed study of sun-spots. This

eye-piece is analogous to one described by Dawes in vol. xxi. of the Memoirs of the Royal Astronomical Society, but as no one seems to have used this for the study of minute details in sun-spots, Prof. Ceraski describes the one he is now using.

The apparatus is furnished with a positive eye-piece and a copper plate pierced with circular apertures of various diameters, thus forming an adjustable diaphragm. This copper plate is protected by a disc of asbestos which contains a central aperture slightly larger than the largest in the diaphragm. The dark glass is a combination of black mica and blue glass.

Using this eye-piece with the full aperture of the Pulkowa 15-inch refractor, Prof. Ceraski was surprised at the amount of detail seen.

PHYSICS AT THE BRITISH ASSOCIATION. THE proceedings of the Mathematical and Physical Section (A) commenced on Thursday, August 2, with the delivery of the presidential address by Principal E. H. Griffiths, F.R.S. This address has already appeared in full in these columns (August 9, p. 356).

The chief interest of the meetings in this section arose in connection with several discussions which were

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arranged and taken up with avidity. On August 2 the Earl of Berkeley described his experiments on the measurement of osmotic pressure, both directly and indirectly from measurements of vapour pressure. two methods give results agreeing to within 5 per cent. Mr. W. C. D. Whetham followed, and treated the same subject from the standpoint of thermodynamics and the dissociation theory, thereby stimulating Prof. Armstrong to make a vigorous attack on everything connected with thermodynamics and dissociation. In Prof. Armstrong's opinion the secret of osmotic pressure is to be sought in a thirst of complexes of water molecules. He laid stress on the importance of recent work in America, which proved that Boyle's law was satisfied for much greater strengths of solution than was shown by Lord Berkeley's results. In the course of discussion it seemed, however, that the difference was rather one of interpretation of results than of the experimental results themselves. Mr. Whetham, in his rejoinder, declared also in favour of a thirst hypothesis, but differed in regard to the

mechanism of it.

On Friday, August 3, two important discussions took place. The former was opened by Mr. Frederick Soddy, the subject being the evolution of the elements. Mr. Soddy outlined the subject from the earliest times to the most recent developments in connection with radio-active changes. Uranium gradually changes to radium, radium to its emanation and several other successive products, until in all probability it becomes lead. Lead in turn suffers a gradual transmutation into silver. These changes proceed spontaneously, setting free energy as they occur. With regard to active attempts at transmutation in the reverse direction, which, of course, require a correspondingly large supply of energy, Mr. Soddy considers that success will be found first in a nearly complete vacuum carrying an electric discharge. Here there is very little matter carrying a large amount of energy, so that the necessary conditions would seem to be supplied. The Hon. R. J. Strutt laid stress on the fact that in radioactive changes helium was the only non-valent element produced, while in our atmosphere argon was largely preponderant. Had argon been formed by other transmutations? Dr. O. W. Richardson and Dr. H. A. Wilson discussed the apparent disappearance of matter in vacuum tubes, alluding to quantitative experiments made in the Cavendish Laboratory. Prof. Schuster emphasised the nearly complete indifference of radio-activity to temperature changes, the only temperature effect yet discovered being a small one found by Mr. W. Makower working in his laboratory. He had experiments in progress on the influence of high pressures with the aid of apparatus designed by Mr. Petavel. With this apparatus a pressure of 2000 atmospheres can be obtained; no change in radioactive charge brought about thereby had yet been detected,

but the experiments were not yet complete. Prof. S. P. Thompson, in reference to the Cavendish experiments, pointed out that it was well known that gases were absorbed by the walls of vacuum tubes. The Rev. A. L. Cortie, speaking from the astronomical standpoint, was able to declare that radium had not been detected in extraterrestrial bodies, although helium, which is produced during its decomposition, is discovered in the sun. The idea of a primitive substance is very ancient; it is simply the materia prima of Aristotle. A considerable part of the discussion turned on the use (or misuse) of the term atom, a term which Prof. Tilden, speaking as a chemist, was unwilling to give up. Undoubtedly the term has lost its original etymological signification, but its use has become too fixed to expect a change to be readily made. The discussion proved so interesting and stimulating that Mr. Soddy's paper, which gave rise to it, has been directed to be published in full in the report. A more immediate consequence was that the programme for the day was completely upset; a large number of papers had to be held over in order that the next discussion arranged might be taken. The subject was the notation and use of vectors, and Prof. Olaus Henrici opened it. He explained the various notations which have been proposed for vector and scalar products, and proceeded to give examples of their use. He showed how the operator v might be defined without reference to analytical geometry from the relation dUdp. AU, where U-any scalar function of position, and dp length of displacement of the representative point. He then applied the properties of the operator to the deduction, with great simplicity and elegance, of results connected with the theory of partial differential equations. Dr. C. G. Knott followed, and deplored the substitution of vectors for quaternions, and objected that neither scalar nor vector product was really a true product. He advocated a return to the methods of Sir W. Hamilton. He pointed out that Hamilton does not speak of a vector or a scalar product, but of the vector of a product and the scalar of a product. With regard to the change of the usual negative to the positive sign suggested by certain vectorists, he explained that it had compelled Gibbs to introduce a third kind of product, and more recently Jahncke had introduced a third in order to be able to treat of strains. Prof. W. M. Hicks criticised Henrici's use of brackets to denote vector and scalar products on account of liability to confusion. Prof. Henrici, in an eloquent reply, showed how easily all quaternionic results could be derived from vector analysis.

On Monday, August 6, an important discussion took place on radio-activity and the internal structure of the earth, opened by the Hon. R. J. Strutt. From the examination of a large number of rocks, both igneous and sedimentary, he had come to the conclusion that there is much more radium in all of them than would be needed to maintain the earth's internal heat if the earth were constituted of rock throughout. Hence he concludes that the interior of the globe does not contain radium, and that in all probability its composition is quite different in other respects also from that of surface materials. The thickness of the radio-active crust is estimated at forty-five miles at most, which corresponds to an estimated temperature of 1500° C. at its interior surface. The inside nucleus would be at this temperature throughout just as a loaf of bread which has been in an oven long enough takes up a steady temperature equal to that of the oven. In reply to the possible objection that a gram of radium diffused through an enormous volume of rock may not develop nearly so much heat as it would do if concentrated, it was argued (1) that the rate of emission of alpha particles of pitchblende (to which particles the heat is mainly due) is exactly what might be expected on the view that the radium atoms contained in the mineral are as energetic as they would be if they were all collected together, and (2) direct measurements made by Pegram on uranium and thorium have shown that these feebly active elements give about the amount of heat which their activity would lead one to expect. Prof. J. Milne, who followed, directed renewed attention to the bearing on the problem of the three phases of earthquake tremors. The first, for stations connected by small chords, travels at a slow,

nearly constant rate, but for chords penetrating to a depth greater than twenty miles the velocity increases to about 12 kilometres per second, indicating that the wave is carried by something more rigid than the outer crust. Prof. J. W. Gregory, speaking as a representative of the Geological Section, considered that Strutt had struck a blow at the theory of contraction by cooling. We are no longer bound to believe in very high temperatures in the past history of the earth. Arrhenius's theory may now t dismissed. He suggested the importance of mapping a small area completely in regard to the radio-activity of the rocks comprised in it. Sir W. Crookes declared his belief that radium inside the earth may not be so radioactive as at the surface. Pitchblende in Thick masses behaves much the same as in thin layers. An experiment in which 50 mg. of radium were sealed in a glass tube and deposited in a cavity in ice, and an exactly similar tube containing 50 mg. of silica was similarly deposited, showed that neither sank as much as one-thousandth of an inch during prolonged observation. Sir G. Darwin directed attention to the work of Gilbeck, Putnam, and Hayford, of the United States Coast Survey, who had fixed a limit of about seventy miles to the thickness of the crust. Sir Wm. Ramsay suggested that Mr. Strutt should make a special examination of sulphides with the object of finding whether they contained radium. further queried whether alpha particles give out all their energy as heat-a query which must most probably be answered in the negative.

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Mr. R. D. Oldham (also representing the Geological Section) gave distinct evidence, derived from earthquake phenomena, that there must be a central core, the radius of which is about 0.4 of the earth's radius, having rather less resistance to compression than the main body. Prof H. Lamb threw out a warning against laying too much stress on arguments based on observation of earthquake velocities. Too little is known as to effects of pressure and temperature.

Mr. Soddy showed that another explanation of the apparent absence of radium heat might arise from processes of upbuilding going on which may depend upon a possible concentration factor. Prof. Hicks emphasis-d Mr. Soddy's suggestion, and pointed out that eyes cooling might be produced by such building-up processes. He also suggested that the reason temperature does not usually affect radio-active changes is that time comes in as a factor, and he would like to see experimentally whether a very long application of a low temperature would not produce some effect. Mr. Fearnsides indicated that in the most radio-active rocks elements of high atomic weight were associated with those of low atomic weight.

The last organised discussion was held on Tuesday, August 7, the subject being the nature of the radiation from gas mantles. Unfortunately Mr. Swinburne, who was to open it, was unavoidably absent; his paper 5 therefore read by the recorder. It consisted of a spirited outline of the various theories that had been proposed to account for the high luminous efficiency of the Welsback burner, with a declaration in favour of the simple temperature explanation. Low emissivity allows the mantle t approach the temperature of the flame; a substance of greater emissivity could not rise so high in temperatur and consequently the radiation which the latter would give out would not be so rich in luminous qualiti "Though this simple explanation may be ample it des not follow that there may not be all sorts of cures things, such as selective emission, luminescence, ratletic action, resonance, unstable oxidation and other occurrenc whose names are as impressive as vague." Dr B Rubens, of Charlottenburg, followed with an account o the experiments which he has recently conducted and which have been described in Drude's Annalen. Ceria 1 radiations in the immediate infra-red is a very p** radiator, while for luminous and the extreme infrat radiations it behaves much more nearly as a perfecti black body. On the whole, the thoria-ceria mantle s poor emissivity, and its temperature approaches 1600 C.. while the nature of the radiations from the added ceria confers additional richness on the proportion of lumines

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