SECULAR CHANGES OF THE MAGNETIC ELEMENTS, OTTAWA, 1500–1930

1933 ◽  
Vol 9 (1) ◽  
pp. 94-96
Author(s):  
W. H. Herbert
Keyword(s):  
Magnetic Force ◽  
Secular Changes ◽  
Terrestrial Magnetism ◽  
Permanent Change ◽  
Magnetic Elements ◽  
Made In

In this paper is presented a table of the various elements of terrestrial magnetism at Ottawa from 1500 to 1930 and explains how the values were derived from old magnetic observations made in America, and not from theory. Among other points, it shows that though the total magnetic force has been declining at Ottawa for some time, yet the total magnetic force and the magnetic elements evidently go through cycles and none have apparently suffered permanent change during the time considered.

scholarly journals Contributions to terrestrial magnetism, No. 2

1843 ◽  
Vol 4 ◽  
pp. 287-289
Keyword(s):  
Magnetic Force ◽  
Volcanic Rocks ◽  
Mean Value ◽  
Full Detail ◽  
Terrestrial Magnetism ◽  
Independent Determination ◽  
Magnetic Elements ◽  
Future Improvement ◽  
Made In

This paper is the second of a series, in which the author purposes to communicate to the Royal Society the results of magnetic observations in different parts of the globe, having for their object to supply the requisite data for deducing the numerical elements corresponding to the present epoch of the general theory of terrestrial magnetism. It consists of two sections; the first comprises the observations of Captain Belcher, R. N., and the officers of H. M. S. Sulphur, at twenty-nine stations on the west coast of America, and the adjacent islands, between the latitudes of 60° 21' N. and 18° 05' S, The second contains a new determination, by the same officers, of the magnetic elements at Otaheite, made in consequence of the discrepancies in the results obtained by previous observers, and of a note in M. Gauss’s Allgemeine Theorie, in which Otaheite is spoken of as a highly important station for the future improvement of the calculations of the theory. Abstracts are given of the original observations which are deposited in the Hydrographic Office of the Admiralty, as well as a full detail of the processes of reduction by which their results have been computed. The values of the horizontal and total intensities are expressed in terms by which the results of observation are immediately comparable with the maps of MM. Gauss and Weber in the “Atlas des Erdmagnetismus.” By an investigation into the “probable error” of a single independent determination of the magnetic intensity with Hansteen’s apparatus, derived from the data furnished by Captain Belcher’s observations, the author shows the extreme improbability that the differences in the results obtained at Otaheite by Messrs. Erman, FitzRoy and Belcher, should be occasioned by instrumental or observational error. They are also far greater than can, with any degree of probability, be ascribed to periodical or accidental variations in the magnetic force from its mean value. The only known cause adequate to their explanation is what may with propriety be termed Station error ; that is, local disturbing influences, in an island composed chiefly of volcanic rocks, and where the spot of observation selected by the different observers may not have been precisely the same.

scholarly journals VI. Contributions to terrestrial magnetism.—No. XII. The magnetic survey of the British Islands, reduced to the epoch of 1842-5

1870 ◽  
Vol 18 (114-122) ◽  
pp. 532-532
Keyword(s):  
Magnetic Force ◽  
Secular Change ◽  
Magnetic Survey ◽  
Terrestrial Magnetism ◽  
Magnetic Elements

This paper contains a statement of the origin, progress, and completion of this survey. It is accompanied by maps of the declination, inclination, and magnetic force, which have been drawn at the Hydrographic Office of the Admiralty under the superintendence of Captain Frederick John Evans, R. N., F. R. S. The paper consists in great measure of Tables, giving the observation of each of the three magnetic elements, with reductions in every case for the secular change between the date of the observation and that of the epoch (1842-5) for which the maps are constructed.

scholarly journals XVI. Contributions to Terrestrial Magnetism, No. XI

1868 ◽  
Vol 16 ◽  
pp. 480-481
Keyword(s):  
Royal Society ◽  
Magnetic Force ◽  
British Association ◽  
Polar Regions ◽  
South Pole ◽  
The South ◽  
General Review ◽  
Terrestrial Magnetism ◽  
Magnetic Elements ◽  
South Polar

This number of the Contributions of Terrestrial Magnetism contains the completion of the Magnetical Survey of the South Polar Regions, undertaken by Her Majesty’s Government in 1840-1845 at the joint instance of the Royal Society and the British Association for the Advancement of Science. The observations themselves, and their provisional discussion, have already been given in the previous numbers, V., VI., VIII., and X. of the Contributions. The present number contains a general review of the whole survey, and is accompanied by three maps, which have been prepared, with the permission of the Hydrographer, Captain Richards, R. N., E. R. S., under the careful superintendence of the Assistant Hydrographer, Captain Frederick John Evans, R. N., F. R. S., one map being allotted to each of the three magnetic elements, viz. the Declination, Inclination, and Intensity of the Magnetic Force. In these maps the Isogonic, Isoclinal, and Isodynamic lines have been drawn, by the author of the paper, conformably with the observations around the circumference of the globe between the parallel of 30° S. and the South Pole. The paper also contains Tables, prepared with a view to the revision of the calculations of Gauss’s 'Allgemeine Theorie des Erdmagnetismus.’ They give the values of each of the three magnetic elements at the intersections of every fifth degree of latitude between 40° of south latitude and the South Pole, and every tenth degree of longitude between 0 and 360°.

scholarly journals On the means adopted in the British colonial magnetic observatories for determining the absolute values, secular change, and annual variation of the magnetic force

1851 ◽  
Vol 5 ◽  
pp. 942-944
Keyword(s):  
Magnetic Force ◽  
Mean Value ◽  
Probable Error ◽  
Secular Change ◽  
Equal Weight ◽  
Secular Changes ◽  
Terrestrial Magnetism ◽  
The Mean ◽  
The Absolute

The determination of the mean numerical values of the elements of terrestrial magnetism in direction and force at different points of the earth’s surface (the force being expressed in absolute measure, intelligible consequently to future generations, however distant, and conveying to them a knowledge of the present magnetic state of the globe), and the determination of the nature and amount of the secular changes which the elements are at present undergoing, are, as the author states, the first steps in that great inductive inquiry by which it may be hoped that the inhabitants of the globe may at some date, perhaps not very distant, obtain a complete knowledge of the laws of the phenomena of terrestrial magnetism, and possibly gain an insight into the physical causes of one of the most remarkable forces by which our planet is affected. After stating the inadequacy of the instruments originally proposed by the Royal Society, to the attainment of all the objects for which they had been designed, the author refers to the modifications which had been introduced, in the instruments and methods of observation for the determination of the absolute values, and the secular changes of the horizontal component of the magnetic force. He then gives the series of the results of the monthly observations at Toronto from January 1845 to April 1849 as relatively correct; and from this series, regarding each monthly determination as entitled to equal weight, and taking the arithmetical mean of all the values as the most probable mean value, obtains 3·53043 as the mean value of the horizontal force at Toronto, with a probable error of +·00055; and the probable error of +·0040 for each monthly determination.

scholarly journals I. Notices of some conclusions derived from the photographic records of the Kew declinometer, in the years 1858,1859, 1860, and 1861

1862 ◽  
Vol 11 ◽  
pp. 585-590
Keyword(s):  
Relative Frequency ◽  
Magnetic Force ◽  
Total Force ◽  
Magnetic Disturbances ◽  
Different Parts ◽  
Made In ◽  
Photographic Records

The discussion of the magnetic observations which have been made in different parts of the globe may now be considered to have established the three following important conclusions in regard to the magnetic disturbances: viz., 1. That these phenomena, whether of the declination, inclination, or total force, are subject in their mean effects to periodical laws, which determine their relative frequency and amount at different hours of the day and night. 2. That the disturbances which occasion westerly and those which occasion easterly deflections of the compass-needle, those which increase and those which decrease the inclination, and those which increase and those which decrease the magnetic force have all distinct and generally different periodical laws.

scholarly journals I. Note on an extension of the comparison of magnetic disturbances with magnetic effects inferred from observed terrestrial galvanic currents; and discussion of the magnetic effects inferred from galvanic currents on days of tranquil magnetism

1870 ◽  
Vol 18 (114-122) ◽  
pp. 183-185
Keyword(s):  
Magnetic Force ◽  
The Self ◽  
Instrumental Error ◽  
Magnetic Disturbance ◽  
Magnetic Effects ◽  
Royal Observatory ◽  
Moderate Disturbance ◽  
Magnetic Disturbances ◽  
Made In

The author, after referring to his paper in the Philosophical Transactions for 1868 on the comparison of Magnetic Disturbances inferred from Galvanic Currents recorded by the Self-registering Galvanometers of the Royal Observatory of Greenwich with the Magnetic Disturbances registered by the Magnetometers, on 17 days, states that he had now undertaken the examination of the whole of the Galvanic Currents recorded during the establishment of the Croydon and Dartford wires (from 1865 April 1 to 1867 October 24). The days of observation were divided into three groups,—No. I containing days of considerable magnetic disturbance, and therein including not only the 17 days above mentioned, but also 36 additional days, No. 2 containing days of moderate disturbance, of which no further use was made, and No. 3 containing the days of tranquil magnetism. The comparisons of the additional 36 disturbed days were made in the same manner as those of the preceding 17 days, and the inferences were the same. The results were shown in the same manner, by comparison of curves, which were exhibited to the Society. The points most worthy of notice are, that the general agreement of the strong irregularities, Galvanic and Magnetic, is very close, that the galvanic irregularities usually precede the magnetic, in time, and that the northerly magnetic force appears to be increased. The author remarks that no records appeared open to doubt as regards instrumental error, except those of western declination; and to remove this he had compared the Greenwich Curves with the Kew Curves, and had found them absolutely identical.

scholarly journals IX. On the magnetical results of the voyage of H. M. S. "Penguin," 1890-93

1896 ◽  
Vol 187 ◽  
pp. 345-381 ◽  
Keyword(s):  
Normal Values ◽  
Magnetic Survey ◽  
British Isles ◽  
Valuable Contribution ◽  
Terrestrial Magnetism ◽  
Magnetic Elements ◽  
Magnetic Disturbances

In the recent magnetic surveys conducted in different countries, the details of which have been published, one point stands out prominently from the rest, that the more minute the survey, the more surely do the observations show that the needle is subject to “local” and “regional” magnetic disturbances, varying in amount from the normal values of the magnetic elements, as deduced from extended observations made over the whole country. A reference alone to that recent and most valuable contribution to terrestrial magnetism, “A Magnetic Survey of the British Isles,” by Professors A. W. Rücker, F. R. S., and T. E. Thorpe, F. R. S., is quite sufficient to show the certainty of these disturbances.

scholarly journals XV. Results of magnetical observations made in Little Namaqualand during a part of the months of April and May, 1874

1875 ◽  
Vol 23 (156-163) ◽  
pp. 553-563
Keyword(s):  
The Sun ◽  
Magnetic Elements ◽  
Made In

An eclipse of the sun was to occur on April 16, 1874, which would be total throughout Little Namaqualand. I made arrangements for a visit to this country to observe the eclipse. The country is one rarely visited. I was not aware that any determinations of the magnetic elements had been made there, except a few of the variation by the Admiralty surveyors at one or two points along the coast. It appeared to me desirable that the opportunity afforded by my visit to observe the eclipse should not be lost of securing magnetical observations at several stations in Namaqualand.

scholarly journals XVII. Contributions to terrestrial magnetism. — No. VII

1846 ◽  
Vol 136 ◽  
pp. 237-336 ◽  
Keyword(s):  
New York ◽  
Magnetic Force ◽  
The Arctic ◽  
General View ◽  
Magnetic Survey ◽  
Terrestrial Magnetism ◽  
North American Continent ◽  
The North ◽  
Common Unit ◽  
The Moment

Containing a Magnetic Survey of a considerable portion of the North American Continent. From the moment that the fact was known, that the locality of the maximum of the magnetic Force in a hemisphere is not coincident, as was previously supposed, with the locality where the dip of the needle is 90°, researches in terrestrial magnetism assumed an interest and importance greatly exceeding that which they before pos­sessed; for it was obvious that the hypothesis which then generally prevailed regard­ing the distribution of the magnetic Force at the surface of the globe, and which had been based on a too-limited induction, was erroneous, and that even the broad out­ line of the general view of terrestrial magnetism had to be recast. The observations on which this discovery rested, (being those which I had had an opportunity of making in 1818, 1819 and 1820 within the Arctic Circle, and at New York in 1822,) were published in 1825*; they constituted, I may be permitted to say, an important feature in the views, which led the British Association in the year 1835 to request that a report should be prepared, in which the state of our knowledge in respect to the variations of the magnetic Force at different parts of the earth’s sur­face should be reviewed, and, as is customary in the reports presented to that very useful institution, that those measures should be pointed out which appeared most desirable for the advancement of this branch of science. In the maps attached to the report, the isodynamic lines on the surface of the globe were drawn simply in conformity with observations, and unmixed with hypothesis of any sort. The obser­vations collected for that purpose were not those of any particular individual or of any single nation, but embodied the results obtained by all persons who up to that period had taken part in such researches, subjected to such amount of discussion only as conveyed a knowledge of the modes of observation severally employed, and reduced the whole to a common unit.

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