Report of a Joint Committee of Physics and Meteorology referred to, by the Council of the Royal Society, for an opinion on the propriety of recommending to Her Majesty’s Government, the establishment of fixed magnetic observatories, and the equipment of a naval expedition for magnetic observations in the Antarctic Seas, and to report generally on the subject: together with the resolutions adopted on that Report, by the Council of of the Royal Society.

The subject of terrestrial magnetism has recently received some very important accessions which have materially affected not only the point of view in which henceforward it will be theoretically contemplated, but also the modes of observation which will require to be adopted for completing our knowledge of the actual state of the magnetic phenomena, and furnishing accurate data for the construction and verification of theoretical systems. It was for a long time supposed that the changes in the position assumed by the needle at any particular point on the earth’s surface might be conceived as resulting from regular laws of periodicity, having for their arguments, first, great magnetic cycle of several centuries, depending on unknown, and perhaps internal movements or relations; and secondly, on the periodic alternations of heat and cold, depending on the annual and diurnal movements of the sun. The discovery of the affection of the needle by the aurora borealis, and of the existence of minute and irregular movements, which might be referred either to unperceived auroras or to other local and temporary causes, sufficed to show that the laws of terrestrial magnetism are not so simple as to admit of this summary form of expression; and the important discovery, first announced, we believe, by Baron Von Humboldt, that those temporary changes take place simultaneously at great distances in point of locality, a discovery which has since been remarkably confirmed and extended to very great intervals of distance, so as to include the whole extent of the European continent, by Gauss and Weber, and their coadjutors of the German Magnetic  Association, has sufficed to show that the gist of inquiry lies deeper, and depends upon relations far more complex, while at the same time the dominion of what might previously have been regarded as local agency, would require, in the new views consequent on the establishment of these facts, to be extended far beyond what ordinary usage would authorize as a just application of that epithet.

For a long time in the history of terrestrial magnetism the variation alone was attended to. The consideration of the dip was then superadded; but the observation of this element being more difficult and delicate, our knowledge of the actual and past state of the dip over the earth’s surface is lamentably deficient. It has lately appeared, however, that this element can be observed with considerable approximation, though not with nicety, at sea, so that no reason subsists why materials for a chart of the dip analogous to that of variation should not be systematically collected. Lastly, the intensity has come to be added to the list of observanda; and from the great facility and exactness with which it can be determined, this branch of magnetic knowledge has in fact made most rapid progress.

These three elements, the horizontal direction, the dip, and the intensity, require to be precisely ascertained before the magnetic state of any given station on the globe can be said to be fully determined. Nor can either of them, theoretically speaking, be said to be more important than the others, though the direction, on account of its immediate use to navigators, has hitherto had the greatest stress laid upon it, and been reduced into elaborate charts. A chart of the lines of total intensity has been recently constructed by major Sabine.

All these elements are, at each point, now ascertained to be in a constant state of fluctuation, and affected by those transient and irregular changes which are above alluded to; and the investigation of the laws, extent, and mutual relations of these changes is now become essential to the successful prosecution of magnetic discovery, for the following reasons:—

First. That the progressive and periodical being mixed up with the transitory changes, it is impossible to separate them, so as to obtain a correct knowledge and analysis of the former, without taking express account of and eliminating the latter, any more than it would be practicable to obtain measures of the sea-level available for an inquiry into the tides, without destroying the irregular fluctuation produced by waves.

Secondly. That the secular magnetic changes cannot be concluded from comparatively short series of observations without giving to those observations extreme nicety, so as to determine with perfect precision the mean state of the elements at the two extremes of the period embraced, which, as already observed, presupposes a knowledge of the casual deviation.

Thirdly. It seems very probable that discordances found to exist between results obtained by different observers, or by the same at different times, may be, in fact, not owing to error of observation, but may be due to the influence of these transitory fluctuations in the elements themselves.

Fourthly and lastly. Because the theory of these transitory changes is in itself, one of the most interesting and important points to which the attention of magnetic enquirers can be turned, as they are no doubt intimately connected with the general causes of terrestrial magnetism, and will probably lead us to a much more perfect knowledge of those causes than we now possess.

Actuated by these impressions, on the occasion of a letter addressed by Baron Von Humboldt to His Royal Highness the Duke of Sussex, P.R.S., the Council of this Society, on April 13th, 1837, resolved to apply to Government for aid in prosecuting, in conjunction with the German Magnetic Association, a series of simultaneous observation; and in consequence of an application founded on such their resolution, a grant of money was obtained for the purchase of instruments for that purpose. By reason, however, of the details and manipulations of the methods then recently introduced into magnetic observations by Gauss being at that time neither completely perfected, nor their superiority over the old methods fully established by general practice, the precise apparatus to be employed in these operations was not at the time agreed upon, and was still under discussion, subject to the report of the Astronomer-Royal on the performance of an instrument on Gauss’s principle established at Greenwich, at the time when the subject in its present more extended form was referred by the Council to this Joint Committee, so that the grant in question has not in point of fact, been employed or called for. The Committee consider this as in some respect fortunate, as in consequence of the delay, time has been given for a much maturer consideration of the whole subject; and should it now be taken up as a matter of public concern, they consider that it will be necessary to provide for a more continuous and systematic series of observations, by observers regularly appointed for the purpose, and provided with instruments and means considerably more costly than those contemplated on the occasion in question.

On the general advisableness of calling for public assistance in the prosecution of the extensive subject of terrestrial magnetism, in both the modes referred to them for their consideration, (viz. by magnetic observatories established at several stations properly selected on land, and by a naval expedition expressly directed to such observations in the Antarctic Seas,) your committee are fully agreed. They consider the subject to have now attained a degree of theoretical as well as of practical importance, and to afford a scope for the application of exact inquiry which it has never before enjoyed, and which are such as fully to justify its recommendation by the Royal Society to a revival of that national support to which we are indebted for the first chart of variations constructed by our illustrious countryman Halley, in A.D. 1701, on the basis of observations collected on a voyage of discovery expressly equipped for that purpose by the British Government.

As regards the first branch of the question referred to their consideration, they are of opinion that the stations which have been suggested to them, viz. Canada, St. Helena, the Cape, Van Diemen’s Land, and Ceylon (or Madras), are well selected, and perhaps as numerous as they could venture to recommend, considering the expense which would require to be incurred at each, and that in each of these stations it would be desirable, first;—that the regular hourly observations should be made (at least during the day-time) of the fluctuations of the three elements of variation, the dip, and intensity, or their equivalents, with magnetometers on the more improved construction, during a period of three years from their commencement.

Secondly. That on days, and on a plan appointed, agreed on in concert with another, and with European observatories, the fluctuations of the same elements should be observed during twenty-four successive hours, strictly simultaneous with one another, and at intervals of not more than five minutes.

Thirdly. That the absolute values of the same elements shall be determined at each station, in reference to the fluctuating values above mentioned, with all possible care and precision, at several epochs comprehended within the period allowed.

Fourthly. That in the event of a naval expedition of magnetic discovery being dispatched, observations be also instituted at each fixed station, in correspondence with, and on a plan concerted with the commander of, such expedition.

As regards the second branch of the subject referred to them, viz. the proposal of an Antarctic voyage of magnetic research, they are of opinion, as already generally expressed, that such a voyage would be, in the present state of the subject, productive of results of the highest importance and value; and they ground this opinion on the following reasons:

Firstly. That great and notorious deficiencies exist in our knowledge of the course of the variation lines generally, but especially in the Antarctic seas, and that the true position of the southern magnetic pole or poles can scarcely even be conjectured with any probability from the data already known.

Secondly. That our knowledge of the dip throughout those regions, and the whole southern hemisphere, is even yet more defective, and that even such observations of this element as could be procured at sea, still more by landing on ice, &c., would have especial value.

Thirdly. That the intensity lines in those regions rest on observations far too few to justify any sure reliance on their courses over a large part of their extent, and over the rest are altogether, conjectural. Nevertheless, that there is good reason to believe in the existence and accessibility of two points of maximum intensity in the southern as in the northern hemisphere, the attainment of which would be highly interesting and important.

Fourthly. That a correct knowledge of the courses of these lines especially where they approach their respective poles, is to be regarded as a first, and indeed, indispensable preliminary step to the construction of a rigorous and complete theory of terrestrial magnetism.

Fifthly. That during the progress of such an expedition, opportunities would of necessity occur, (and should be expressly sought) to observe the transitory fluctuations of the magnetic elements, in simultaneous conjunction with observations at the fixed stations and in Europe, and so to furnish data for the investigation of these changes in localities very unlikely to be revisited for any purposes, except those connected with scientific inquiries.

Your committee, in making this report, think it unnecessary to go into any minute details relative to the instruments or other material required for the proposed operations, still less into those of the conduct of the operations themselves. Should such be required from them, it will then be time to enter further into these and other points, when the Committee will more readily, devote themselves to the fullest consideration of the subject.

“J. F. W. HERSCHEL,
“Chairman of the Joint Physical and Meteorological Committee.”

Resolutions of the Council.

1. That this report be received and approved.
2. That the council, deeply impressed with the importance of the scientific objects which might be attained by an Antarctic expedition, particularly by the institution of magnetic observations in southern regions, do earnestly recommend that Her Majesty’s Government be pleased to direct the equipment of such an expedition.
3. That the imperfect state of our present knowledge of the amount and fluctuations of the magnetic elements, renders the establishment of fixed magnetical observatories, for a limited time, at various points of the earth’s surface, highly desirable, particularly in Canada, St. Helena, Van Diemen’s Land, and Ceylon, and at the Cape of Good Hope, and that the council do earnestly recommend Her Majesty’s Government to cause such observatories to be established.
4. That a deputation, consisting of the president, treasurer, and secretaries of the society, Sir John F. W. Herschel, the chairman, and Major Sabine and Mr. Wheatstone, the secretaries of the Joint Committee of Physics and Meteorology, be requested to communicate the above resolutions to Lord Melbourne, and to urge on the Government the adoption of the measures therein proposed.