Origin of the Chesil Bank

IN your report (vol. xi. p. 299) of the paper on this subject by Prof. Prestwich, read at the Institution of Civil Engineers, are these words:"The large dimensions of the bank he attributed to the great accumulative and small lateral action of the waves." Why, then, does not so general a cause form hundreds of such banks? Why is "the great accumulative action of the waves" confined solely to the Chesil Bank, and particularly to the Portland end of it? Because the travelling of the pebbles is towards Portland, which checks the travelling, and so allows of "

accu

mulation" exactly as a gro'n does. This is the simple "open sesame" of the secret; and if we could build groins as large as Portland, every one of them would "accumulate" a bank of precisely the same conditions as the Chesil Bank. If the pebbles travelled from Portland, as the professor thinks, that end of the bank should be the lowest; it would be perpetually robbed by the waves. But it is the highest-forty-three feet; and the Abbotsbury end, to which he supposes the pebbles to travel, should be the highest, but it is the lowest--scarcely more than half the height, twenty-three feet; while at Bridport there should be a still higher bank, for the professor makes the pebbles travel from east to west there and meet the pebbles which had "travelled from the opposite direction, viz., from west to east. But at Bridport there is not a single pebble, but only blown sand. That the largest pebbles accumulate at the leeward end of beaches is not a matter of opinion, but a matter of fact, and the fact may be seen at every groin in the world. So that the large pebbles at Portland, instead of testifying against the travelling from west to east, testify conclusively for it. If there is anyone who can suppose that the diminishing of the pebbles in size from Portland to Abbotsbury results from the wearing in travelling that distance, there can be no one who could give this cause for the same result between two groins. The cause which I have assigned (chapter on "Travelling of Sea Beaches," Rain and Rivers) for the lodgment of the largest pebbles at the Portland end, is that where motion is given to pebbles the largest will be on the outside; they are therefore most amenable to the upward and onward stroke of the wave, and they travel fastest and furthest down wind on these beaches.

With regard to the modern beaches being recompositions of ancient raised beaches, besides the travelling, their pebbles are perpetually pounded by the waves till they are ground into sand. The professor dates the Portland raised beach to the Glacial Period. We have ample time, then, for its pebbles to be ground into sand and replaced by new comers. And the new recruits

would not come, as the professor thinks, solely from "the cliffs," but chiefly from the mouths of the rivers which bring pebbles from all the various strata of the interior of the land without the aid of ice; for atmospheric disintegration and the erosion of rain denude the entire surface of the earth, and let down to the rivers not only soft soil but hard gravels and stones from every the most remote hill-top. But this huge traffic is brought to the rivers by rain. Rivers are simply the roads which it travels to the sea. What is held in suspension goes out to deep water, but the gravels, stones, and boulders are pounded and ground into the sands of the sea-shore. GEORGE GREENWOOD

Alresford, March 2.

Natural Phenomena in South America

It

IN Mr. J. Munro's very interesting notes made during a cablelaying expedition from Parà to Cayenne, which were published in NATURE, vol. xi. p. 329, the following passage occurs upon which comment may be useful. After describing a beautifully coloured Crustacean, and an animal which he speaks of as a crab or water-beetle, Mr. Munro goes on to say: "Another creature (Fig. 3) of quite a different description was also picked up. was more like a water-spider than anything else. Its transparent hair-like limbs were dappled with dull green, and it seemed a mere skeleton framework made to carry a small white sac containing entrails, which was slung underneath." From the figure it is tolerably evident that this creature is one of the Pycnogonidæ, whose place in a classification of the animal kingdom is scarcely yet definitely settled, but which are ranged by Prof. MilneEdwards among Crustaceans. It seems highly probable, then, that "the small white sac containing entrails" should rather have been described as a pair of very slender legs carrying egg. bags. This at least would be in accordance with what is known of other species of Pycnogons, none of which carry their entrails in sacs slung underneath.

Volcanic Action in the Sandwich Islands

IN your notice of my book, "The Hawaiian Archipelago," (vol. xi. p. 322), you allude to the statement that volcanic action on the Sandwich Islands "has died out from west to east." It has also died out in a southerly direction, through nearly four degrees of latitude. In the pit of Hale-mau-mau within the crater of Kilauea, on January 30, 1873, the violently agitated mass of lava continually took a southward direction, and broke in very elevated surges upon the cliffs on the south side of the lake. On June 4, 1873, when the aspect of the pit had undergone a sort of rotating whirlpool continually formed, invariably rotated very great change, there was a violent centripetal action, but the in a southerly direction. Some years ago, during a terrible erup. tion of Kilauea, when a river of lava from 200 to 800 feet wide, and an estimated depth of twenty feet, was running towards the sea with an estimated velocity of twenty-five miles an hour, four large "fire-fountains" boiled up when the stream issued from the earth. the lava was ejected with a rotary motion, and that both the lava An intelligent observer, Mr. Whitney, noticed that and stones thrown up rotated towards the south. I should be and if this apparently persistent southerly extinction and motion very glad to know any probable explanation of these phenomena, have any and what value as scientific facts?

Mr. Munro (vol. xi. p. 329) describes the locking together of trees of different species in the neighbourhood of Parà. The instances of this in the Hamakua forest on Hawaii are very numerous and striking. The Ohia (Metrosideros bolymorpha?) is seen in the closest conjunction with the large tree-fern of the district, with a universality which leads some people of more than average intelligence to assert dogmatically that the fern is the invariable parent of the Ohia! The junction is so intimate as to be apparent interpenetration. The greatest height of any tree-fern that I have measured is eighteen feet of caudex; but I have seen Ohias with an estimated height of eighty or ninety feet carry the tree-fern with them to a height of fully thirty feet, the fresh pea green fronds branching out from among the dark leaves and deep red blossoms of this very handsome evergreen. 6, Alva Street, Edinburgh, March 3 ISABELLA L. BIRD

The Height of Waves

THE height of waves has long been a vexed question amongst all classes of theoretical and practical observers. The late Admiral Fitzroy has left on record that on one occasion the measurement from crest to hollow was seventy feet. The figure seems high, but close and varied observations made during a storm on the passage from Liverpool to New York, in January, convinces me of the correctness of the Admiral's statement. In this storm, for the first time on record, large ocean steamers were rounded to with a fair wind, the universal opinion being that it was too dangerous to run with the sea far on the quarter. The captain of a German steamer, on arriving at New York, spoke in enthusiastic terms of the grand spectacle a White Star steamship presented as she "leaped from wave to wave like a gigantic fish," adding: "I am sure she must have hove to in the end."

This remarkable gale swept over a portion of the Atlantic which the French call "Le irou de diable," and it well merits the designation. Roughly, its focus may be considered to be in 45° N. and 40° W. When the wind sets in strongly from the north-west, the sea rises in an incredibly short space of time; and at the close of a long winter gale it is a grand sight to watch the great waves as they roll up astern at the rate of twenty-five miles per hour, sweep by the ship, and break far ahead. There is a feature in connection with the waves of the Atlantic which is worthy of notice, viz., with a south-west or southerly gale their height is insignificant. A practical proof of this is that large steamers run in the trough of the sea without inconvenience; but with less wind from the north-west they have occasionally to be kept off their course to avoid damage to boats. What occasions this remarkable phenomenon? It cannot be the "fetch," as seamen

term it, for in some positions the southerly is the longer. Neither can it arise from the lack of force on their part, for they often blow for days at a time, and the total number of foot pounds acting on any particular spot must be enormous. Again, a north-wester during winter or summer tears the surface of the water as if a harrow had passed over it, while the southerly gale leaves no trace behind, save the ordinary break of the crest. These are facts known to everyone who crosses the Atlantic, but no satisfactory explanation of their origin has yet been given. I give the data from which my observations were made, in order that anyone may draw his own conclusions. This ship is 450 feet long on the upper deck, and the fore yard is 62 feet above the level of the sea. From a position 239 feet abaft the foremast, where the height of the eye was 27 feet, the crests of the advancing waves at times appeared above the fore yard. Estimated distance between the crests of the waves, two-and-ahalf times the ship's length. WM. W. KIDDLE

Celtic, Feb. 13

"Linea "communicates the result of his examination of 2 747 on March 9; the magnitudes appeared to be 7 and 8, as in the last Greenwich Catalogue, the smaller star s.. If "Linea" refers to Astron. Nach. No. 2026, he will see from the position there given by Herr Falb for his new variable star, that there is no doubt of its identity with the preceding component of the above double star. It is also No. 10527 in the reduced catalogue of Lalande, and No. 274 in the volume of observations made at the Radcliffe Observatory, Oxford, in 1872, which has been circulated during the last week.

Mr. Birmingham, of Millbrook, Tuam, in Astron. Nach. No. 2028, draws attention to a star of 7th magnitude in Monoceros, which he appears to consider new. On Feb. 14, rough measures gave its position in R.A. 7h. 24m. 225., Decl. 10 4' S.; the colour was reddish-yellow. On looking to the sky, it is evident that the R.A. as printed is nearly one minute too great, and the star is identical with Lalande 14599, estimated 1797, Feb. 27, of the 6th magnitude. Lalande's place brought up to the beginning of the present year is R.A. 7h. 23m. 275*1.; N.P.D. 100° 4' 12". The star is entered 6 on Fellöcker's Berlin chart, but is not found in any recent catalogue. In all probability Mr. Birmingham has detected a new variable star. On March 14 it was very little below the 6th magnitude, and, in a hazy sky, had a deep yellow light.

MARS AND 3 SAGITTARII, 1875, JUNE 29.-A very close approach of this planet to the fifth magnitude star 3 Sagittarii will take place during the night of June 29;

indeed, with Leverrier's place and adopted diameter of the planet, the star would be occulted for a few minutes by the northern part of the disc, at the Observatories of Cordoba and Santiago de Chile. The phenomenon will not of the occultation of Aquarii on the 1st of October, be visible in this country. The much-desired observation 1672, during Richer's expedition to Cayenne, was lost, through a clouded sky, and from the same cause Rümker, at Paramatta, was prevented observing an occultation of 446 (Mayer) Leonis, on the 16th of February, 1822.

hemisphere with respect to the path of this comet after ENCKE'S COMET.—Inquiries arrive from the southern perihelion passage. The elements determined for the present year, after including the perturbations of Mercury, Venus, the Earth, Mars, Jupiter, and Saturn, are as follows according to Dr. von Asten :

Perihelion Passage 1875, April 13'06815 G. M. T.

THE TRANSIT OF VENUS

AS S we intimated last week, news has now been received more or less from all the Kerguelen parties. Details of the observations of these and other parties appeared in last Thursday's Times, and we shall here endeavour to present the principal astronomical results.

The weather on the island during the transport and after the landing of the various parties was horrible; the day before the Transit was one of the most trying kind, and at night the barometer was falling, and any observations on the morrow seemed hopeless. By a freak of the southern skies, however, on the morning of the 9th the sun rose without a cloud; but a bank began to form soon after sunrise. From the despatch of Capt. Fairfax, of the Volage, we learn that at the principal English station "the sky was cloudy and there was little wind. Venus was seen to break into the sun's disc, but before the internal contact a cloud had obscured the sun. Several observations and photographs of the sun were taken during the forenoon, and the internal and external contacts at egress were observed. At the other English stations and at the American stations the contact at ingress, but not at egress, was obtained. The Germans got both contacts at ingress and egress. The astronomers are pleased with their success." From an account of the observations made by the Americans, communicated by one of themselves to the Capetown Standard and Mail, and quoted by the Times, we learn that, all things considered, their success was great.

"The perfection of the calculations was surprisingly wonderful.

Not only was the angle of calculation drawn exactly, but the computed time was drawn to the nearest minute. After first contact, the measurement of cusps proceeded at intervals of five seconds. Near the moment of second contact, a cloud interposed, but it cleared away almost instantly, and enabled the astronomers to obtain the moment of second contact a little late, and to proceed with the measurement of distances of the limb of Venus from the sun's limb. This ended the part of the astronomical observers for the time being. Meanwhile the photographers were hard at work. During this time, half an hour, no fewer than forty-five photographs were taken of the sun, From this time until the Transit was over, photographs were taken whenever breaks in the mist gave the opportunity, the mist growing into clouds as the day wore on, gradually shutting out the sun from sight. In all, sixtyfive photographs were obtained, including several of the different stages of egress."

Our readers will no doubt remember what has been said about the high strategic value of Kerguelen. "For the Delislean method," to quote the article in the Times, "relied on by the English chiefly, it is the station at which (the Crozets being unoccupied) ingress was most retarded. Next in value to it from this point of view came St. Paul's Island (of which more presently), and then Bourbon, Mauritius, and Rodrigues.

Further, the entire Transit was visible from Kerguelen, therefore observations of duration could be made, and therefore it was a Halleyan station, and, let us add, the Southern Halleyan station of the very highest value. Thus, combining observations made at Nertchinsk and Kerguelen, we get a difference of duration of thirty-two minutes; the more easterly group of stations lying round New Zealand combined with Nertchinsk, only giving a difference of some twenty-eight minutes at the outside; and Mauritius, combined with the same place, only giving twenty-four minutes. For the photographic or direct method also it was of the highest importance, combining the photographs taken with those secured in Siberia and India. We are now, then, in a position to analyse the telegram: Observations of ingress retarded to combine with the observation of ingress accelerated, made at the Sandwich Islands, have been secured by three parties. We may say, then, that the Delislean observations have been successful. Unfortunately, we gather that the photographic record of the interior contact is wanting. This, however, is of less value, as the Sandwich Island party, with an ingenious confusion of the subjective and objective, have already informed us that 'Janssen failed.'

"As in no case did the same observer secure both ingress and egress, the value of the observations for the application of the Halleyan method is doubtful; but the last reference- Americans obtained some photographs '— may, when the work comes to be finally discussed, prove to be the most important of all, and astronomers all over the world will be very anxious to know the precise success attained, and it is very probable that it was great.

"Although we have thought well to wait for the news from Kerguelen before continuing our Notes, it must not be imagined that no intelligence of interest has been received since the last Notes appeared. On the contrary, the real interest is increasing as the details arrive; besides which, the French have received news from their parties at St. Paul's Island and Campbell Island, stations evidently outdoing even Kerguelen in the wretchedness entailed upon the observing parties, though that seems much to say after the report to the Admiralty which we published yesterday;" while details of the observations at New Caledonia were given in last week's NATURE by one who took part in them. "At St. Paul's Island the observations have been most satisfactory, as both internal contacts were observed and numerous photographs were obtained. This is good news for the partisans of all three methods, ingress being greatly retarded here, as before stated. Unfortunately, the still more heroic occupation of Campbell Island has been without result. Venus seen before ingress only; no contacts; all well,'

is the news telegraphed from San Francisco, which must have cost M. Bouquet de la Grye a heavy pang to send home.

"We next come to the more detailed accounts, and among these, that forwarded by M.Janssen to the Secretary of the French Academy of Sciences demands the first place. After describing all the care he took in the choice of his station, he goes on :

"Some days before the Transit, our fears were increased. Nevertheless, on the morning of the ninth the weather was pretty good, although the sky was a little overcast. The first contact was secured by M. Tisserand and myself. In the 8-inch equatorial, of which the object-glass is very good, the image of Venus appeared very round and well defined, and the relative motion of the disc of the planet with regard to the solar dise went on in a geometrical_manner, without any appearance of ligament or black drop. But rather a long time elapsed between the moment at which the disc of Venus was tangent to the sun's limb internally and that of the appearance of the fine line of light between them. This anomaly I ascribe to the atmosphere of the planet. I caused a photograph to be taken at the instant the contact appeared to be geometric, and on the plate the contact had not yet taken place. M. d'Almeida obtained a plate containing forty-seven photographs of the solar limb which leads to the same conclusions. I intend to discuss these observa. tions, which seem to me to lead to important consequences.

"After the first interior contact, M. Picard and M. Arens took as many photographs as possible, but the clouds greatly hindered us.

"Finally, near the second interior contact, the sun cleared as if providentially, and M. Tisserand was able to determine the time with precision. The sky was perfectly covered at the time of last exterior contact.

"During the Transit even we got news from Kobe that the first two contacts had been observed, and that fifteen photographs had been taken, and, finally, shortly after our own observations,

M. de la Croix announced that he had obtained the last two contacts, the last one only uncertain.

"He then concludes :

"I must not conclude without referring to an observation which relates to the corona and the coronal atmosphere of the sun. With glasses of a certain violet-blue colour, and very pure, I was enabled to see Venus before she had touched the sun's she commenced to bite into the sun's disc, this spot completed disc. She was visible as a small, very pale, round spot. When the black segment which was visible on the sun. It was a partial eclipse of the coronal atmosphere. . . . I saw Venus

two or three minutes of arc from the sun's limb.

greatest importance and interest. It seems not improbable "There are two points in Dr. Janssen's report of the that his observation of a geometric contact with the eye at the moment the contact was not complete to the photoobservation with the spectroscope, to which we have graphic plate may be connected with Prof. Tacchini's referred in previous Notes. If the observation may be depended upon-and Janssen, it is not too much to say, is one of the best astronomical observers living-it is clear that the sun built up by the blue rays was smaller than the sun built up by the particular rays which in the telescope employed produced white light.

This

"The second point is the observation of Venus on the coronal atmosphere by means of violet glass. attempt shows Janssen's genius in a remarkable manner. It is based upon the idea, derived from the eclipse work in 1871, that the coronal atmosphere is very rich in violet light, the idea in its turn being based upon the fact that the photographic corona is vastly different from the corona seen through a train of prisms. Of course, if this be so, the atmospheric light, which is not rich in violet rays, may be cut off by a glass of a dark-blue colour, which nevertheless will transmit the violet light coming from the corona, and so show Venus as a black spot.

"We condense the following details of the work done at the Australian stations from the Melbourne Argus — "At the Melbourne Observatory, presided over by Mr. R.L.J. Ellery, Government astronomer, the weather, by a happy chance,

cleared up in time for the observation of the important internal contact. The atmosphere was splendidly 'steady' in consequence of the previous fall of rain, and the effect of this was that the definition of the phenomenon was very distinct. There was no haziness or appearance of a black drop.' The contact was clear and tangential, and altogether free from the expected interferences with a good observation. During the contact and the following few moments, the photoheliograph was set to work, and numerous photographs of the ingress were obtained. They were taken rapidly at about two-second intervals, and about fifty were secured. The great telescope was used solely for photographing, in addition to the heliograph, but unfortunately it could not be brought into position quickly enough for photographs of the ingress to be taken by it, though it was used very effectively further on. The clouds then, as if they had just parted to allow of an observation at the critical moment, closed again over the sun, and its face remained obscured, with only occasional breaks, till between two and three o'clock. These breaks were availed of to obtain micrometric measures of the planet, which was now well on the sun's disc, and also to take photographs with the photoheliograph and the great telescope, which were very successfully obtained. Between two and three o'clock the weather began to clear up a little, and the observers were able to go more leisurely to work. The photographing went on well, though with several interruptions from passing clouds. The internal contact at egress, a very important point, was also observed very satisfactorily, although the atmosphere was a little more disturbed than during the internal contact at ingress, and there was observed a faint attempt at that appearance known as the 'black drop,' and a slight hazy ligament. For these reasons the internal contact at egress was not quite so satisfactorily observed as that at ingress, though a very good observation was made. During the egress a satisfactory series of micrometric measurements was made of the 'cusps,' and a rapid series of photographs was also obtained at two or three seconds' interval by means of the photoheliograph. The actual first internal contact was later than it was computed it would be by 3m. 13s. The first internal contact occurred at forty-five seconds after noon. The tabular time was 11h. 57m. 32s. The internal contact at egress occurred at 3h. 29m. 5s., or Im. 31s. after the computed time, which was set down in the tables at 3h. 30m. 36s.

"Two hundred Janssen photographs were taken, and on development they were found to be as satisfactory as could have been expected, considering the frequent interruptions from clouds, and they will probably furnish some very important data. Besides these, thirty-seven photographs were taken with the great telescope and forty-seven with the photoheliograph. These were only taken when the sun was unobscured.

"Mr. Russell, the Government astronomer at Sydney, reports as follows:-'Very fine at Sydney, also Woodford and Goulburn, and, I believe, Eden (Twofold Bay.) I obtained a good many photographs. No black drop. Contacts not obtainable to a fraction of a second.' Mr. Russell also states that a beautiful halo was visible around Venus (indicating the atmosphere), before the planet was wholly on the sun. The Government parties have a total of 1,300 photos.

"The German party at the Auckland Islands have been heard of; from ten minutes after ingress the weather was very fine, and 150 photographs were taken."

"Mr. Ellery, in a paper read before the Royal Society of Melbourne, has given some information of great importance from a physical point of view, consisting of a compilation of all the observations of this nature which have been forwarded to him :

"Mr. Anketell M. Henderson, observing with a Browning 81-inch Newtonian, writes :

It cleared about 11.40, and I got my first observation. Definition perfect; not the slightest tremor. At 11.53 or thereabout I was surprised by seeing the surface of Venus, outside the sun, distinctly visible on a faint phosphorescent-looking back. ground; it remained visible for about forty-five seconds, when clouds interfered.' Mr. C. Todd, of Adelaide, observing with an 8-inch refractor by Cooke and Son, remarked: For some time after internal contact at egress the portion of the planet which had moved off the sun was distinctly visible, appearing as though seen through a nebulous and luminous haze of a purplish hue, extending beyond and around the edge of the planet, and inclining to violet towards the sun.' He had received no other notes of the visibility of the disc of Venus outside the sun's disc

at egress, and he had been unable to get any trace of it himself, although the sky was clear and he looked for it. At Glenrowan the Transit was seen earlier than at Melbourne, and when the planet was about two-thirds on the sun Mr. Gilbert remarked, N.W. limb slightly luminous.' He then came to the appearance presented at internal contact, of which he noted as follows:'This phase was remarkably well seen, and was almost tangential and free from any haze, ligament, or other disturbance. The sky remained clear in the neighbourhood of the sun till after internal contact was well over. About half-past two, before contact, limb of sun appeared to bulge out so as to embrace Venus, the outwardly bent cusps continuing around Venus like a thread of silver. Occasionally a slight flicker between the limb of Venus and sun visible, then a hazy junction like thin smoke appeared, and finally a very faint smoky thread appeared to join the thin edges. This suddenly disappeared at oh. Im. 9'48, Melbourne time.' Mr. White's observations gave almost similar results. At Mornington the late Prof. Wilson noted a 'fluffy connection,' which is undoubtedly the same phase already noted, viz., 'smoky connection.' At the final junction the sun's edge was very tremulous, but the sky was quite clear. Prof. Wilson stated of this phase that the sun's edge was boiling. Venus did not look round, but as you might imagine a spherical balloon not quite blown up; the edge looked crumpled. A small dark object was seen flickering backwards and forwards between Venus and the edge of the sun. This increased, and there was no other phase to which I could attach a definite time.' At Sandhurst, Mr. Moerlin, observing with a 64-inch refractor, remarked: As the planet moved gradually near the sun's limb at exit, the sun's limb and planet appeared sharp and well defined, and the streak of light between the two was distinct and unmistakable. As it came nearer and nearer the same appear. ance was witnessed without any change whatever. The streak of light became smaller, and all at once a sort of triangularshaped connection between the two was observed, an appearance which I have seen with the artificial transit, but to a more limited extent, the base of the triangle on the sun's limb, the apex on the planet. The time when this phenomenon first appeared was 3h. 26m. 54 3s. The planet every once in a while jumped off the apex of the triangle, and the rim of the sun's disc could be distinctly seen between the two, the distance, however, between the triangle and the planet when jumping, growing less. The jumping or separating of the apex of the triangle and the planet ceased a few seconds before what I considered tangential contact.' Mr. Todd says, respecting this phase, that it was quite clear at egress, which was well observed; no black drop, but the continuity of the sun's disc was first broken by an exceedingly fine black line. The planet was seen to be slightly disturbed, the outline of the ball being apparently drawn out into a thin band.' With respect to an atmosphere surrounding Venus and the presence of a satellite, some of the observers had noticed towards the centre of Venus a light which condensed almost to a bright spot; and the Rev. Mr. Clarke, of Williamstown, observed a brownish orange halo surrounding Venus, and some others had observed a coloured light, though the difference of the tint was no doubt due to the eye-pieces used. He himself observed a blue light surrounding the planet, and made a careful scrutiny of it. He also called Mr. White and several others to observe, and they all saw it. He also noticed the granulatedor, as it was called, willow-leaved-appearance of the sun, which was very distinct, but approaching the planet presented a blurred appearance. With respect to the bright spot noticed in the centre of Venus, the same phenomenon was observed in the centre of Mercury during the transit of that planet.

"It has been suggested that all the observing parties at stations in or near Australia should meet about February in Melbourne, and compare their observations. Similar observations to those which have evidently attracted the attention of Mr. Ellery in a marked degree were perhaps made under the best possible conditions by Mr. Hennessey, at a height of between 7,000 and 8,000 feet in the Himalayas, and by other observers in India." His observations have been communicated to the Royal Society, and will be found in NATURE, vol. xi. p. 318.

"We must wait for some time for the final determination of the sun's distance as determined by the Transit observations, but no time need be lost in fully discussing the various physical questions raised, in order that we may be fully prepared for the Transit of 1882."

IN

THE PROGRESS OF THE TELEGRAPH

I.

N the present day scientific research makes such rapid progress, and produces such wonderful results, that the mind ceases to appreciate the advancement, which can only be realised by looking back, from time to time, to ascertain what was the condition of any special branch, any given number of years ago. It is only necessary to retrace time some twenty-five years, and in almost every department of practical science the step by step advancement may be traced, from sewing machines to steam hammers; from lucifer matches to lighthouses. But, perhaps, in no department of the applied sciences has scientific research been productive of more valuable and practical results than in the vast arena of electrical investigation; and great as has been the progress made in this department, still the knowledge obtained tends only to point out the vast field of research open to the student in discovering those fundamental laws and harmonies in nature's laboratory at present concealed from our view.

Sufficient, however, is already known in this special department of knowledge to inform us that electrical action and activity enters largely into the constitution of the solar system, regulating, in some degree at present not understood, the relation between the sun and our globe, as regards various terrestrial phenomena; as well as the disturbances upon the solar disc in relation to our earth's terrestrial and magnetic currents, as demonstrated in the daily deviations of the compass, and auroral displays in the regions adjacent to the polar latitudes of the earth Thus we see that whatever may be the vast field of research that remains to the student in this branch of scientific investigation, most important results have been developed. Time has been almost annihilated, and in the race between the earth's revolution on its axis, and electrical speech, man's inventive genius has been victorious-time and space being so far distanced that in electrical transmissions from one part of the globe's surface to another, time has no value as measured by the earth's rotation; messages sent from India and the East arriving hours before the time of their despatch. The introduction of the electric telegraph is quite within the memory of the present generation. Up to 1844 electrical knowledge was more or less confined to the lecturetable; crude experiments upon frictional electricity and the elements of magnetic and voltaic phenomena constituted the portfolio of knowledge as accepted by the public. The profound researches of Oersted in 1819 in relation to the influence of a current of electricity upon the magnetic needle is of great importance and may be summarised as follows:-A magnetic needle poised on a pivot so as to move freely in a horizontal plane adjusts itself in what is termed the magnetic meridian. If a metallic wire is placed parallel to the needle at a little distance above it, and a

FIG. 1Action of an electrical current on the magnetic needle.
(Oersted's experiment.)

current of electricity is passed through the wire, the magnetic needle will no longer remain parallel to the wire, but, leaving the magnetic meridian, will set itself across the current; and the same effect will be produced if the wire

is placed below the needle, and it will be found that if the direction of the current in passing through the wire is from S. to N., the north pole of the needle will be deflected in an opposite direction to where the current is passed from N. to S.; in other words, when the current nearest to the negative end of the battery always moves passes horizontally over the needle, that pole which is to the west, and when the current is passed under the needle the same pole will deviate to the east. Ampère in 1820, who employed the magnetic needle, the coil of wire, and the galvanic battery, to indicate signals, developed strated the fact that currents themselves exert an influence the principles of the discovery of Oersted, and demonon other currents. From the importance of Ampère's experiments in relation to all telegraph apparatus, a few words clearly illustrating the action of the current upon the magnetic needle are necessary.

FIG. 3.-Deviation to the left of the current. Lower current. needle, and the current from the positive pole of the battery to the negative pole is supposed to enter his feet and pass out at his head, the current will be found to develop a right and left influence on the magnetic needle, corresponding to the right and left of the person himself: so that when an electric current acts on a magnetic needle, the south pole of the needle-which is that which is directed towards the north-is deviated towards the left. Figs. 2 and 3 illustrate this: for when the parallel current is passed above the magnetic needle, the south pole a is deflected to A' to the left of the current, or towards the west; and on the current being passed below the needle, the same pole is deflected to A', being still to the left of the observer, but in this case the pole A has moved to the east. Ampère also demonstrated that when two metallic wires are traversed simultaneously by an electrical current, the wires are either attracted towards or repelled from each other according to the relative directions of the two currents. Thus, when they move in the same direction through the parallel wires, they attract each other, while they repel each other if they move in a contrary direction. Two non-parallel currents attract each other, if both are approaching or receding from the direction of the apex of the angle formed by the ends produced, while they will repel each other if one of the currents approach, and the other recedes from the apex of the angle. Fig. 4 illustrates the three cases of attrac tion and two cases of repulsion to which these laws of Ampère's refer. Ohm in 1827, who put forward his celebrated formulæ relating to the quantity of the galvanic