scholarly journals I. Magnetic observations taken during the transit of venus expedition to and from Kerguelen Island

1878 ◽  
Vol 27 (185-189) ◽  
pp. 1-11 ◽  
Keyword(s):  
Magnetic Force ◽  
Cape Town ◽  
Mean Values ◽  
Terrestrial Magnetism ◽  
Kerguelen Island ◽  
Cape Of Good Hope ◽  
Complete Survey ◽  
Port Said

In a previous paper, on the elements of terrestrial magnetism observed at Kerguelen, the reason is mentioned why it was not deemed advisable to take magnetic observations at sea during the voyage; the results, therefore, in this paper are entirely confined to the determina­tions of the Dip, Intensity, and Declination of the earth’s magnetic force at the several places at which we landed. On our outward journey we had no opportunity of using our instruments, except at the Cape of Good Hope, but on our return we were much more fortunate, as H.M.S. “Volage” made a stay of at least two days at Point de Galle, at Bombay, Aden, Port Said, and Malta, and we utilised all these opportunities except the first. From Malta, the Rev. W. Sidgreaves and myself returned to England by Sicily, Italy, and France, and, taking our magnetic instruments with us, we were able to observe at Palermo, Naples, Rome, Florence, and Moncalieri. As we had previously made a complete survey of France in 1868 and 1869, we thought it too early to repeat the observations. The instrumental corrections and constants have already been given in the former paper on Kerguelen, it will, therefore, suffice to refer to that communication for any necessary details. The long sea voyage, with its great variation ,of temperature, was very trying for the delicate portions of the instruments, and as we found that No. 1 Needle had been slightly injured by rust, it was never used during our home journey. In the last column of Table II the daily mean values of the dip are entered, but it was only at Cape Town and at Bombay that observations could be taken on more than a single day. Needle No. 2 seems to read about 30” higher than No. 3, but no correction has been applied to either, as the amount is considerably less than the usual errors of observations.

II. Contributions to terrestrial magnetism. — No. III

1842 ◽  
Vol 132 ◽  
pp. 9-41 ◽  
Keyword(s):  
Base Station ◽  
Magnetic Intensity ◽  
Equivalent Weight ◽  
Constant Weight ◽  
Terrestrial Magnetism ◽  
Kerguelen Island ◽  
Cape Of Good Hope ◽  
Bad Weather ◽  
St Helena ◽  
Grooved Wheel

In the present number of these Contributions, I propose to give an account of the observations on the magnetic intensity made at sea by the officers of Her Majesty’s ships Erebus and Terror, on their passage from England to Kerguelen Island, the unreduced observations, transmitted to the Admiralty by the Commanders, Captains Ross and Crozier, having been placed in my hands for that purpose. They will be divided for convenience into two sections, viz. 5. Observations between England and the Cape of Good Hope . 6. Observations between the Cape of Good Hope and Kerguelen Island . 5. Observations between England and the Cape of Good Hope . The observations in the Erebus were made by the statical method devised by Mr. Fox, with one of his instruments of 7½ inches diameter. The intensities were measured by the angles of deflection produced, in different localities, by a constant weight applied to a grooved wheel on the axle of the needle; and the ratio of the intensities is inversely as the sines of the angles of deflection, subject to a correction for differences of temperature of the needle, computed by the formula ⋅00016 I' ( t ' — t ), in which t is the standard and t ' the observed temperature in degrees of Fahrenheit, ⋅00016 a coefficient determined experimentally by Mr. Fox, and I' the observed intensity. At sea, where the manipulation of the weights causes an exposure of the needle, which, in bad weather particularly, is liable to occasion injury, the plan recommended by Mr. Fox, of using deflecting magnets instead of weights, was frequently resorted to. In this case the ratio of the intensity in different localities is inversely as the sines of the angles of deflection, and directly as the weights equivalent to the deflecting force of the deflector on the needle at the respective angles; or I' = I. w' / w ⋅ sin v /sin v' where I, v , and w are the intensity, angle of deflection, and equivalent weight at a base station; and I', v' and w' corresponding values at another station. A table is usually formed for each instrument experimentally, under Mr. Fox’s own direction, of the equivalent, or as they are termed by him, the coercing weights, for each deflector on each of the needles at the different angles which are likely to occur in the course of the observations. This is done by placing the deflector successively at angles from the dip, each differing one degree from the preceding; the needle is thereby deflected to a smaller angle on the side of the dip opposite to the deflector, and is brought back to the dip by a weight applied to the grooved wheel on the axle; this weight is called the coercing weight corresponding to the angle from the dip at which the deflector was placed. For greater accuracy, the table is formed from results obtained by placing the deflector successively on either side of the needle. Owing to accidental circumstances, no table of this description was prepared for this instrument before the Expedition sailed; the pressure of other duties prevented its being done at St. Helena, the Cape of Good Hope, or at Kerguelen Island; and at Van Diemen Island the end of the axle of the needle being accidentally broken, the needle was returned to England to be repaired, and was thus separated from the instrument and from the deflectors. Under these circumstances we have no other resource for reducing the observations made with the deflectors, than to form a table from the observations of the weights and deflectors (when both methods have been employed at the same station), which shall answer the same purpose as a table of coercing weights. Fortunately the number of such stations is considerable.

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.

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.

Culture and Society at the Cape of Good Hope, 1652–1795

2020 ◽  
Author(s):  
Gerald Groenewald
Keyword(s):  
18Th Century ◽  
Cape Town ◽  
Natural Increase ◽  
East India Company ◽  
Dutch East India Company ◽  
Male Population ◽  
East Indies ◽  
Cape Of Good Hope ◽  
Entrepreneurial Activities ◽  
Settler Population

In 1652 the Dutch East India Company founded a “refreshment station” in Table Bay on the southwestern coast of Africa for its fleets to and from the East Indies. Within a few years, this outpost developed into a fully-fledged settler colony with a “free-burgher” population who made an existence as grain, wine, and livestock farmers in the interior, or engaged in entrepreneurial activities in Cape Town, the largest settlement in the colony. The corollary of this development was the subjugation of the indigenous Khoikhoi and San inhabitants of the region, and the importation and use of a relatively large slave labor force in the agrarian and urban economies. The colony continued to expand throughout the 18th century due to continued immigration from Europe and the rapid growth of the settler population through natural increase. During that century, about one-third of the colony’s population lived in Cape Town, a cosmopolitan harbor city with a large transient, and overwhelmingly male, population which remained connected with both the Atlantic and Indian Ocean worlds. The unique society and culture that developed at the Cape was influenced by both these worlds. Although in many ways, the managerial superstructure of the Cape was similar to that of a Dutch city, the cosmopolitan and diverse nature of its population meant that a variety of identities and cultures co-existed alongside each other and found expression in a variety of public forms.

scholarly journals Polyzoa

1879 ◽  
Vol 168 ◽  
pp. 193-199 ◽  
Keyword(s):  
New Zealand ◽  
The Arctic ◽  
Kerguelen Island ◽  
Cape Of Good Hope ◽  
Whole Number ◽  
Westerly Direction ◽  
Southern Extremity

Owing to the absence of any published accounts of the Polyzoa collected at Kerguelen Island by the Challenger, the American Transit of Venus, and the German Surveying and Transit of Venus Expeditions in 1874-75, the subjoined list treats exclusively of Mr. Eaton’s collection. The 26 or 27 species comprised in it are all of them inhabitants of the littoral or Laminarian zone, and were obtained with the grapple in Swain’s Bay and Observatory Bay. Of the whole number 17 or 18 belong to the suborder Cheilostomata , 9 to the Cyclostomata . No representative of the Ctenostomata was collected. The collection affords nine or ten forms previously undescribed; the remainder belong to a fauna which ranges from the southern extremity of S. America (which may be regarded as its “centre”) to New Zealand in a westerly direction, one or two species extending even farther, to Australia and the Cape of Good Hope. It is observable that no Arctic form has been brought from Kerguelen Island, although some have been met with further south, two instances of the occurrence of the Arctic Horneva lichenoides obtained during the voyage of H. M. SS. “Erebus” and “Terror” having been communicated to me by Sir J. Hooker. Mr. Eaton suspects their absence may be attributed to the shallowness of the areas searched by him, the greatest depth being not more than 10 fathoms.

scholarly journals XX. Contributions to terrestrial magnetism.-no. x

1866 ◽  
Vol 156 ◽  
pp. 453-543
Keyword(s):  
Southern Ocean ◽  
Falkland Islands ◽  
Magnetic Survey ◽  
Present Communication ◽  
Terrestrial Magnetism ◽  
Cape Of Good Hope ◽  
General Plan ◽  
Detailed Exposition ◽  
Magnetic Elements ◽  
The Antarctic

Resume in this Number of the Contributions the discussion and coordination of the observations of the Antarctic Magnetic Survey executed by Her Majesty’s Ships ‘Erebus’ and ‘Terror,’ under the direction of Sir James Clark Ross, R. N., aided by Captain Francis Rawdon Crozier, R. N., between the years 1839 and 1843. I purpose in the present communication to complete the detailed exposition of the Survey by the reduction of the observations of the three magnetic elements in its con­cluding year, on the same general plan on which similar accounts were given of those of the preceding years in earlier communications, viz., between the Cape of Good Hope and Hobarton in 1840, and between the departure from Hobarton in November 1840, and the return to the same station in April 1841, in No. V. (Philosophical Transactions, 1843, Art. X ) ; and between Hobarton in July 1841 and the Falkland Islands in April 1842 in No. VI. (Philosophical Transactions, 1844, Art. VII.). The observations discussed in the present memoir are those made from the departure from the Falkland Islands in September 1842 to the second arrival at the Cape of Good Hope in April 1843. In a subsequent and concluding memoir, which I hope to present to the Society early in the ensuing session, it will be my endeavour to connect and thoroughly coordinate the several portions of the Survey, comprising in its three portions the circumnavigation of the Southern Ocean from the departure from the Cape of Good Hope in March 1840, to the return of the ships to the same station in April 1843.

scholarly journals II. On the automatic registration of magnetometers, and meteorological instruments, by photography. —No. IV

1852 ◽  
Vol 142 ◽  
pp. 19-24 ◽  
Keyword(s):  
Royal Society ◽  
Temperature Compensation ◽  
Magnetic Force ◽  
Automatic Correction ◽  
Automatic Registration ◽  
Automatic Temperature ◽  
Mean Values ◽  
The Government ◽  
Meteorological Instruments

On the Automatic Temperature Compensation of the Force Magnetometers . A portion of the funds liberally contributed by the Government for the advancement of science, and placed at the disposal of the President and Council of the Royal Society, having been entrusted to the author for the accomplishment of the above object on a plan which was submitted to the Astronomer Royal and Colonel Sabine in the spring of last year, and by them considered feasible, he considers that he cannot better fulfil the obligation of reporting progress at the present period, than by laying before the Royal Society a description of the instruments now constructed. So long as the results of the variations of magnetic force were deduced from eyeobservation only, at the periods of which the temperature as well as the position of the magnets was recorded, a correction for the influence of change of temperature on the instruments themselves could be readily estimated and applied; but in deducing mean values from the photographic registers, especially those for intervals involving considerable changes of temperature, it is manifest that the greatest degree of accuracy cannot be attained, unless either the apparent values were individually corrected by means of a separate register of the thermometer enclosed in the box with the magnet, or the instrument possessed within itself an approximate automatic correction for the effects of change of temperature.

Observations made at the Cape of Good Hope, in the year 1838, with Bradley's zenith sector, for the verification of the amplitude of the Abbé de la Caille’s arc of the meridian; by order of the lords commissioners of the admiralty

1843 ◽  
Vol 4 ◽  
pp. 192-193
Keyword(s):  
Cape Town ◽  
Plumb Line ◽  
Great Credit ◽  
Cape Of Good Hope ◽  
Table Mountain ◽  
Royal Observatory ◽  
Different Parts

The author gives an account of the precautions taken in putting together the different parts of the zenith sector, which he received on the 9th of December, 1837, in erecting it in the central room of the Royal Observatory at the Cape of Good Hope, and in afterwards transferring it to the southern station of La Caille, in Cape Town. He then proceeds to describe La Caille’s observatory, and the particular circumstances of its locality, with relation to the object in view namely to determine the influence of Table Mountain on the direction of the plumb-line. He next relates his progress to Klyp Fonteyn, where he arrived on the 24th of March, 1838, and describes the operations resorted to for erecting the sector at that place. He then enters into the details of observations made at different stations, and especially with comparative observations at the summit and foot of the mountain of Pequet Berg. The instrument was lastly conveyed back to Cape Town, and again examined, and the observations made with it repeated. The reduction of the observations occupies the remainder of the paper; and in conclusion, the author remarks, that although these labours have not altogether cleared up the anomaly of La Caille’s arc, yet they show that great credit is due to that distinguished astronomer, who with imperfect means, and at the period in which he lived, arrived at a result, derived from sixteen stars, almost identical with that from 1139 observations on forty stars, made with a celebrated and powerful instrument.

scholarly journals IV. Contributions to terrestrial magnetism.—No. X

1867 ◽  
Vol 15 ◽  
pp. 209-209
Keyword(s):  
Original Work ◽  
Numerical Data ◽  
Full Detail ◽  
Magnetic Survey ◽  
Terrestrial Magnetism ◽  
The Third ◽  
Cape Of Good Hope ◽  
Magnetic Elements ◽  
Considerable Length ◽  
Equidistant Points

In this number of the Contributions to Terrestrial Magnetism the author resumes the discussion of the results obtained in the Magnetic Survey of the Southern Ocean by the Expedition under Sir James Clark Ross, R. N., and Captain Francis Rawdon Crozier, R. N., between the years 1839 and 1843. The proceedings during the two first years of this Survey have been the subjects of two preceding numbers of the Contributions, viz. of Nos. V. and VI., in the Philosophical Transactions for 1843 and 1844. The present number contains a similarly detailed exposition of the operations of the third year of the Survey, comprehending the Southern Atlantic between Cape Horn and the Cape of Good Hope, and completing the circumnavigation of the southern hemisphere, from the departure of the expedition from the Cape of Good Hope in March 1840, to the return to the same station in April 1843. In a subsequent memoir, which will be presented to the Royal Society early in the ensuing Session, the author proposes to connect and thoroughly coordinate the three portions of the Survey, and to supply from them the numerical data at equidistant points on each of the three parallels of 50°, 60°, and 70° of south latitude, of the three magnetic elements, which will be required for a revision of the 'Allgemeine Theorie des Erdmagnetismus’ of M. Gauss—the 40th parallel having been the most southern available at the epoch of the publication of the original work. The instruments employed in this Survey, as well as the methods of employing them, and of eliminating the disturbing influence of the iron in the equipment of the vessels, having been in a great measure of a novel character, a discussion of considerable length bearing on all such points is prefixed to a full detail of the observations themselves, arranged in Tables, showing in every instance both the immediate results of the observations, and the corrections which have been applied in conformity with the principles contained in the preliminary discussion. Tabular abstracts are also furnished, exhibiting the results of the determinations of each day, with the appropriate geographical positions.

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