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the Thames." A mile to the west at Highbury, other molluscan genera are represented. A list of the Highbury shells is given by Dr. John Evans-"Stone Implements," P. 524.

I now come to the bed of gravel indicated at B (Fig. 1) and A (Fig. 4). It is found at an average depth of 12 feet, and descends to 20 or 30 feet from the surface; this drift contains, chiefly in its upper parts, lustrous sub-abraded Palæolithic implements of medium age. All these tools have been more or less moved and relaid by the agency of water; none are quite unabraded; bones, teeth, and tusks of the mammoth also occur, with other mammalian remains, driftwood, &c. This deposit has been described by Prof. Prestwich in the Quarterly Journal of the Geological Society, 1855, vol. xi. p. 107. The material is remarkable for containing immense blocks of sandstone, probably never moved by water alone, and sometimes weighing one, two, or more hundredweights; that these stones fell from blocks of drifting ice seems extremely probable. Some of them measure two feet across, and they must have been brought from the north long prior to the deposition of the trail, and probably long after the time when other immense blocks found at 20 feet and 30 feet at the bottom of the gravel were deposited. Some show glacial striæ. Generally in the deepest pits, the third and oldest class of implements is found, the examples are rudely made, massive, deeply ochreous in colour, with a thick ochreous crust, the ochreous tint not derived from the matrix they are now in; they are generally very much abraded, indicating transport from a long distance, or long dashing about in water with other stones, but as the three different classes of implements will be illustrated in my concluding note, and proved to be of totally distinct ages, far removed from each other, I need not refer to them at length here.

It commonly happens, that the higher the gravels above the present rivers, the older they are, but here we have an instance where the newer gravels and more recent implements are from 8 feet to 26 feet higher than the old. WORTHINGTON G. SMITH

THE

THE COMET

HE Astronomer-Royal has received, through Sir James Anderson, a telegram from Mr. Gill, in the following terms:-"Please inform Astronomer-Royal that comet's declination in my letter of September 11 should be 56 minutes 30 seconds south. Sudden disappearance of comet at ingress on sun's disc observed September 17 days 4 hours 50 minutes 58 seconds Cape mean time. Comet not visible on sun." Mr. Gill's remarkable observation is without a precedent, and an extraordinary illustration of the intense brilliancy which the comet attained at perihelion.

last micrometrical difference of declination into arc: one revolution = 53"1. He states that he made an immediate attempt to telegraph to Greenwich and Dun Echt, but the office at Ealing was unfortunately closed.

We have received several drawings from M. Bulard, of Algiers, showing the appearance of the comet as viewed with the naked eye, in one of which the tail is depicted with considerable curvature. Also a sketch of the head as seen in a powerful telescope, exhibiting the system of envelopes rising from the nucleus, which has characterised several recent bright comets (see Figure).

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The following elements of this comet have been calculated by Mr. Hind from the Dun Echt and Coimbra meridian observations on September 18, a meridian observation at the U.S. Naval Observatory, Washington, on September 21, and an observation made at the Collegio Romano, at Rome, on the morning of October 2, obligingly communicated by Prof. Millosevich:

Perihelion passage, September 17:2169, Greenwich M.T. Longitude of perihelion 276 14 36) Apparent 346 6 58 equinox

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Inclination

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ascending node

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The Emperor of Brazil telegraphs thus to the Academy of Sciences of Paris:-" Rio, 26 Septembre, 10h. 20m. Note Cruls. Grande comète australe visible de jour Logarithm of perihelion distance observée aujourd'hui. Queue 30°. Présence sodium et carbone. 25 Septembre.-Visible de jour au sud de Rio 18, 19, 20. Vue par moi aujourd'hui de 4h. 10m. à 5h. 40m. matin. Splendide 26."

Value.

Mr. Ainslie Common, of Ealing, whose daylight observations on September 17 may have an important bearing on the theory of the comet, has furnished us with the following extract from his note-book on that date :"10.45. Found bright comet. S. W. sun. 10.59. Comet precedes sun, 6m. 5 s., centre to centre 11. 10. Comet south, sun's limb, 20R 50D 18' 8"... 11.47. Comet precedes sun, 5m. 48s. (?) 11.58. Comet south, sun's limb, 16R 60D = 14' 41". 12.0. Comet precedes sun, 5m. 44s. (good) 12.6. Comet south, sun's limb, 15R 55D = 13′ 45′′. Clouds came over shortly after this."

=

3

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3

Mr. Common has corrected an error in reducing the

...

Motion-retrograde.

37 58 59 Sept. 25. 7'906527

These elements afford further indication of disturbance of the comet's motion near the time of passage through perihelion. At the moment when Mr. Gill observed the sun's centre was consequently 16'0, the orbit gives the comet upon the sun's limb, when the distance from the central distance, as 109, or the comet projected upon the sun's disc. Considering that Mr. Gill's observation was made less than one day previous to the accordant meridian observations at Dun Echt and Coimbra, it is not easy to see how such difference could arise from error of elements, which represent the middle position employed in their determination within a minute of arc.

The following expressions for the comet's heliocentric co-ordinates x, y, z, referred to the equator, are to be used in connection with the X, Y, Z of the Nautical Almanac, in the calculation of geocentric positions :

x = r. [9'99521]. sin (v + 9 6·2)
y = r. [9'98774]. sin (v + 277 24)
2 = r. [9'44252]. sin (v + 130 17:5)

r being the radius-vector, and v the true anomaly.

[Mr. Gill writes on September 19: "Yesterday and today the comet is a brilliant daylight object, and was observed on the meridian by myself with the Transit Circle. We have a whole lot of Alt-Azimuth observations which will be reduced as soon as possible. They were the only kind of observations possible, as the comet was only visible by glimpses through holes in the cloud between September 8 and perihelion."

In a letter addressed on the same day to the Astronomer Royal (with a copy of which he has favoured us) Mr. Gill says: "On Sunday, the 17th inst., the comet was followed by two observers with separate instruments right up to the sun's limb, where it suddenly disappeared at 4h. 50m. 58s. Cape M.T."]

NOTES

PROBABLY some of our readers may have heard that Mr. W. Spottiswoode met with an accident recently. The fact is that on September 30 last he broke his left humerus within the capsule, through the overturning of the tricycle he was riding. He has, we are glad to learn, been carefully attended, and is getting on as well as possible.

A PRIVATE letter to this country conveys the intelligence of the death, on September 11, at Kandy, of Dr. Thwaites, F. R.S., for many years director of the Royal Botanic Gardens, Peeadeniya, Ceylon. We shall defer to a future issue some particulars

of his life.

THE death is announced, at the early age of forty-eight years, of the well-known scientific photographer, Dr. D. Van Monck

hoven.

WE are glad to learn that a memorial signed by Professors Paget, Humphry, Hughes, Newton, and Moseley, Drs. Michael Foster and S. H. Vines, and Messrs. G. H. Darwin, E. W. Blore, Coutts Trotter, A. Sedgwick, and J. W. Clark, was presented to the Vice-Chancellor of Cambridge University (Dr. Porter) on the 4th inst., representing the desirability of esta blishing some memorial of the late Prof. Balfour in the University. The Vice-Chancellor, in accordance with this request, has called a meeting of Members of the Senate and others for October 21, at 4.30 p.m., in the Lecture-Room of Comparative Anatomy, in the New Museums, "to take steps to establish in the University a memorial of the late Prof. Balfour."

original meter and kilogramme deposited in the Archives, with the new standards. The difference had been proved to be o‘000006:n. for the meter, and 0'00001 gram for the kilogramme. The consequence is that a slight correction will be required for the measures taken with the international meter as the comparison between two measures of length can be executed with a precision of one part in ten millions. The new international kilogramme can be used without any correction at all.

next.

Two International Conferences will open in Paris on Monday One of these is for the object of settling upon a plan for the protection of sub-marine telegraph cables; the other is to establish throughout Europe the important desideratum of technical uniformity in relation to electricity. England, France, Germany, Austria, the United States, Spain, Denmark, Norway, and Sweden will be represented.

M. GABRIEL DE MORTILLET, Professor of Archæology to the School of Anthropology of Paris, has just published through Reinwald a work under the title of "Le Prehistorique,” which may be considered as the first complete manual for the study of the Archæological Museum of St. Germain. M. Gabriel de Mortillet has been attached to this establishment from its foundation by Napoleon III. up to the present time, and is industriou ly engaged in its completion. The author, who is one of the few living geologists who investigated the formation of glaciers in Switzerland with Agassiz, attempts at the end of his volume to determine how far distant is the epoch when Homo Sapiens made his first appearance on the earth, by estimating the rate of progression of blocks which were carried by former ice-fields, and he comes to the conclusion that the space of time that has elapsed since that event took place exceeds 200,000 years.

THE meteorological station on the summit of the Säntis has recently been opened, and this latest Swiss station promises to be of importance with regard to the progress of meteorological science. In its altitude of 2504 metres it is surpassed only by the observatories on the Stelviɔ (2548 metres), the Pic du Midi in the Pyrenees (2877 metres), and the station upon the Colorado Peak (4340 metres).

THE Panama Star and Herald of September 14 gives details of several earthquake shocks which had visited the isthmu during the preceding week, doing much damage, but, fortunately, only causing two deaths. At 3.20 a. m. on Thursday, the 7th, the inhabitants were aroused from their beds by one of the longest and most severe earthquake shocks ever experienced in the city. It was preceded by a hollow, rumbling noise. The motion was wave-like, and proceeded almost directly from north to south. The first and most severe shock must have lasted at least 30 seconds. Extreme damage was done to buildings. A second and milder shock occurred about half an hour after the first. The Pacific Mail steamship Clyde, arriving from San

SOME forty eminent German botanists met at Eisenach on September 16, under the presidency of Profe sors Pringsheim, Cramer, and Willkomm, and founded a German Botanical Society. The new society has its seat at Berlin, and its object | Francisco, reported that the earthquake was severely felt on is to form an effective and supporting centre for all efforts in the domain of scientific botany in Germany.

As is well known, the French Institute is divided into five classes, which meet together once every year. The president of this reunion is chosen in rotation from among the president of each of the five sections. The chair will be occupied this year by the president of the Academy of Sciences, who is styled director, and who happens to be M. Dumas, one of the two perpetual secretaries of the Academy of Sciences. M. Dumas will

deliver on this occasion an address which it is stated will be of special importance. This meeting will take place on October 25 next.

M. DUMAS delivered at the sitting of the Academy of Sciences of October 9 an address summarising the works of the International Commission of Weights and Measures. He stated that the commissioners had executed a comparison between the

board. Passengers declared that it appeared as if the vessel were lifted bodily from the sea and allowed to fall back. The effects of the earthquake along the railroad were most marked. The stone abutments of several of the bridges were cracked and almost split, and the earthworks sank in half a dozen places. In several places where the direct action of the shock appears to have made itself most strongly felt, the rails were curved as if they had been intentionally bent. The severe shock on the morning of the 7th was followed during the day by several others of less intensity, and at 11.30 p.m. a sharp shock alarmed the whole city, and drove the people from their houses to the squares. Another slighter shock occurred at about three in the morning; but, fortunately, neither it nor its predecessor added further ruin to that already incurred in the city. All the shocks were felt on the islands in the bay, and some houses suffered at Taboga. On the morning of the 7th, at about 3.15, the residents of Colon

were aroused by the earthquake shock which has caused so much alarm and damage to the whole isthmus. The duration of the shock was fully 60 seconds, and was so severe that the whole populace rushed into the streets as rapidly as their feet could carry them. About half an hour afterwards another shock was felt, but much lighter than the first. A deep fissure was opened in the earth from the south end of the freight-house for a distance of about 400 feet along the walk leading in the direction of the ice-houses. Many buildings were moved slightly from their foundations, but on the whole remarkably little damage was done. On board the vessels in the harbour the shock was also felt very severely. About I p.m. another much slighter shock was felt, and during the succeeding night two more slight disturbances were reported. It may be of meteorological interest to observe that the sea at the time remained calm, the atmosphere quite clear, and the stars and waning moon remarkably brilliant. Soon after, say about 4 o'clock, a slight fog wafted from inland; no rain fell. All day an ominous calm prevailed without rain, with fluctuating barometer and excessive heat. Another slight shock occurred at Panama on the morning of the 9th, a little before 5 o'clock, but fortunately no damage was done. The same shock was lightly felt in Colon and along the railroad track. All day on Saturday no shock was felt, and the night passed quietly. At mid-day on Saturday, there was a marked change in the atmosphere, and, with a refreshing shower which fell, the murky, sultry air of the previous days entirely disappeared. The rumours of a volcanic eruption at Chagres are entirely without foundation. The earthquake was felt there, did some little damage, and opened a few cracks in the ground. The earthquake of the 7th was felt at the Pearl Islands, in the bay. At Donoso, Govea, and Rio Indio a number of shocks were felt, and the people were much frightened. At Miguel la Borda, 35 miles from Colon, in the direction of Bocas del Toro, the tide rose to an unusual height and flooded some of the houses, which are built on the beach almost on a level with the sea. The earth sank in about a dozen places. The Governor of the district writes officially that several boiling springs suddenly appeared, some of which throw hot water to a considerable height. Letters have been received from the towns of La Villa, Chitré, Macaracas, ann Natà, all in the State, announcing that several shocks have been felt, but that the material of which the houses are built-bamboos and adobes-resisted the movements, and they suffered no damage. Two or three slight tremblings were experienced in Panama during the night of the 12th, but they caused no alarm, and many people were returning to their houses.

IN the Photographic Exhibition, which was opened in Pall Mall on Monday, there are several pictures of more than artistic interest. We may mention especially Captain Abney's views taken on the Alps, and showing the great difference in the photographic quality of the light reflected from the sky at high altitudes (9,000 to 10,000 feet), and that reflected at lower levels. Mr. Grant's photographs taken on board Mr. Leigh Smith's yacht Eira during her cruise to Franz Josef Land in 1880, are also of interest, as is also Mr. Shadbolt's photograph taken from the car of a balloon at the height of 2,000 feet, showing the streets and houses below.

THE Council of the Statistical Society have again decided to grant the sum of 20%. to the writer who may gain the "Howard Medal" in 1883. The subject is—“The best exposition of the experiences and opinions of John Howard on the preservation and improvement of the health of the inmates of schools, prisons, workhouses, hospitals, and other public institutions, as far as health is affected by structural arrangements relating to supplies of air and water, drainage, &c." Candidates are referred to the text and foot-notes of Howard's two works on "Prisons" and "Lazarettos."

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BOTANISTS will learn with satisfaction that the Cavaliere d'Amico has succeeded, not without considerable difficulty, in acclimatising a number of foreign plants in Sicily. They are being exhibited at the present moment at the Agricultural Exhibition of Messina, and excite a great deal of interest among the spectators. Amongst them are the tea plant, Persea gratissima, Cinchona succirubra, Indigofera tinctoria, and Myrica cerifera. Cav. d'Amico intends to establish a tea plantation of some extent not far from Messina, and it is hoped that Sicilian tea may in a few years become an important article of commerce.

IN a vineyard at Bonn, Phylloxera have recently made their appearance. The necessary precautions were at once taken.

THE eminent Berlin sculptor, Herr Pohle, is now about to complete a bust of the celebrated geographer, Karl Ritter, for the Geographical Society of Berlin.

PROF. SIMON NEWCOMB, of Washington; Lieut. T. L. Casy, United States Army; Ensign J. H. L. Holcombe, United States Navy; and Mr. Julius Ulke, forming the expedition despatched by the Government of the United States to observe the transit of Venus at the Cape, left Plymouth last Friday in the Union Steamship Company's mail steamer Durban. Miss Newcomb, daughter of the Professor, the lady member of the expedition, is in London, the epidemic of smallpox at the Cape deterring her from proceeding with her father. Mr. Gill, the Astronomer Royal at the Cape, has expressed his willingness to render the members of the expedition every facility as to the selection of a station by collecting information. It is probable that Beaufort, which is 300 miles from Cape Town, will be chosen, from the fact that in that district there is proverbially a clear sky.

THE Danish astronomers, who have been selected to take observations of the transit of Venus, have left Copenhagen for Santa Cruz.

ON commencing his Winter course of lectures on Comparative Anatomy at King's College, Prof. Jeffery Bell made the following remarks:-"In ordinary circumstances it is well to proceed at once to the work before us, but, during the six months that have elapsed, since I last addressed a class of comparative anatomy from this chair, two heavy blows have fallen on the students of zoological science; the two most remarkable of English workers have been taken away from us, the one full of years and honours, the other the bearer of a glorious promise. I should not be doing my duty if I were not to ask you to pause for a moment on the threshold of your studies to bear witness with me to the regrets which we justly feel at the death of Charles Darwin, and the sense of irreparable loss which is connected with the name of F. M. Balfour. The father of modern zoology, the reformer of all our conceptions as to the workings of nature in the organic world, the assiduous and patient collector of the facts of natural history, the prince of observers and the leader of philosophical natnralists was carried to his grave in our national burying place amid the mourning of tthe whole civilised world; the broad outline of his work is well known to you all. On the treacherous slopes of an ice-bound mountain, away from kindred and friends, save such as his character had won for himself in an Alpine village, and yet always in the minds of those who knew him, Francis Balfour in, as we may be assured a moment of time, yielded up a life of which only thirty years had been spent, and lost to science and society what had promised to be as many years and more of patient and far-seeing investigation, free from prejudice, animated by the most scientific and philosophical of ideas while he himself, urged on by the success of the past, would have sought only fresh fields of victory in the future. It would be useless to point out in detail here, where so many are only beginners, the special services of Prof. Balfour, but you will note that his name will be constantly quoted during this course,

as the discoverer of facts which have often thrown unexpected light on the problems of our science, and have always, at least, been of the highest importance, and stated with admirable truth and modesty.'

THE Annales de Chimie et de Physique reproduces in its August number a paper relating to the theory of dissipation of energy, read by Macquorn Rankine at the British Association meeting in 1852.

A SERIES of scientific ascents were made on Sunday afternoon from the Place Saint Jacques, in Paris, under the auspices of the Académie d'Aérostation Météorologique. At a height of eight hundred feet photographs of the entire horizon were taken by means of a panoramic apparatus invented by M. Triboulet. In a brief explanation of this, given by one of the members of the Academy, it was pointed out that the experiment was as important from a military as from a scientific point of view, since it would enable an army to ascertain exactly the number and position of their enemies. At another ascent telephonic conversation with persons on the ground was carried on at the height of five hundred feet. The experiments were under the auspices of the Municipal Council of Paris.

THE aurora borealis which was seen in so many parts of England on October 2, was also visible in France from a very large number of places.

M. DUVAUX, the French Minister of Public Instruction, has opened the first superior school for females established in France. It is situated in the city of Rouen, and the regular course of study will begin this year. Many similar establishments are in course of construction in several parts of the country.

THE additions to the Zoological Society's Gardens during the past week include a Sykes's Monkey (Cercopithecus albigularis ? ) from East Africa, presented by Capt. F. W. Schwedler; a Binturong (Arctictis binturong) from Malacca; a Common Fox (Canis vulpes), British, presented by Mrs. Studholme Brownrigg; two Goshawks (Astur palumbarius) from Germany, presented by Dr. Rudolph Blasius, C.M.Z.S.; a Common Raven (Corvux corax), two Lesser Black-backed Gulls (Larus fuscus) from Scotland, presented by Mr. F. G. Bury; two Greater Sulphur-crested Cockatoos (Cacatua galerita) from Australia, presented by Mr. C. Kerry Nicholls, F.Z.S.; a Puff Adder (Vipera arietans) from South Africa, presented by Lieut. R. Crawshay; an Ornamented Lorikeet (Trichoglossus ornatus) from Moluccas, a Crested Curassow (Crax a'ector) from Guiana, two Illiger's Macaws (Ara maracana) from Brazil, purchased; two Brazilian Hangnests (Icterus jamaicai) from Brazil, deposited; an Australian Fruit Bat (Pteropus poliocephalus), born in the Gardens.

CHEMICAL NOTES

AN exceedingly ingenious patent for the manufacture of hydrogen and oxygen has been taken out by M. N. A. Hélouis, of Paris. Wood charcoal is obtained by heating wood in closed vessels: the gas which is evolved is u ed for heating the retorts in which hydrogen and oxygen are produced, the tar is used for carburetting hydrogen, the pyroligneous acid is employed to decompose sodium sulphite (produced in another stage of the process), whereby sulphurous acid and sodium acetate are obtained. By passing steam over hot wood charcoal, a mixture of hydrogen, carbon monoxide, and dioxide is obtained; the mixed gases are passed into retorts containing heated gypsum, which is reduced by carbon monoxide to calcium sulphide; the escaping carbon monoxide is absorbed by soda solution, giving sodium bicarbonate. Oxygen is obtained by decomposing gypsun (600 parts) by silica (340 parts river sand); the mixture of sulphur dioxide and oxygen which is produced, is passed into caustic soda solution, whereby sodium bisulphite is formed; the residual sulphur dioxide is absorbed by milk of lime. The calcium sulphite produced by the final washing of the mixed gases is decomposed by sodium bicarbonate, giving calcium carbonate

and sodium bisulphite; the latter is decomposed, as already described, by pyroligneous acid, and the sulphurous acid produced is oxidised to sulphuric acid in a cylinder containing platinised pumice-stone, by air containing 75 per cent. of oxygen. The calcium sulphide which remains in the oxygen retorts is decomposed by carbon dioxide and steam; the sulphurected hydrogen produced, after being freed from moisture by passing through a condensing apparatus, is burned with air rich in oxygen, and the sulphurous acid formed is conducted into the leaden chambers of the sulphuric acid manufactory. Air containing 75 per cent. oxygen is obtained by pumping air into a cylinder containing a mixture of 80 parts water and 20 parts glycerine; when the pressure has reached 10 atmospheres, communication is made between the first cylinder and another from which air has been removed; air rich in nitrogen remains in the first cylinder. By repeating this operation, a mixture of 75 per cent. oxygen and 25 per cent. nitrogen can be obtained. Another method of obtaining nearly pure oxygen from air consists in passing the latter into an iron cylinder containing a bag of silk covered with caoutchouc; the dialysed air is then driven by a steam jet into a condenser, and thence passes into a second similar cylinder; this process is repeated several times; a mixture of 98 per cent. oxygen and 3 per cent. nitrogen may thus be obtained, but for most metallurgical or lighting purposes a mixture containing 60 per cent. oxygen is sufficient. Nitrogen escapes from each iron cylinder by a side tube which dips under water. The silk bags used for dialysing air are prepared by washing ordinary caoutchouc with a mixture of carbon disulphide and alcohol (whereby substances are removed which would readily stop the pores of the caoutchouc-covered silk) making into a paste with benzene, and placing a layer of this between two layers of silk.

IN the Scientific Proceedings of the Ohio Mechanics' Institute (1. 35) a process is described for melting iridium by heating in a Hessian crucible with phosphorus, and subsequent renewal of the phosphorus by repeated fusion with lime. The metal, in very thin sheets, can be cut by a copper wheel making 2000 revolutions per minute, and having its surface covered with emery, or corundum, and oil. Metallic iridium is nearly as hard as ruby; no steel tools make any impression on it; attempts have been made, with fair success, to use it in place of carbon as the negative pole in the electric are light.

It is stated in the Chemical Review that recent analyses of the water from the Holy Well at Mecca, which is so eagerly drunk by pilgrims, show this water to be sewage, about ten times stronger than average London sewage.

ARTIFICIAL ivory of a pure white colour, and very durable has recently been manufactured by the inventor of celluloid: it is prepared by dissolving shellac in ammonia, mixing the solution with oxide of zinc, driving off ammonia by heating, powdering, and strongly compressing in moulds.

ON THE ALTERATIONS IN THE DIMENSIONS OF THE MAGNETIC METALS BY THE ACT OF MAGNETISATION1

DR. JOULE long since discovered that when a bar of iron was magnetised by an electric current, an elongation of the bar took place. In subsequent experiments, published in 1847, Joule found that the elongation amounted to about 1-200,000th of the length of the bar for the maximum magnetisation, and that the total elongation was nearly proportional to the square of the actual magnetisation. By placing the bar in a vessel of water stopped with a capillary tube, it was found that the volume of the iron did not augment, and hence Joule concluded that the sectional area diminished in proportion to the elongation. Under longitudinal tension, magnetisation caused a shortening of the rod when the tension exceeded 600 lbs. for a rod a quarter of an inch square. Soft steel behaved like iron; but hard steel, under all circumstances, Joule found to shorten slightly when the magnetising current passed

In 1873 Prof. Mayer repeated Joule's experiments with new and delicate apparatus; the elongation of the iron he found to amount to 1-277,000th of its length for the maximum magnetisation. Mayer also found that soft as well as hard steel contracted under magnetisation.

1 Paper read at the Southampton Meeting of the British Association by Prof. W. F. Barrett, F.R.S.E., Professor of Physics in the Royal College of Science, Dublin.

In the same year I made a series of experiments on the other magnetic metal, nickel and cobalt, and found that whilst cobalt lengthened under magnetisation, nickel appeared to suffer no change. This result is surprising, for nickel more nearly resembles iron and cobalt than steel in magnetic properties, the formen having little coercive force, and the latter very considerable retentive power. With entirely new apparatus the experiments were repeated, and a distinct shortening of the nickel was now found, cobalt elongating but not so much as iron. This observation is, I believe, new, the fact was first noticed by me on September 9, 1873, but some uncertainty as to the reliability of the apparatus I then used led me to put the matter aside till July, 1876, when the experiments were repeated, and the fact that cobalt elongates and nickel retracts under magnetisation, was fully confirmed.

The multiplying apparatus that was found to yield most satisfactory results was a simple form of optical lever, a mirror vertically fixed over the fulcrum of a lever of the first order, and reflecting a scale at some distance into an observing telescope. The apparatus will be more fully described in the report that will be presented next year; a committee, with a small money grant, having been appointed at a previous meeting of the Association to investigate this and certain other molecular changes accompanying the magnetisation of iron, described by the author at the Bradford meeting of the Association.

The results so far obtained may be summed up as follows:However often the current traverses the helix around the bar of cobalt, the elongation is practically the same after the first current, and amounts to about two-thirds of the elongation produced in an iron bar of the same dimensions. In my measure. ment the elongation of the iron amounted to about 1-260,000th of its length for the maximum magnetisation; the iron elongated 5 scale divisions, and the cobalt 3, or 1-425,000th of its length. With nickel, the retraction on the same scale was 10, or twice the elongation of the iron, or about 1-130,000th of the length of the bar. Reversing the current made no alteration in the results. The index returned promptly to zero on the cessation of the current. The retraction of the nickel was so instantaneous that it was only by noting the scale-reading that any motion could be discovered to have taken place. The helix in all cases was the whole length of the bars.

Inclosing the bars in a vessel of water terminating in a capillary tube (the stem of a mercurial thermometer of extremely fine bore), and surrounding the vessel by a powerful magnetising helix, no motion of the water-level in the capillary tube was noticed with iron and cobalt on the making, breaking, or reversing the current in the helix; with nickel no motion was observed on making, and a barely perceptible, but still definite, fall of the index, equal to about 1-10,000,000th of the volume of the bar, occurred on breaking, which was more clearly seen by frequent interruptions of the current.

The "magnetic tick" is heard loudly with cobalt and nickel, as well as iron, the former giving a very clear metallic click on magnetisation.

I am much indebted to the kindness of Messrs. Johnson and Matthey for the bars of nickel and cobalt (9 inches long and 1 inch diameter) with which the experiments were conducted, and also to Mr. Gore, F.R.S., for the loan of a longer bar of nickel. Experiments are now in progress to determine the effect of temperatures and longitudinal tensions on the result.

Preliminary experiments show, that raising the temperature of the iron and cobalt bars some 50° C. makes a scarcely appreciable difference in the amount they elongate, whereas, when nickel is heated the same amount, its retraction on magnetisation is, as might be expected, considerably diminished, being about three-fourths of the amount occurring at the temperature of the air. Owing to the short length of the bars, the actual elongation measured was, in the case of the cobalt, only the 1-46,000th of an inch, but a difference of 100,000th of an inch could confidently be measured.

projected against them, and he went on to show that the higher above the sea-level the observer went, the darker the sky really is and the fainter the spectrum. In fact, the latter shows but little more than a band in the violet and ultraviolet at a height of 8500 feet, whilst at sea-level it shows nearly the whole photographic spectrum. The only reason of this must be particles of some reflecting matter from which sunlight is reflected. The author refers this to watery stuff of which nine-tenths is left behind at the altitude at which he worked. He then showed that the brightness of the ultra-violet of direct sunlight increased enormously the higher the observer went, but only to a certain point, for the spectrum suddenly terminated about 2940 wave-length. This abrupt absorption was due to extra atmospheric causes and perhaps to space. The increase in brightness of the ultra-violet was such that the usually invisible rays L, M, N could be distinctly seen showing that the visibility of these rays depended on the intensity of the radiation. The red and ultra-red part of the spectrum was also considere. He showed that the absorption lines were present in undiminished force and number at this high altitude, thus placing their origin to extra atmospheric causes. The absorption from atmospheric causes of radiant energy in these parts he showed was due to "water-stuff," which he hesitated to call aqueous vapour, since the banded spectrum of water was present, and not lines. The B and A line he also stated could not be claimed as telluric lines, much less as due to aqueous vapour, but must originate between the sun and our atmosphere. The author finally confirmed the presence of benzene and ethyl in the same region. He had found their presence indicate t in the spectrum at sea-level, and found their absorption lines with undiminished intensity at 8500 feet. Thus without much doubt hydrocarbons must exist between our atmosphere and the sun, and it may be in space.

PROF. LANGLEY, following Capt. Abney, observed: The very remarkable paper just read by Captain Abney has already brought information, upon some points which the one I am about, by the courtesy of the Association, to present, leaves in doubt. It will be understood then that the references here are to his published memoirs only, and not to what we have just heard.

The solar spectrum is so commonly supposed to have been mapped with completeness, that the statement that much more than one half its extent is not only unmapped but nearly unknown, may excite surprise. This statement is, however, I think, quite within the truth, as to that almost unexplored region discovered by the elder Herschel, which lying below the red and invisible to the eye, is so compressed by the prism, that though its aggregate heat effects have been studied through the thermopile, it is only by the recent researches of Capt. Abney that we have any certain knowledge of the lines of absorption there, even in part. Though the last named investigator has extended our knowledge of it to a point much beyond the lowest visible ray, there yet remains a still remoter region, more extensive than the whole visible spectrum, the study of which has been entered on at Alleghany, by means of the linear Bolometer. The whole spectrum, visible and invisible, is powerfully affected by the selective absorption of our atmosphere, and that of the sun; and we must first observe that could we get outside our earth's atmospheric shell, we should see a second and very different spectrum, and could we afterward remove the solar atmosphere also, we should have yet a third, different from either. The charts exhibited show:

Ist. The distribution of the solar energy as we receive it, at the earth's surface, throughout the entire invisible as well as visible portion, both on the prismatic and normal scales. This is what I have principally to speak of now, but this whole first research is but incidental to others upon the spectra before any absorption, which though incomplete, I wish to briefly allude to later. The other curves then indicate.

2nd. The distribution of energy before absorption by our own atmosphere.

3rd. This distribution at the photosophere of the sun. The extent of the field, newly studied, is shown by this draw

SUNLIGHT AND SKYLIGHT AT HIGH ALTI- ing (chart exhibited). Between H in the extreme violet, and A

TUDES

AT the Southampton meeting of the British Association, Captain Abney read a paper in which he called attention to the fact that photographs taken at high altitudes show skies that are nearly black by comparison with bright objects 'Phil. Mag., January, 1874.

in the furthest red, lies the visible spectrum, with which we are familiar, its length being about 4,000 of Ångstrom's units. If, then, 4,coo represent the length of the visible spectrum, the chart shows that the region below extends through 24,000 more, and so much of this as lies below wavelength, 12,000, I think, is now mapped for the first time.

We have to λ= 12,000, relatively complete photographs, pub

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