even if it were not more economical than the best steamdriven machines, was certainly not more expensive. The greater facility and safety with which electricity can be used, the smoothness with which it works, and its much greater flexibility, would often make it preferable to the use of steam, even in a case where transmission of energy was not required; there could be no hesitation in the choice between the two systems when the power had to be transmitted from a distance, or where the production of energy could be centralised at one power station.

M. Ed. Noaillon's paper on ferro-concrete was next read. Ferro-concrete constructions, as is well known, consist of a mass in which iron or steel reinforcement is bedded. The author stated that round bars were generally used, as they facilitated the escape of air and the proper ramming of the concrete; there were also no sharp angles which would cut the concrete. On the other hand, the round section gave the lowest coefficient of adhesion for a given cross-section of metal. The following rules governing the construction had been prepared by Prof. Rabut:(n) No connection should be made of iron to iron, as the concrete itself holds the parts together in the most economical manner. (2) At least two distinct systems of reinforcement should be used, one to take up the tensile stress and the other to take up the shearing stresses in the concrete; when necessary a third system should be used to take up the compressive stresses. (3) The reinforcement should be so arranged that the separate members may be stressed in the direction of their length, so that the stresses produced between the iron and the concrete should be tangential, and not normal to the axis of the members of the reinforcement. (4) Homogeneity of the structure should be taken advantage of by prolonging the iron parts of one portion of the structure into the thickness of the concrete of the adjoining portion. Other points were also given.

Methods of construction were described and illustrated. Some examples of reinforced concrete were given in the paper, the handsome dome of the new Central Railway Station at Antwerp being a prominent instance. This dome is a fine piece of architecture, but was designed first of all for an ordinary masonry structure, a fact which made it somewhat difficult for the architects to adapt it for ferro-concrete. The entire structure is 1800 tons in weight, and rests wholly upon the columns at the angles of the glass lights; these columns are Y-shaped in cross-section. The external shell has a uniform thickness of 3.15 inches, and is relieved by six moulded ribs following the meridian lines. The Renommée Hall at Liége was the next example of this kind of construction. It was designed expressly for the use of this material. The principal hall is covered by three cupolas, each 55 feet in diameter, placed at a height of about 50 feet above the level of the ground. Each cupola forms part of a sphere, which continues in haunches, pierced with lights, and descending to the corners of the circumscribed square. The intersections of the spheres with the vertical spans passing through the sides of the squares are formed by arched beams, which spring from the capitals of short cylindrical columns. The Cupolas are 43 inches thick, and are made of concrete composed of cement clinker finely broken up; they are reinforced by a layer of expanded metal with a lattice work of bars. Members of the institution had a good opportunity to examine this structure, as one of the banquets during the meeting was given in the Renommée Hall.

An interesting application of reinforced concrete was also described in the widening of La Boverie Bridge at Liege. Particulars were also given of another bridge, built upon the Hennebique system; the length between abutments was 260 feet, and comprised a central span of 18c fee and two side spans. The total width of the roadway was 32 8 feet. An interesting feature about this bridge is the design of the foundations, and the way they were rested by mechanical compression of the soil. The piers and abutments rested upon a group of concrete piles driven deeply into the bed of the gravel, which thus became strongly compressed. The concrete piles were reinforced hy vertical bars of steel which were continued into the pies and abutments, so that the whole was solidly bound !gether. By this method the advantage was obtained of schdly rooting the bridge into the earth, so that it

had a resistance amply sufficient in case of a floating accumulation of ice, such as would temporarily transform the bridge into a dam. A skew bridge, also on the Hennebique system, was referred to, and a description was also given of a framework for lead chambers at the chemical works of the Engis Co. In the brief discussion which followed this paper, Mr. W. H. Maw suggested that it would be interesting if experiments could be made upon the effect of tension upon bars held in concrete. He had heard that a better hold of the concrete was obtained if the bars were previously treated to a wash of cement.

Mr. Mellanby's paper on the efficiency of the steam jacket was next read. This paper may be said to form part of a series of contributions on the same subject which have been given by various authorities during recent times. The results of a series of somewhat elaborate trials were given, from which the following general results may be taken. A compound engine, with boiler pressure at 150 lb., may be worked with the mean pressure referred to the low-pressure cylinder of about 40 lb. per square inch without any loss of efficiency in terms of the brake horsepower. Steam jackets have their maximum efficiency when the whole of the high-pressure and the ends of the lowpressure cylinders are jacketed with high-pressure steam. When jackets are applied to the high-pressure cylinder, the total indicated horse-power is slightly reduced, but when applied to the low-pressure cylinder the total indicated horse-power is considerably increased. Jackets have little effect in the high-pressure, but have considerable effect in the low-pressure cylinder upon initial condensation. The temperature supplied to the cylinder walls next to the steam must be considerably less than that of the steam, because, firstly, the actual " missing quantity" is much less than it would have been had the steam and metal gone through the same temperature changes, and secondly, because the mean temperature of the metal is higher than that of the steam. The author concluded that the greater part of the "missing quantity" must be due to leakage, and not to initial condensation, in this respect agreeing with the conclusions of Messrs. Callendar and Nicolson.

A somewhat extended discussion followed the reading of this paper. It was opened by Mr. V. Pendred, who said that compression in the cylinder had a considerable effect. If the compression corner of the indicator diagram was square, the utility of the jacket appeared to be small, but if it were rounded off by compression jacketing appeared to be more effective. Mr. Saxon, of Manchester, took exception to the statement as to a mean effective pressure of 40 lb. being the most efficient for a compound engine; he considered that the ratio of the cylinders should be taken into account. Mr. Henry Davey did not regard the results obtained as a guide for engineers, on account of the bad performance of the engine. Mr. Mark Robinson confirmed the author's opinion in regard to a mean pressure of 40 lb., and, in reply to a remark of Mr. Saxon's, said that the size of the cylinders should be in accordance with the power needed, and their ratio should be governed by the conditions of working.

On the second day of the meeting the first paper taken was a contribution by Mr. R. Mathot on large gas-engines. This was a long and interesting paper, containing a considerable amount of historical matter, and dealing with many of the details of construction by Continental makers in the design of large gas-engines, which have formed so prominent a feature of the engineering of Germany and Belgium within the last few years. The paper was illustrated by a number of engravings and diagrams, and results of engine tests were given in a table. Although English engineers early took the lead in the manufacture of gas-engines of moderate size, they have been to some extent left behind by Belgian and German manufacturers in regard to large gas-engines using blast-furnace gas: and even such of the latter as have been constructed in England have been mostly to German designs. It would be impossible in a report of this nature to give an account of the many details of construction dealt with by the author, especially without the aid of the numerous illustrations by which the paper was accompanied.

The discussion that followed the reading of the paper mainly consisted of a speech by Mr. Crossley, of Man

chester, who defended the position of the English gasengine makers, pointing out what had been done in the past. He did not, however, deny that the Continental makers were in advance of the English makers in regard to the size of the gas-engines manufactured.

The remaining paper was Prof. Lilly's contribution on the strength of columns, but the time for adjournment having arrived, this was only read in brief abstract, and was not discussed.

A large number of excursions and visits to works in the neighbourhood of Liége had been arranged by the local committee. Visits were also paid to the exhibition, and there were the usual social functions, including the reception, the dinner at the Renommée Hall already mentioned, and the institution dinner held at Liége. Thursday was entirely given up to these excursions, and on Friday members travelled to Antwerp, where they viewed the extensive docks of that city and some of the works in the neighbourhood. This brought a very successful meeting to a close.

UNIVERSITY AND EDUCATIONAL

INTELLIGENCE.

OXFORD. Dr. Ritchie, Fellow of New College, the present reader in pathology, has been constituted professor of pathology so long as he continues as reader. Dr. A. J. Herbertson, non-collegiate, has been appointed university reader in geography.

The Rev. H. T. Morgan, Trinity College, has offered to continue the unfinished carving in the corridors of the university museum. Much of the elaborate plan for the sculptural decoration of the museum, undertaken in 1860, has remained uncompleted, and the Rev. H. T. Morgan has generously undertaken to provide for the carving of the capitals and corbels of at least two of the four upper corridors. The delegates propose to continue the original plan, according to which the capitals were to represent various plants in systematic order.

On June 20 a deputation from the medical graduates of the university, Sir William Church, Dr. Sharkey, Dr. Shornstein, Dr. Collier, and Mr. Whitley, presented an address to the Vice-Chancellor urging the importance of pathology in the medical curriculum of the university, and stating the steps that have been taken to provide permanent endowment for the teaching of this subject. A " pathology endowment fund" has been started, and an appeal that was limited to members of the profession has resulted in the contribution of more than 500l. A member of the university, who has already given 1000l. towards the endowment of a pathology chair, has offered to cover all subscriptions from the medical faculty by an equal amount.

It is announced that General W. J. Palmer, of Colorado Springs, Col., and Mr. Andrew Carnegie have given respectively 20,000l. and 10,000l. as a nucleus to the 100,000l. endowment fund for Colorado College.

MR. T. P. BLACK has been appointed demonstrator in physics in Armstrong College, Newcastle-upon-Tyne. Mr. Black was a student of the college from October, 1900, to June, 1903, when he was elected to one of the Royal (1851) exhibition scholarships.

WE learn from Science that the proposed affiliation of the Massachusetts Institute of Technology with Harvard University was approved at a meeting of the corporation of the institute on June 9. It was agreed to accept the terms of the agreement recently drawn up by the committee of the two institutions. Before the agreement can become effective the corporation and overseers of Harvard University must take action, and several legal questions must be settled.

THE Committee appointed to inquire into the present condition of fruit culture in Great Britain, and to consider whether any other measures might with advantage be

taken for its promotion and encouragement, has reported to the Board of Agriculture in favour of the establishment of a special sub-department to deal with matters connected with the fruit industry. The main recommendation is that there should be two branches of such subdepartment-(a) a bureau of information, (b) an experimental fruit farm. It is further proposed that horticulture should be taught in elementary schools in country districts, that such schools should have gardens attached wherever possible, and that the attention of local education authorities should be directed to this, and also to the desirability of encouraging the study of practical herticulture in training colleges.

THE programme of the summer meeting of university extension students, which is to be held at Oxford in August, has now been published. The lectures in the natural science section will be devoted to an explanation of the scientific method and to the illustration of its application to scientific work. General introductory lectures will be delivered by Prof. T. Case, on the scientific method as an operation of the mind, and by Prof. F. Gotch, F.R.S., on the development of the scientific method. Special lectures illustrative of the applications of the scientific method to numerous branches of science have been arranged, and these lectures will be directed to show the extent to which the general conception of the particular science has been developed by the use of the scientific method, and the way in which the method is used in the experimental investigation of some group of phenomena. Among the varied list of lectures from which students may choose we notice those by Prof. W. F. R. Weldon, F.R.S., on variation and heredity; by Prof. C. S. Sherrington, F.R.S., on a general survey of physiology and psychophysics; by Prof. W. M. Flinders Petrie, F.R.S., on crucial instances in archæology; and by Dr. G. J. Burch, F.R.S., on modern conceptions of matter.

MR AILWYN FELLOWES, President of the Board of Agriculture, presided at an agricultural conference held at Aberystwyth last week. The object in view in holding the meeting was the extension and development of the work of the agricultural department of the University College of Wales by the establishment of a more definite connection between its extension work and that done inside the college, and by better organisation of the department of agriculture itself. Mr. Fellowes said that the Board of Agriculture has been able to give 8ool. a year to Aberystwyth College and 200l, a year towards the college farm which was opened the same day. The college is also largely aided by the residue grant which since the year 1890 has been handed over to the county councils of the kingdom. In the counties connected with Aberystwyth College, one-sixth of the residue grant has been given to agricultural education. Mr. Fellowes said he hoped, as time went on and as Imperial funds improved, that the Board of Agriculture will be able to do more for agricultural education and for agricultural colleges. He strongly commended the suggestion that a descriptive pamphlet should be issued by the college authorities setting forth what are the proceedings of the college and what young men are able to learn there. It was decided to ask the county councils to appoint representatives to consider the details of a scheme of organisation for the agricultural department at a conference to be held in October. The following resolution was passed-that this conference desires to record its warm gratitude to the Board of Agriculture for the invaluable aid it has rendered to agricultural education in the counties affiliated to the University College of Wales at Aberystwyth. The conference is of opinion that the results already attained and the response to the help and guidance received from the Board by the local authori ties out of their limited resources constitute a strong claim for largely increased grants from the central Govern ment towards agricultural education, which is a matter of the highest importance in the interests of the kingdom and the Empire at large. In the afternoon Mr. Fellowes opened the recently acquired college and counties' training farm, which is situate about four and a half miles outside Aberystwyth, and has an area of 200 acres.

SOCIETIES AND ACADEMIES.

LONDON.

Geological Society, June 7.-Dr. J. E. Marr, F. R.S., president, in the chair. The microscopic structure of minerals forming serpentine, and their relation to its history: Prof. T. G. Bonney and Miss C. A. Raisin. The authors embody their investigations in the following conclusions :—(1) That both a tint and pleochroism are accidental rather than essential characteristics of antigorite. (2) Neither are low polarisation-tints characteristic, unless two mica-like minerals exist, otherwise indistinguishable. (3) That it is doubtful whether any hard and fast line can be drawn between antigorite and the more fibrous forms in ordinary serpentine rocks. (4) That the most typical antigorite appears when the rock has been considerably affected by pressure, but it becomes less so when the latter has been very great. (5) That so far from the nearly rectangular cleavage of augite originating the "gestrickte struktur," it is worse preserved than any other original one in the process of serpentinisation. Typical antigorite, however, apparently is rather more readily produced from augite than from the other ferromagnesian silicates, but is more directly a consequence of pressure than of chemical composition. The tarns of the Canton Ticino: Prof. E. J. Garwood. The lakes dealt with comprise the larger Alpine tarns which occur in the Canton Ticino. Most of these drain into the Ticino basin; one or two, however, flow into the Reuss or the Rhine. These lakes owe their origin, when they are rock-basins, to the presence of lines of weakness, along which in many cases solution has taken place, while in some shallow tarns ice may have removed detached fragments; but in no case has a lake been found which can reasonably be assigned to ice-excavation independent of rock-structure.

Mineralogical Society, June 14.-Prof. H. A. Miers, F.R.S., president, in the chair.-The chemical composition of lengenbachite: A. Hutchinson. A quantitative analysis of the new mineral from the Binnenthal recently described by Mr. R. H. Solly leads to the formula 7PbS.2As,S,, part of the lead being replaced by silver and copper, and part of the arsenic by antimony. The chemical composition of hutchinsonite: G. T. Prior. Chemical examination of this new and extremely rare mineral from the Binnenthal described by Mr. R. H. Solly showed that it could be added to crookesite and lorandite as a third mineral containing the rare element thallium as an important constituent. Quantitative analysis, made on a small amount of material (about 70 mg.), showed the presence of about 20 per cent. of thallium, and suggested the formula (TI,Cu,Ag),S.As,S,+ PbS.As,S,. -The identity of the amiantos of the ancients with chrysotile: Dr. J. W. Evans. The principal source of amiantos appears to have been Cyprus. Specimens brought by Prof. Wyndham Dunstan from the ancient workings on the slopes of Mount Troodos prove to be chrysotile, and not tremolite asbestos. A chemical analysis by Mr. G. S. Blake confirmed this result.-Gnomonic projection on two planes at right angles: Dr. J. W. Evans. By means of these projections and the rotation of one plane on an axis at right angles to the other, simple solutions of crystallographic problems are obtained.-The President exhibited supersaturated solutions of sodium nitrate showing the transition from the metastable condition, in which crystallisation is only possible in the presence of solid crystals, to the labile condition, in which the liquid can crystallise spontaneously.

Physical Society, June 16.--Prof. J. H. Poynting, F.R.S., president, in the chair.-On the ratio between the mean spherical and the mean horizontal candle-power of incandescent lamps: Prof. Fleming. This paper contains a theoretical deduction from first principles of experimental results given by Mr. G. B. Dyke in a paper read before the Physical Society on November 11, 1904, respecting the ratio of the M.S.C.P. of incandescent electric lamps to the M.H.C.P. taken when the lamp was rotating round a vertical axis. In the case of nine different types of electric

glow-lamps, this ratio was found to be a number near 0-78. The author shows, by discussing the simple case of linear filament, that the ratio of the M.S.C.P. to the horizontal candle-power for this last case must be represented by the value 40-785, and hence that the constant ratio found experimentally by Mr. Dyke necessarily follows as a simple consequence of the fact that the light sent out in any direction from each unit of length of an incandescent filament varies as the cosine of the angle of inclination of the ray to the normal to the filament. In the paper it is shown also how a simple correcting factor may be obtained for reducing the actual horizontal candle-power of a linear filament of finite length to the candle-power in the same direction which would be found if the elements

of the filament were concentrated on the axis of the photometer and all normal to it.-The electrical conductivity of flames: Dr. H. A. Wilson. The paper contains an account of a series of experiments on the conductivity of a coal-gas flame for electricity between platinum electrodes immersed in the flame. The variation of the current with the distance between the electrodes and the fall of potential along the flame are investigated by using a special burner producing a long narrow flame. The burner consists of a fused quartz tube with a series of small holes parallel to its diameter. The electrodes are two parallel discs of platinum, one fixed at one end of the flame, and the other capable of movement horizontally in the flame, so that it be placed at any desired distance from the fixed electrode. The current through the flame was measured by a moving coil galvanometer, and the potential difference between the electrodes by an electrostatic voltmeter. The quartz-tube burner being a good insulator enables a current to be passed from one end of the flame to the other without fear of any of it going through the tube instead of through the flame. It thus enables the effect of putting salts into different parts of the flame to be easily studied.-Contact with dielectrics: Rollo Appleyard. Among the conclusions arrived at are the following:-(a) Except in the case of homogeneous dielectrics, it is misleading to deduce specific

can

values referred to unit cube of the material from the results of tests on sheets. (b) With tin-foil electrodes, the apparent resistance of press-spahn diminishes as the load increases, and it attains a fairly constant value at a load of 400 grams per cm.2. (c) If, with tin-foil electrodes, the load is gradually diminished after a load of 543 grams per cm., the resistance gradually rises, but the rise is less rapid than the diminution in the former case (b). (d) When the full load with tin-foil electrodes is again restored the resistance falls to its minimum value. (e) For small loads, with tin-foil electrodes, the 2nd-minute deflection is in general greater than the 1st-minute deflection. As the load increases, a point is reached at which these deflections become approximately equal. For loads greater than about 360 grams per cm.2, the 1st-minute deflection is in general greater than the 2nd-minute deflection. (f) Increase of voltage, with tin-foil electrodes, especially with small loads, behaves like increase of load, apparently increasing the contact area, and diminishing the observed dielectric resistance. Load, voltage, and the normal effect of " absorption "thus combine to determine the ratio of the 1st-minute deflection to the 2nd-minute deflection. (g) When mercury electrodes are used, the dielectric-resistance, as measured at different voltages, is sensibly the same, even for abrupt and great changes of voltage. (h) When mercury electrodes are used, the 2nd-minute deflection is in general never greater than the 1st-minute deflection. The inference is that when, with tin-foil electrodes, the converse is the case, it arises from imperfect contact, and not from the material itself. (i) When mercury electrodes are used, the dielectricresistance, as measured with a voltage applied in a given direction, is sensibly the same as that measured with the voltage reversed, and this equality appears to become greater after a few reversals. (j) There is a critical load at which tin-foil electrodes yield fairly accurate results. With greater loads there is danger of crushing the material. With a less load the contact is faulty.-The pendulum accelerometer; an instrument for the direct measurement and recording of acceleration: F. Lanchester.-A new form of pyknometer: N. V. Stanford.

Royal Meteorological Society, June 21.-Mr. Richard Bentley, president, in the chair.-Normal electrical phenomena of the atmosphere: G. C. Simpson. In no branch of physics has the discovery of "ions," electrons, and "radio-activity produced a greater revolution than in that devoted to atmospheric electricity. In this paper the author endeavoured to state the chief line along which during the last few years investigations have been made and the conclusions arrived at, and also to point out some of the problems awaiting solution. The amount of radioactive emanation in the lower regions of the atmosphere is increased by all those meteorological conditions which tend to keep the air stagnant over the earth's surface. The meteorological conditions which either cause or often accompany stagnant air are calm, low temperature and high relative humidity, while, on the contrary, high winds, high temperature, and low humidity generally accompany the mixing of large masses of air. This all agrees with the observed facts that the atmospheric radio-activity increases with falling temperature, rising humidity, and increasing wind strength.-Two new meteorological instruments: G. P. Ferguson. The instruments described were (1) automatic polar star light recorder for recording the amount of cloudiness at night; and (2) the ombroscope, an instrument for determining the time and duration of rain. Both these instruments are in use at the Blue Hill Observatory, Mass., U.S.A.

PARIS.

Special

Academy of Sciences, June 19.-M. Troost in the chair. -On the preparation and properties of nitryl fluoride : Henri Moissan and M. Lebeau (see p. 206).-On some alkyl thujones and the combinations of thujone with aromatic aldehydes: A. Haller. The thujone was converted into its sodium derivative by means of sodium amide in ethereal solution, and this acted upon by the alkyl iodide. The preparation and properties of methyl, ethyl, propyl, and allylthujone are described, the special object of the work being to study the influence of the introduction of the alkyl group on the rotatory power. Thujone was also condensed with benzaldehyde, anisaldehyde, and piperonal, the effect in these cases being an enormous increase in the rotatory power. experiments were made to see if in the course of the work the thujone had been converted into isothujone, but this was found not to be the case. An improvement in the method of preparation of isothujone from thujone is also described. Observations on the Giacobini comet (1905 a) made with the large equatorial of the Observatory of Bordeaux Ernest Esclangon. The observations were made on May 2 and 9.-On the influence of concentration on the magnetic properties of solutions of cobalt: P. Vaillant. If A be the coefficient of magnetisation of a solution containing N equivalents of water and n of salt, then A=K'N+Kn, where K and K' are the coefficients characteristic of the water and the salt. It was found that the value of K was nearly independent of the concentration and of the nature of the salt, the chloride, nitrate, and sulphate being studied. The slight variation of K observed would appear to be due to ionisation.-On basic ferric sulphate: A. Recoura. The chemical properties of the anhydrous chloride of neodymium : Camille Matignon. Hydrogen at 1000° C. has no action upon the dry chloride, no trace of a subchloride being detected. Oxygen slowly converts the fused chloride into the oxychloride, NdOCI, water giving rise to the same substance. Hydriodic acid slowly converts the chloride into the iodide, and the bromide is formed with hydrobromic acid by a similar reaction.-On a method for determining the specific heats of solutions. The molecular heat of good and bad electrolytes: P. Th. Muller and C. Fuchs. The liquid is heated by a glass spiral containing mercury through which a constant current is passed, water and the solution being alternately introduced into the calorimeter. The causes of the differences between the specific heats of solutions of electrolytes and non-electrolytes are discussed.-Researches on the mercury formates: Raoul Varet. A thermochemical paper.-On some new nitrodinaphthopyranic derivatives: A. Robyn. On sparteine; the stereoisomerism of the two iodomethylates: Charles

a

Moureu and Amand Valeur. These two iodomethylates cannot be distinguished by their behaviour on heating, as they both split up quantitatively into methyl iodide and sparteine, and hence the author regards the isomerism as of a stereochemical order. The influence of electrolytes on the mutual precipitation of colloids of opposite electrical sign: Larguier des Bancels. On a new form of tartrate of thallium, and on isomorphous mixtures of the tartrates of thallium and potassium: Jean Herbette. Although the tartrates of thallium and potassium belong to different crystalline systems, mixtures of these salts exhibit a true isomorphism; the properties of the mixed crystals of these two salts do not vary in proportion to the chemical composition. A case analogous to this has already been pointed out by Groth for a mixture of potassium chlorate and permanganate.-The action of liquid air on the life of the seed Paul Becquerel. The resistance of seeds to low temperatures depends entirely upon the quantity of water and gas contained in their tissues. If this quantity of water and gas is sufficient, the cold disorganises the protoplasm and nucleus in such a manner that life is impossible, but if the protoplasm has by drying attained its maximum concentration, it completely escapes the action of the low temperature, and the seed preserves its germinating power. -An enemy of the Tonkin coffee plant, the Xylotrechus of the dry bamboo: Louis Boutan.-Researches on the ethnology of the Dravidians. The anthropological relations between the mountain tribes and the castes of the plain Louis Lapicque. On the presence of graptolith schists in the High Atlas of Morocco: Louis Gentil.— On the formation of the Rochefort Cave (Belgium): E. A. Martel. On the evolution of the fossil mammals: Marcellin Boule.

:

A reply to a criticism of M. Depéret.The meteorology of total eclipses of the sun: W. de Fonvielle and Paul Bordé. Remarks on the work done by Sir John Elliot on the lowering of the temperature during the eclipse of the sun.

Number of Strokes of the Brush in a Picture.-F. G. 198
The Hydrometer as a Seismometer.-G. T. Bennett 198
The Pressure of Radiation on a Clear Glass Vane.-
Prof. Gordon F. Hull

The Habits of Testacella.-M. D. Hill
Nature and Man. By Prof. John Perry, F.R.S.
A Life's Work in the Theory of Evolution. (Illus
trated.) By F. A. D.

Dr. William Thomas Blanford, F. R.S. By A. G.
Notes

Our Astronomical Column:

Astronomical Occurrences in July.
New Observatory in Algeria. (Illustrated.)
A Suspected Sudden Change on Jupiter
Brightness of Jupiter's Satellites

198

199

199

200

202

203

207

207

207

207

Elliptical Elements for the Orbit of Comet 1905 a Recent Positions of Eros.

207

207

208

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THE EVOLUTION THEORY.

By AUGUST WEISMANN,

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TRANSLATED BY

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THE BECQUEREL RAYS