Slike strani

in Greece. He is now engaged in preparing a comprehensive memoir on the subject which may be expected to throw new light on some questions of historical geography.

The fanaticism and distrust of the people created constart culties, but Captain Bower, under the pretext of being all hist with a peculiar ritual, succeeded in making observation position openly as part of a religious service, previous ane to do so by stealth having failed.


MR. MACKINDER, in his fifth lecture for the Royal Geographical Society's education scheme, spoke of the chief lines of communication between Asia and Europe and the ways by which successive bands or hordes of Asiatic invaders forced a passage into the heart of Europe. The routes across Asia Minor from the Gate of Cilicia to the northern waters, and the thoroughfare through the Balkan peninsula now traversed by the inter- AN important addition to our knowledge of the che national railway, were shown to have guided the movements of peoples and the formation or dissolution of nations from the dawn of European history on to the present day.

THE United States appears to have entered the field as an aggrandi-ing power, taking up territory beyond the limits of the continent of North America. The annexation of Hawaii seems likely to be effected without remonstrance, and a footing has also been obtained in San Domingo, the eastern part of the island of Haiti.

MR. A. VAUGHAN WILLIAMS has been exploring the region round the mouth of the Sabi River in south-east Africa. has ascended the stream for thirty miles to the limit of influence.

THE orthography of African place names is a perpetual source of confusion. It appears that in place of Zimbabwe or Zimbabye we ought, in order to render the sound of the word used by the people surrounding the ruins, to write " Zimbabghi." The familiar name Mashonaland is in itself a corruption of the native name, but is always pronounced Mashunaland, a pronunciation to which the spelling ought to conform.

nature of this interesting element is contributed by 7 Moraht and Dr. Wischin, of Munich, to the current nam the Zeitschrift für Anorganische Chemie. Two years scarcely elapsed since the position of osmium in the per system was finally decided by the painstaking re-deter of its atomic weight by Prof. Seubert. Previous determ of the atomic weight of osmium had been made with n which Seubert subsequently showed to be impure, and sequence the erroneous value, 1986, had been ascribe! Indeed previous to the year 1878 the order of preceden regards atomic weight of the four metals of the platinan He—gold 196'2, iridium 1967, platinum 1967, and osmin tidal -was entirely at variance with the order demanded by chemical and physical properties, and a standing coats of the periodic law of Newlands and Mendeleef. L year, however, Seubert attacked the case of iridium, and result of a series of determinations, made with the care which has characterised all his work, the atomic we this metal, when obtained in a pure state, was to be 1925, a number very different to that previously to it, and which was afterwards remarkably confirmed, the decimal place, by an independent investigation by Three years later Seubert made his celebrated re-deter of the atomic weight of platinum, which resulted in the s 1943 being finally derived for the true atomic weight confirmed by Halberstadt. In the year 1887 the posi gold was decided by simultaneous independent re-determ of its atomic weight by Thorpe and Laurie in this contyKrüss in Germany, the two values being practically ide 1967. Lastly,' in 1891, Seubert completed his work determining the atomic weight of osmium with a sp the metal of practically perfect purity, with the result old number, 1986, was found to be entirely erroneous, considerable quantities of impurities being present samples previously employed, and that the real vale constant was 190 3, thus removing osmium from its situation at the end of the series and placing it in position at the head of it.

RAILWAYS seem likely at last to become established in China. The line from Teintsin to Taku has now been extended to the River Lan, a total distance of 130 miles, and is

being rapidly pushed northward, a considerable section being perfectly pure metal. This value was likewise suuse already opened for passenger traffic.

CAPTAIN BOWER'S JOURNEY IN TIBET. AT an extra meeting of the Royal Geographical Society, on Monday night, Captain H. Bower described his recent journey with Dr. Thorold across Tibet from west to east. They set out from Leh on June 14, 1891, and were fortunate enough to get well into Tibet before meeting any natives. Travelling due east they crossed a pass of 18,400 feet, on the other side of which lay the Horpa Cho, the highest lake yet met with in Tibet, and probably the highest in the world, its altitude being 17,930 feet. Along the route eastward many other lakes were passed, all salt and without outlet, the want of fresh water being sometimes severely felt; a kettleful of hailstones was a welcome catch on one occasion. The travellers used ponies and donkeys for carrying their loads, as yaks do not eat grain, and grass was often not met with for many days' journey. At length, after travelling east and south-east for about 700 miles, they were stopped within 200 miles of Lhasa by the Tibetans, who paid no attention to Chinese passports, and after much parleying insisted on a complete change of route. The party had to retrace their steps for several days' march, turn northward, and then make their way east at a safer distance from the capital. It was now the month of October and the crossing of passes over 18,000 feet, with temperatures of 15° or more below zero, in strong wind was extremely trying. About the end of November, for the first time for four months, the tents were pitched at a less altitude than 15,000 feet, and soon afterwards Chiamdo was reached. Here great difficulty was experienced with the lamas, who insisted that no European should enter the town; but by the intervention of the Chinese Amban, whose power was really but slight, the party was allowed to proceed, passing round the outside of the town. From Chiamdo to Batang the way was easy, and no difficulties were experienced thereafter. At Ta-Chen-Lu they entered China and reached Shanghai on March 29, 1892. Throughout Central Tibet the authorities disclaimed the sovereignty of China, maintaining that only the grand lama had jurisdiction in that region. Many of the lamas met with were educated and intelligent men, but not inclined to give information. Much difficulty was experienced in getting the names of lakes and mountains, no two Tibetans giving the same answer.

The order of precedence of the metals of the platinum . is therefore as follows :-Osmium 1903, iridium 1925-1 1943, and gold 1967. This order is in full accordan the relative chemical and physical properties of these and the last outstanding exception to the periodic genera has disappeared.

Although the properties of pure metallic osmium, and par ly its atomic weight, are now known with certainty, the of its compounds is yet very little understood. Moreove evident from the result of the investigation of Prof. * that previous workers have been dealing with an impare atomic weight, 1986. It was therefore desirable that B should the chemistry of this element be extended to cos hitherto uninvestigated, but that the composition and pr of the compounds already known should be subjected :


Prof. Moraht and Dr. Wischin have therefore taken study of the compounds of osmium with oxygen, sulpar the halogens, employing material of a very high purity, and the results of their investigation are both m interesting.

Work with osmium compounds is endowed with s personal danger to the chemist, owing to the great far hibited under the most various conditions for the for the tetroxide OsO4, a substance which boils at 100 very volatile at the ordinary temperature, and which a skin, the lungs, and particularly the eyes with most senicsequences.

The material started with was a comparatively pare the best known salt containing osmium, potassium K2OsО4.2H2O. This salt was further purified by

1 nitric acid or aqua regia and absorption of the liberated oxide vapours in a solution of caustic potash. The dark wn solution of potassium perosmate thus formed was largely ted with water, and reduced to osmate by the addition of hol. After the expiration of about twenty-four hours almost whole of the osmium had separated in the form of beautiful e crimson octahedrons of the salt K2OsO4.2H,O, which, after hing with dilute alcohol, proved to be quite free from urity, showing no trace of iridium.

volatile osmium tetroxide, OsO4, but which is quite permanent at the ordinary temperature when preserved under water containing alcohol. It dissolves readily in nitric acid with formation of the hydrate of osmium tetroxide, the so-called per-osmic acid. Cold hydrochloric acid attacks it but very slightly. Upon warming, however, it is entirely soluble, forming an olive-green liquid, which will be subsequently considered, with liberation of a small quantity of chlorine. Sulphuric acid does not attack it. Osmic acid reacts in a most energetic and interesting manner with sulphuretted hydrogen gas. Even in the dry state at the ordinary temperature the reaction proceeds with considerable violence. If the experiment is conducted in a piece of combustion tubing, upon which a bulb has been blown for the reception of the osmic acid, the moment that the gas enters the tube the whole of the black powder immediately becomes incandescent, and drops of water and a large quantity of free sulphur are deposited in the portion of the tube not heated by the reacting substances. The residual product of the reaction is a brown powder, which has been found to be a hydrated oxysulphide of osmium of the composition 20sSO. H2O.

revious observers have noticed that an aqueous solution of ssium osmate, KOSO, is most remarkably affected by sunt, a rapid decomposition being brought about with deposiof a black precipitate to which the composition OsO, 2H,O been ascribed. The specimens experimented with, however, oubtedly contained iridium, and it was therefore of interest vestigate the action of sunlight upon solutions of the pure just described. When the crimson octahedrons of pure SO.2H2O were dissolved in cold water, and the clear redviolet-coloured solution was exposed to direct sunshine, no ence of change was apparent for several days, but the hent the vessel containing the solution was immersed in a of boiling water, while in bright sunshine, decomposition menced, and a black precipitate rapidly accumulated, until the expiration of two or three hours the whole of the um present was deposited. As there is a marked tendency he production of the noxious fumes of osmium tetroxide during decomposition of the hot osmate solution by the waves of it is best to take the precaution of reducing their amount to nimum by the addition of a little alcohol, which acts as a g reducing agent under these circumstances, and by passing ream of hydrogen through the solution during the whole ation. The precipitate is usually so finely divided that conable difficulty is experienced in separating it from the soluThe filtration succeeds best when the filter is previously tened with dilute acetic acid, when a clear colourless filtrate ually at once obtained. The precipitate cannot be dried in rm air bath, as it is largely converted thereby into the ile osmium tetroxide. It may safely, however, be dried phosphoric anhydride in the vacuum of an air-pump. he accurate analysis of an insoluble substance of the nature is precipitate, and containing a metal such as osmium, h so readily oxidises to the volatile tetroxide, is a task of ptional difficulty. The usual method of reduction to metal stream of hydrogen is insufficient, for more or less of the xide is always formed during the process, necessitating the Of the halogen compounds of osmium only the chlorides have of an absorption apparatus containing a solution of caustic.been at all investigated, chiefly by Claus, whose observations

The reaction occurs in accordance with the equation

2H2OsO + 4H,S = 20sSO. H2O + 5H2O + 2S. This oxysulphide of osmium is soluble in acids with decomposition, even sulphuric acid decomposing it with evolution of sulphuretted hydrogen. It possesses acid properties, for it liberates carbon dioxide from carbonate of soda and sulphuretted hydrogen when fused with sulphide of potassium. It would, moreover, appear to contain SH groups, for it yields mercaptan upon treatment with soda and ethyl iodide, the osmium being reduced to the dioxide OsO. Its probable constitution is therefore represented by the graphic formula :

sh, placed in front of the tube containing calcium ide to absorb the water formed. The difficulty is, then, to estimate the small quantity of osmium thus dissolved in arge excess of alkali. It was eventually found that the

electric current from three Daniell's cells precipitates the e of the osmium from such a solution, contained in a nickel which forms the negative electrode, in the form of pure um dioxide, OsO2, which may conveniently be dried in vacuo phosphoric anhydride and weighed as such.

this mode of analysis the interesting fact was eventually ed, that the black insoluble substance formed by the action ht upon a hot solution of potassium osmate is not, as was ously supposed, a hydrate of osmium dioxide of the comion OsO,.2HO, but is no other than free osmic acid itself, ydrate of osmium trioxide, OsO3. H2O or HOsO,. Osmic is thus formed by the direct action of water, under the ince of sunlight and slight rise of temperature, upon the sium salt. This remarkable change is expressed by the le equation:

K2OsO4+2H,O= H2OsO, +2KOH.

e liquid, as soon as the change commences, is observed to it a strong alkaline reaction, becoming, as indicated in the tion, a solution of caustic potash. It is singular that the nce of alcohol and the passage of a current of hydrogen g the reaction do not cause any reduction, serving only to er the further oxidation to the state of tetroxide. Indeed, : crimson octahedral crystals of potassium osmate are covered inshine with warm alcohol and a current of hydrogen is red to bubble through the liquid, no trace of blackening is ved upon the faces of the crystals. The moment water is d, however, decomposition is immediately brought about. mic acid, H2OsO,, is a soot-black powder, which fumes gly in moist air, owing to its rapid conversion into the

/SH Os


When this oxysulphide is warmed in dry sulphuretted hydrogen
another violent reaction occurs, the whole mass again becomes
incandescent, and the whole of the oxygen is eliminated in the
form of water.
sulphuretted hydrogen is pure osmium disulphide OsS2.
The product of this second reaction with
Os,O3(SH)2 + 2H S = 20sS2+ 3H2O.

may be summarised in a few words.

When finely-powdered metallic osmiuin is heated in a stream of dry chlorine sublimates are formed. The first chlorine compound formed is chromous-green in colour, but is only produced to a very slight extent. There is next deposited a dense black sublimate, and finally a smaller quantity of a sublimate of the colour of red lead. None of these three chlorine compounds are crystalline. Claus subsequently stated that the lowest chloride OsCl, is a bluish-black solid when isolated, and forms a dark bluish-violet solution; the sesquichloride Os,Cl, is reddishbrown in the solid state, and gives with water a rose-red coloured solution, and the dichloride OsCl, is the compound which exhibits the colour of red-lead, and yields a lemon-yellow solution

These observations of Claus are completely confirmed by the experiments of Prof. Moraht and Dr. Wischin, who, however, have extended them, and have been able to isolate other and higher chlorides of osmium.


They commenced by warming a large quantity of the free osmic acid above described for two days upon a water-bath with concentrated hydrochloric acid, the flask in which the reaction was conducted being connected with an upright condenser. little alcohol was added in order to prevent the formation of osmium tetroxide. The osmic acid eventually entirely dissolved with formation of the dark olive-green coloured solution previously incidentally mentioned, a little chlorine being evolved at the commencement of the operation. It was found impossible to evaporate the solution upon the water-bath without decomposition, but evaporation in vacuo over sulphuric acid and solid caustic potash, the latter to absorb the hydrochloric acid, succeeded admirably. The solid left after complete evaporation consisted of well formed crystals which assumed the habit of six-sided pyramids. These crystals were dark olive-green in colour when moist, but when the last traces of superfluous water were removed, exhibited a bright vermilion colour. They were readily

soluble in water and alcohol, the solutions being coloured dark green, and the salt may be recrystallised from these solvents. Upon analysis they were found to consist of the chloride Os,Cl crystallised with seven molecules of water.

This chloride of osmium, Os,Cl,.7H,O, would appear to be a molecular compound of the trichloride, OsCl, and the tetrachloride, OsC. For when potassium chloride solution is added to the solution of the crystals in alcohol, a precipitate of brilliant red octahedrons and cubes of potassium osmichloride, K,OsCl, is obtained, showing the presence of osmium tetrachloride, OSCI. Moreover, when the precipitate is separated by filtration, and the filtrate concentrated by evaporation in vacuo, dark green crystals of the trichloride, OsCl,, are deposited containing three molecules of water of crystallisation.

During the reduction of these crystals of the trichloride in a current of hydrogen for the purposes of analysis, a small quantity of a white sublimate was obtained, which probably consisted of the octo-chloride, OsClg, corresponding to the tetroxide OsO. Bromine does not react with osmium with anything like the energy of chlorine. The free elements do not appear to com. bine at all, even at moderately high temperatures. Only a small quantity of a sublimate of a dark brown colour is obtained by passing bromine vapour over osmic acid. This sublimate dissolves to a brown solution in water, which, however, rapidly decomposes with deposition of a black precipitate.

When osmic acid, H,OSO4, is treated with hydrobromic acid in the manner just described in the case of hydrochloric acid a similar reaction occurs with formation of a clear reddish-brown solution which yields, upon evaporation in vacuo over sulphuric acid and solid caustic potash, small crystals of a molecular compound of the tribromide, Os Br3, and the hexabromide, OsBr6, together with six molecules of water of crystallisation. These crystals of Os,Br,.6H,O are dark reddish-brown in colour and exhibit a beautiful metallic lustre. They are quite stable when preserved in a dry atmosphere, but rapidly deliquesce in moist


Iodine appears to possess even less affinity for osmium than bromine. When, however, osmic acid is treated with hydriodic acid a deep greenish-brown solution is obtained which deposits in vacuo dark violet rhombohedrons, exhibiting a brilliant metallic lustre, consisting of the anhydrous tetra-iodide of osmium, OsI. This iodide, the only one containing osmium yet prepared, is permanent in a dry atmosphere at the ordinary temperature, but rapidly deliquesces like the bromide when exposed to moist air.

In relative stability the chloride bromide and iodide of osmium above described exhibit a gradation such as would be expected from the relations between the halogen elements themselves. The iodide is readily dissociated by slightly raising the temperature, and upon the addition of water is decomposed with the deposition of a black precipitate containing the metal. A similar decomposition occurs, although much more slowly, in case of the bromide. The chloride, however, is well-nigh permanent under these conditions, only exhibiting traces of decomposition after the lapse of a considerable time. A. E. TUTTON.

REDUCTION OF TIDAL OBSERVATIONS.1 THE tidal oscillation of the ocean may be represented as the sum of a number of simple harmonic waves which go through their periods approximately once, twice, thrice, four times in a mean solar day. But these simple harmonic waves may be regarded as being rigorously diurnal, semi-diurnal, terdiurnal, and so forth, if the length of the day referred to be adapted to suit the particular wave under consideration. The idea of a series of special scales of time is thus introduced, each time-scale being appropriate to a special tide. For example, the mean interval between successive culminations of the moon is 24h. 50m., and this interval may be described as the mean lunar day. Now there is a series of tides, bearing the initials M1, M2, M3, M4, &c., which go through their periods rigorously once, twice, thrice, four times, &c., in a mean lunar day. The solar tides, S, proceed according to mean solar time, but, be

"On an Apparatus for facilitating the Reduction of Tidal Observations." By G. H. Darwin, F.R S., Plumian Professor and Fellow of Trinity College, Cambridge. A paper read before the Royal Society on December 15, 1892.

sides mean lunar and mean solar times, there are other sp time scales appropriate to the other tides.

The process of reduction consists of the determination of mean height of the water at each of twenty-four special r and subsequent harmonic analysis. The means are taken such periods of time that the influence of all the tides gover by other special times is eliminated.

The process by which the special hourly heights have hither been obtained is the entry of the heights observed at the solar hours in a schedule so arranged that each entry falls in a column appropriate to the nearest special hour. Sche of this kind were prepared by Mr. Roberts for the I Government. The successive rearrangements for each ser special time were made by recopying the whole of the obser tions time after time into a series of appropriate schede The mere clerical labour of this work is enormous, and care is required to avoid mistakes.

All this copying might be avoided if the observed heights we written on movable pieces. But a year of observationg 8760 hourly heights, and the orderly sorting and resoring nearly 9000 pieces of paper or tablets might prove more inter and more treacherous than recopying the figures.

The marshalling of movable pieces might, however, berm to manageable limits if all the twenty-four observations per to a single mean solar day were moved together, for the a able pieces would be at once reduced to 365, and each p might be of a size convenient to handle.

The realization of this plan affords the subject of this pa and it appears that not only is all desirable accuracy atta but that the other requisite of such a scheme is satisfied, an that the whole computing apparatus shall serve any nem times and for any number of places.

The first idea which naturally occurred was to have r sliding tablets which should be thrown into their places number of templates. It is unnecessary to recount all them and failures, but it will suffice to say that the slides an plates would require the precision of a mathematical instr if they are to work satisfactorily, and that the mana would be so expensive as to make the price of the instr prohibitive.

The idea of making the tablets or strips to slide in places was accordingly abandoned, and the strips are short pins on their under sides, so that they can be stuck a drawing board in any desired position. The template were also troublesome to make, are replaced by large she paper with numbered marks on them to show how t are to be set. The guide sheet is laid on a drawing bo the pins on the strips pierce the paper and fix them 2 proper positions.

The strip belonging to each mean solar day is div black lines into 24 equal spaces, intended for the entryhourly heights of water. The strip is nine inches long by. wide, and the divisions ( by ) are of convenient size entries. There was much difficulty in discovering 140 material, but after various trials artificial ivory, or xylon found to serve the purpose. Xylonite is white, will take with Indian ink or pencil, and can easily be cleaned with cloth. It is just as easy to write with liquid Indian ink ordinary ink, which must not be used, because it s surface.

The observations are to be treated in groups of two half lunations or 74 days. A set of strips, therefore, of 74, numbered from o to 73 in small figures on t ends.

If a set be pinned horizontally on a drawing board 10 70 column, we have a form consisting of rows for each mes day, and columns for each hour. The observed heigh water are then written on the strips.

When the twenty-four columns are summed and v the number of entries we obtain the mean solar hory heights. The harmonic analysis of these means gives th solar tides. But for evaluating the other tides the st be rearranged, and to this point we turn our attention

Let us consider a special case, that of mean lunar mean lunar hour is about 1h. 2m. m.s. time; hence the each m.s. day must lie within 31m. m.s. time of a m

I An edition of these computation forms was reprinted by from the Royal Society, and is sold by the Cambridge Scentific Company, but only about a dozen copies now remain.

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The rule for this arrangement is given by marks on a sheet of aper 18 in. broad; these marks consist of parallel numbered eps or zigzags showing where the ends of each strip are to be iced so as to bring the hourly values into their proper places. At the end of a lunation mean solar time has gained a whole y over mean lunar time, and the 12h. solar again agrees with he 12h. Junar. On the guide sheet the zigzag which takes its rigin at the left end of strip o has descended diagonally from ght to left until it has reached the left margin of the paper, and new zigzag has begun on the right margin.

When the strips are pinned out following the zigzags on the heet marked M, the entries are arranged in 48 columns, but he number of entries in each column is different. The 48 inComplete columns may be regarded as 24 complete ones, apperaining to the 24 hours.

Harmonic analysis of the 24 means of the complete columns gives the required tidal constants. It must be remarked, however, hat as the incidence of the entries is not exact in lunar time, nvestigation is made in the paper of the corrections arising out of this inexactness.

The explanation of the guide sheet for lunar time will serve, mulatis mutandis, for all the others.

The zigzags have to be placed so as to bring the columns into exact alignment, and printers' types provide all the accuracy requisite.

To guard against the risk of the computer accidentally using the wrong sheet, the sheets are printed on coloured paper, the sequence of colours being that of the rainbow. The sheets for days o to 73 are all red; those for days 74 to 74+ 73, or 147, are all yellow; those for days 148 to 148 + 73, or 221, are green; those for days 222 to 222 + 73, or 295, are blue; and those for days 296 to 296 + 73, or 369, are violet.

Thus, when the observations for the first 74 days of the year are written on the strips all the sheets will be red; the strips will then be cleaned, and the observations for the second 74 days written in, when all the guide sheets will be yellow, and

so on.

The paper also gives another considerable abridgement of the process of harmonic analysis, which is independent of the method of arrangement just sketched.

In the Indian computation forms the mean solar hourly heights have been found for the whole year, and the observations have been rearranged for the evaluation of certain other tides governed by a time scale which differs but little from the mean solar scale. It is now proposed to break the mean solar heights into sets of 30 days, and to analyse them, and next to harmonically analyse the 12 sets of harmonic constituents for annual and semi-annual inequalities. By this plan the harmonic constants for 11 different tides are obtained by one set of additions. In fact, we now get the annual, semi annual, and solar elliptic tides, which formerly demanded much trouble Some extra computation. A great saving is secured by this alone, and the results are in close agreement with those derived from the old method.

An abridged method of evaluating the tides of long period MS, Mf, Mm, is also given. The method is less accurate than that followed hitherto, but it appears to give fairly good results, and reduces the work to very small dimensions.

The advantages of the method proposed in the present paper may be best realized by a comparison of the amount of work

entailed in the reduction of a year's tides as it has hitherto been carried out by the Indian Survey at Poona, and what it will be under the new method.

It has been usual in the Indian reductions to use three digits in expressing the height of water, and there have been fifteen series, or even more. It follows from a simple multiplication that the computer has had to write 394,000 figures in reducing a year of observation. This does not include the evaluation of the annual and semi-annual tides, so that we may say that there have been about 400,coo figures to write.

It is now proposed to express the heights by two digits, and they only have to be written once, and the number of figures to write is 17,500; accordingly the writing of 382,000 figures is saved.

digits written, say, 394,000 additions of digit to digit. In the old method the computer had to add together all the

It is now proposed to use twenty-four hourly values in three series, viz. S, M, and MS, and twelve two-hourly values in eight others, and the number of additions comes to 123,000. Thus 270,000 additions are saved.

We may say that formerly there were about 800,000 operations (writing and addition), and that in the present method there will be about 140,000. This estimate does not include a saving of several thousands of operations in obtaining the tides of long period. It may therefore be claimed that the work formerly bestowed on one year of observation will now reduce at least five years, and that the results are equally trustworthy.

The manufacture of the computing strips of xylonite is rather expensive, but as it formerly cost in England rather more than £20 to reduce a year of observation, the cost of the apparatus will be covered by the saving in the reduction of a single year, and it will serve for any length of time.

The apparatus, together with computation forms, will be on sale with the Cambridge Scientific Instrument Company at a price of about £8.

It is proper to mention that Dr. Borgen has devised and used a method for attaining the same end as that aimed at in this paper. He has prepared sheets of tracing paper with diagonal lines on them, so arranged that when any sheet is laid on the copy of the observations written in daily rows and hourly columns, the numbers to be summed are found written between a pair of lines. This plan is inexpensive and has considerable advantages, but the chance of error is no doubt increased by the fact that the lines of addition are diagonal, and because figures seen through tracing-paper are comparatively faint.

THE HARVARD COLLEge obserVATORY. THE forty-seventh annual report of the director of the astro

nomical observatory of Harvard College, for the year ending October 31, 1892, by Prof. E. C. Pickering, has been issued. We reprint the following passages:


The number of photographs taken with the eight-inch Draper telescope is 2777. The number taken in Peru with the Bache telescope is nearly two thousand, of which 601 have been received in Cambridge. The examination of these plates has as usual led to the discovery of a large number of interesting objects. variable stars, U Delphini, S Pegasi, T Aquarii, R Crateris, R Carinæ, S Canis Minoris, S Car næ, R Ophiuchi, X Ophiuchi, and Espin's variable star in Auriza in addition to the thirty-seven previously announced have the hydrogen lines bright in their spectra. Seven new variable stars have been discovered this year by means of this property. The number of stars of the fifth type has been increased by eight, making the total number now known of these objects forty-five. The hydrogen line F was shown to be bright in the spectra of six stars in addition to those already known. Photographs have been obtained of the spectra of eight planetary nebule showing bright lines. The spectrum of the nebula surrounding thirty Doradus is unlike that of other gaseous nebulæ. The star A. G. C. 20,937 has a somewhat similar spectrum. Five stars have been shown to have spectra of the fourth type. All of these peculiarities have been detected by Mrs. Fleming except in the cases of one of the known variables, one of the planetary nebula, and two of the stars of the fourth type, which were found by Mr. A. E. Douglass, in Peru, before the plates were sent to Cambridge.

The amount of valuable material accumulated with these instruments is continually increasing, and has proved useful in many cases in studying the history of newly-discovered objects.

The brightness for several years past of stars suspected of variability has been furnished to various astronomers. Plates have been sent to the Lick and Amherst Observatories and to the Smithsonian Institution for special investigations. From one of them a new variable star in Aries was discovered by Prof. Schaeberle. It is hoped that this use of our plates may increase in the future. A large number of photographs were taken of the new star in Auriga. An examination of the older photo graphs showed that the region containing it had been photo. graphe eighteen times from November 3, 1885, to November 2, 1891, and that it was then apparently fainter than the thirteenth magnitude. It appeared upon five plates taken between December 16, 1891, and January 31, 1892. After its discovery it was photographed on sixty-five chart plates and thirty-six spectrum plates, until April 6, when it became too faint to be visible in the encroaching twilight. All of these plates have been carefully studied and measured. Twenty-one charts and fifteen spectrum plates of this object have been taken since its reappearance in September, 1892. On these last plates, the spectrum is shown to resemble that of a planetary nebula.

Many photographs of the lunar eclipse of November 15, 1891, were taken both at Cambridge and at the Boyden observing station near Arequipa, Peru. The examination of these photographs for the detection of a possible lunar satellite led only to a negative result.


The number of photographs taken with the 11-inch Draper telescope is 996. They include 372 spectra of 8 Auriga to determine the law of periodic doubling of the lines. of these images show the lines double so that the separation can be measured. In like manner 208 spectra of Ursæ Majoris have been photographed, and in 49 of them the lines are separated widely enough to be measured. A similar study has been made of the new star in Auriga, of B Lyræ, of 11 Monocerotis, and of some other stars having peculiar spectra. Photographic charts have also been obtained of numerous variable stars, stars having large proper motion, clusters and stars having peculiar spectra to determine their parallax if it is perceptible.


In establishing the fund that bears his name, Mr. Boyden desired to secure an astronomical station where the effects due to the atmosphere would be greatly diminished. This has now been successfully accomplished in the Harvard Station at Arequipa, Peru, where the effect of the air is no longer as heretofore the principal obstacle to progress in astronomy. Instead of this the limit is now the size and excellence of our instruments. A great advance would probably be made in our knowledge of the planets, and perhaps of the fixed stars, if a telescope of the largest size could be mounted under such favourable conditions.

This station has continued in charge of Prof. W. H. Pickering. The instruments chiefly employed have been the 13-inch telescope, the 8-inch Bache telescope, and a photographic camera having an aperture of 24 inches. The first of these instruments has been largely devoted to visual work, for which unusual advantages are afforded by the transparency and steadiness of the air at this station. Many interesting results have been derived from the observations made of the moon and various planets. The observations of the moon relate to Plato and other regions, which have been carefully examined, and also to the systems of bright streaks visible at full moon. The markings of Mercury have been studied, and this investigation appears to confirm Schiaparelli's view that the rotation of Mercury on its axis occupies the same time as its revolution in its orbit. Although this planet appears to have no atmosphere, the markings upon it are very faint compared with those upon the moon. Venus was micrometrically studied near its inferior conjunction with regard to its diameter, polar compression, and the refractive effect of its atmosphere. No permanent markings could be detected. An extensive series of observations was made upon Mars. The relative positions of 92 points upon its surface were determined by the micrometer. More than forty minute black points were discovered, provisionally designated as lakes. The polar compression of the planet was measured, and appeared to be greater than that indicated by theory, which may be due to an excess of cloud in the equatorial regions. The presence of the dark and narrow streaks called canals by Schiaparelli has been confirmed and various measurements of them have been made. The clouds projecting beyond the limb, and terminator, discovered at

the Lick Observatory, have been studied, and their heigh been found to be at least twenty miles. The relative cover different portions of the planet have been minutely cher Two large dark blue areas have been detected, and other tions have been noticed to be subject to gradual change colour.

Many new double stars were found in a survey of heavens south of 30°, between 12h. and 18h. The As occultation of Jupiter was observed both visually and ph graphically, as was also the new star in Auriga and comet, the photographs of which showed detail not notice the visual observations.

With the camera, having the aperture 23 inches, very s factory photographs have been obtained of the Mag clouds, showing their composition to be partly of 5. partly of nebulous matter; also the spiral structure of the larg of the two clouds.

Meteorological observations are regularly carried on. S: have been established at Mollendo, 100 feet above seale La Joya, the elevation of which is 4,150 feet, at the ch station, 8,060 feet high, at the Chachani Ravine 16,5high, where numerous miscellaneous observations have made. Notwithstanding the great height of the last station, it can be reached by a mule path, and a hut hasi zi erected where the observers can pass the night. A the Arequipa valley and neighbouring mountain h made, depending on two separate base lines. The hegt the mountains have been measured, and in some case result has been checked by a mercurial barometer.

THE BRUCE PHOTOGRAPHIC TELESCOPE This instrument, which if successful will be in many re the most powerful in the world, is now rapidly appr completion. The eight surfaces of its objective hav ground and polished so that it could be tested on a sat results were satisfactory, although, of course, no opinion can be formed until the final corrections are a The focal length proved to be that desired within has per cent. Plans have been made and the foundations la one-story brick building with a sliding roof, in which it erected during its trial in Cambridge. After this it is to send it to the Arequipa station in Peru.

Photographs have been taken with the transit ph on 192 evenings, and when clear, throughout the eares With this instrument images are obtained of all starts than the sixth magnitude which cross the meridian de night. The value of this work was illustrated when star in Auriga was discovered in February, 1892. I peared that this object had been photographed on twe since December 10, 1891, while no trace of it was to thirteen plates covering this region and taken before Dece 1891. The only knowledge that exists of its charge during the six weeks in which it remained undiscover nished by these photographs and those taken with 2 telescopes. It was also photographed with the tra meter on twelve nights after its discovery. Of the sand standard stars of the tenth magnitude about eigh have been selected by Miss E. F. Leland during the p-" making eleven thousand in all.


OXFORD. In the Chemical Department Prof. lecturing on the glucoses, Mr. Fisher on inorganic c Dr. Watts on organic chemistry, and Mr. Veley chemistry. There are about sixty students work laboratories, and a few of the senior men are eng search.

Among the apparatus belonging to the late Duke borough, presented by the Duchess, are three large scopes by Hilger, one having five prisms, another bei vision spectroscope 5 feet 6 inches in length, two b Deleuil; a mercury pump by Alvergniat, Dumas' vap apparatus, Thomson's electrometer gramme mac Khumkorf coil and a quantity of valuable glass apparata. are besides a number of specimens of comput) earths.

The Regius Professor of Medicine has placed his pa

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