XXIV.—On the Lunar Diurnal Variation of Magnetic Declination at Trevandrum, near the Magnetic Equator, deduced from Observations made in the Observatory of His Highness the Maharajah of Travancore, G.C.S.I.

1872 ◽  
Vol 26 (4) ◽  
pp. 735-757
Author(s):  
J. A. Broun
Keyword(s):  
Diurnal Variation ◽  
Magnetic Force ◽  
Horizontal Component ◽  
Magnetic Equator ◽  
Horizontal Force ◽  
Magnetic Declination ◽  
Magnetic Needle ◽  
Made In

1. The lunar diurnal variation of magnetic declination as first discovered by Kreil, depended on too few observations to be free from the errors introduced by irregular disturbing causes. The independent discovery of the lunar action on the magnetic needle made afterwards by myself, was liable to the same criticism; but the agreement of the results obtained, both for the magnetic declination and the horizontal force, was sufficiently great to give a considerable value to the conclusion, that the magnetic needle obeys a diurnal law, depending on the moon's hour angle, both as to its direction and the force with which it is directed. This conclusion was farther confirmed in the discussion first made by myself, for the lunar diurnal variation of the vertical magnetic force, which gave, within an hour, the same epochs of maxima and minima as those obtained previously by me for the horizontal component.

XLV.—On the Diurnal Variation of the Magnetic Declination at Trevandrum, near the Magnetic Equator, and in both Hemispheres

1867 ◽  
Vol 24 (3) ◽  
pp. 669-690
Author(s):  
John Allan Broun
Keyword(s):  
Diurnal Variation ◽  
Magnetic Equator ◽  
Magnetic Declination ◽  
St Helena ◽  
Magnetic Needle ◽  
Made In

The first observations of the diurnal variation of magnetic declination, made near the equator, seem to have been those of Mr Macdonald, who observed in 1794–95 at Fort Marlborough, Sumatra, 3° 46′ S., and at St Helena. Two conclusions seem to have been deduced from these observations—1st, That near the equator the range of the diurnal variation was much smaller than in Europe; 2d, That the needle moved in opposite directions south of the equator and in Europe. This latter conclusion was made use of by M. Arago, in his report made in 1821, on the “Voyage de l'Uranie,” as the base of a hypothesis that there must be a line betwixt the two hemispheres on which the magnetic needle moves neither east nor west—that is, remains stationary. M. de Freycinet's observations showed that this line was not the terrestrial equator, and M. Arago supposed it must be the magnetic equator.

3. On the Lunar Diurnal Variation of Magnetic Declination at Trevandrum, near the Magnetic Equator

1872 ◽  
Vol 7 ◽  
pp. 756-758
Author(s):  
J. A. Broun
Keyword(s):  
Diurnal Variation ◽  
Diurnal Variations ◽  
Magnetic Equator ◽  
Magnetic Declination ◽  
The Law ◽  
The Times

The author gives the results derived from different discussions of nearly eighty thousand observations, made hourly during the eleven years 1854 to 1864. They are as follows:—1. That the lunar diurnal variation consists of a double maximum and minimum in each month of the year.2. That in December and January the maxima occur near the times of the moon's upper and lower passages of the meridian; while in June and July they occur six hours later, the minima then occurring near the times of the two passages.3. The change of the law for December and January to that for June and July does not happen, as in the case of the solar diurnal variations, by leaps in the course of a month (those of March and October), but more or less gradually for the different maxima and minima.

scholarly journals II. On the lunar diurnal variation of magnetic declination at the magnetic equator

1860 ◽  
Vol 10 ◽  
pp. 475-484
Keyword(s):  
Diurnal Variation ◽  
Careful Consideration ◽  
Magnetic Equator ◽  
Careful Examination ◽  
The Sun ◽  
The Moon ◽  
Magnetic Declination ◽  
The Law

This variation, first obtained by M. Kreil, next by myself, and afterwards by General Sabine, presents several anomalies which require careful consideration, and especially a careful examination of the methods employed to obtain the results. The law obtained seems to vary from place to place even in the same hemisphere and in the same latitude, and this to such an extent, that, for example, when the moon is on the inferior meridian at Toronto it produces a minimum of westerly declination; while for the moon on the inferior meridian of Prague and Makerstoun in Scotland it produces a maximum of westerly declination. No two places have as yet given exactly the same result; though the result for each place has been confirmed by the discussion of different periods. In order to obtain the lunar diurnal action, it has been usual to consider the magnetic declination at any time as depending on the sun’s and moon’s hour-angles and on irregular causes. Thus, if at conjunction, H 0 be the variation due to the sun on the meridian, and h 0 be that due to the moon on the meridian, H, the variation for the sun at 1 h , h 1 for the moon on the meridian of 1 h , and so on; it is supposed that we may represent the variations for a series of days by the following expressions, where the nearest values of h to the whole hour-angles are given:-

scholarly journals On the diurnal variation of the magnetic declination of St. Helena

1851 ◽  
Vol 5 ◽  
pp. 664-664
Keyword(s):  
Diurnal Variation ◽  
Northern Hemisphere ◽  
Opposite Direction ◽  
Diurnal Variations ◽  
The Sun ◽  
The Earth ◽  
Magnetic Declination ◽  
St Helena ◽  
Magnetic Needle

It has long been known that the diurnal variation of the magnetic needle is in an opposite direction in the southern, to what it is in the northern hemisphere; and it was therefore proposed as a pro­blem by Arago, Humboldt and others, to determine whether there exists any intermediate line of stations on the earth where those diurnal variations disappear. The results recorded in the present paper are founded on observations made at St. Helena during the five consecutive years, from 1841 to 1845 inclusive; and also on similar observations made at Singapore, in the years 1841 and 1842; and show that at these stations, which are intermediate between the northern and southern magnetic hemispheres, the diurnal variations still take place; but those peculiar to each hemisphere prevail at opposite seasons of the year, apparently in accordance with the position of the sun with relation to the earth’s equator.

scholarly journals II. On the law of disturbance and the range of the diurnal variation of magnetic declination near the magnetic equator, with reference to the moon’s hour-angle

1862 ◽  
Vol 11 ◽  
pp. 298-302
Keyword(s):  
Diurnal Variation ◽  
Magnetic Equator ◽  
Magnetic Declination ◽  
The Law

The discovery by Dr. Lamont of a "decennial” period in the range of the solar diurnal variation of magnetic declination, naturally leads to the question whether a similar law may not exist for the lunar diurnal variation; the question is also of importance in connexion with the theory of the cause of these variations.

XI. Results of the magnetic observations at the kew observatory. —No. III. Lunar diurnal variation of the three magnetic elements

1867 ◽  
Vol 15 ◽  
pp. 249-250
Keyword(s):  
Diurnal Variation ◽  
Magnetic Force ◽  
Magnetic Declination ◽  
Magnetic Elements ◽  
The Subject ◽  
Photographic Records

The subject of this paper is the lunar-diurnal variation of the magnetic declination and of the horizontal and vertical components of the magnetic force, derived from a seven years’ series of photographic records obtained at the Kew Observatory between January 1, 1858 and December 31, 1864.

scholarly journals III. On the annual variation of the magnetic declination

1874 ◽  
Vol 22 (148-155) ◽  
pp. 254-258
Keyword(s):  
Annual Variation ◽  
Modern Times ◽  
Magnetic Declination ◽  
The World ◽  
The Mean ◽  
Magnetic Needle ◽  
Different Parts ◽  
Made In

The first observations which seemed to show that the mean position of the declination-needle followed an annual law were those of Cassini, made, more than eighty years ago, in the hall of the Paris Observatory and in the caves below it (90 feet under ground). It cannot be said, however, that Cassini’s result has been confirmed by subsequent observations, either as regards the direction or amounts of movement from month to month. The extensive series of observations made in different parts of the world in modern times have given results so different that we must conclude either that the magnetic needle obeys different annual laws at each place, or that the differences are due to instrumental errors. The consequence has been that, after long, laborious, and expensive researches, it is still a question whether the magnetic needle obeys an annual law or not.

scholarly journals II. On the solar and lunar variations of magnetic declination at Bombay.”—Part I

1869 ◽  
Vol 17 ◽  
pp. 161-163
Keyword(s):  
Diurnal Variation ◽  
Present Discussion ◽  
Magnetic Declination ◽  
The Government ◽  
Made In

The hourly observations of magnetic declination at the Government Observatory, Bombay, have extended over a period of nearly a quarter of a century, but the present discussion is confined to the observations made in the seven years 1859 to 1865. After describing the instrument with which the observations were made and the method of reducing them, the writer exhibits, by means of Tables and curves, the following results:— 1st. The agreement of the diurnal variation of the aggregate of easterly disturbances when different separating values are adopted. 2nd. The same for the aggregate of westerly disturbances. 3rd. The diurnal variation of the aggregate of easterly disturbances, exceeding l'.4 in amount, in the period of seven years.

scholarly journals II. On the evidence of the existence of the decennial inequality in the solar-diurnal variations, and its non-existence in the lunar-diurnal variation of the magnetic declination at Hobarton

1857 ◽  
Vol 8 ◽  
pp. 314-315
Keyword(s):  
Diurnal Variation ◽  
Royal Society ◽  
Diurnal Variations ◽  
Horizontal Component ◽  
The Moon ◽  
Magnetic Declination ◽  
Magnetic Variation ◽  
Imperial Academy ◽  
Academy Of Sciences

In a communication made to the Royal Society in the last Session, “On the Lunar-diurnal Magnetic Variation at Toronto,” the author had stated that he could discover no trace of the lunar influence of the decennial inequality which constitutes so marked a feature in the solar magnetic variations. He has since read, in a memoir communicated to the Imperial Academy of Sciences at Vienna, entitled “On the Influence of the Moon on the horizontal component of the Mag­netic Force,” that M. Kreil is of opinion that the observations of different years at Milan and Prague, when combined, would rather favour the contrary inference, viz. that the decennial inequality exists in the lunar as well as in the solar variations.

V. On the influence of height in the atmosphere on the diurnal variation of the earth’s magnetic force

1877 ◽  
Vol 25 (171-178) ◽  
pp. 566-569
Keyword(s):  
Diurnal Variation ◽  
Magnetic Force ◽  
Absolute Intensity ◽  
The State ◽  
The Other ◽  
Horizontal Force ◽  
Magnetic Intensity ◽  
Diurnal Range ◽  
The Mean ◽  
The Absolute

In a paper in the Society’s Transactions on the earth’s magnetic intensity at Bombay, Mr. C. Chambers has examined the question of the influence of height on the diurnal inequality of the horizontal force. Two instruments were observed simultaneously at 0 h 22 m and 2 h 29 m p. m.: one, a bifilar magnetometer, was 6 feet above the ground; the other, a unifilar absolute-intensity instrument, was 38 feet above the ground. Mr. Chambers has found that, in the interval between the two times specified, the change of horizontal force given by the bifilar magnetometer was rather more than one third (0*37) of the mean diurnal range, and that the absolute- intensity instrument showed a change about one fifth less than the bifilar. This difference he does not think instrumental; and he considers that, if true, “ it suggests the attribution of a very con­siderable magnetic influence to the state of the medium intervening between the upper and lower places of observation,” &c.

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