No. 3. Memorandum containing extracts from the Minutes of the Kew Committee relating to Magnetic Reductions, and containing also an estimate of the probable Expense of carrying out the list of suggestions (paper No. 2). MY DEAR SIR, Kew Observatory, 4th March, 1870. In accordance with the wish expressed at the last Meeting of the Kew Committee for full information regarding the present state of the magnetic reductions, I beg to send you the following statement: The first extract bearing on this subject is one from the Report of the Kew Committee to the Aberdeen Meeting of the British Association. It is as follows: "As the staff of assistants at the Observatory is not sufficiently large to "undertake these tabulations, General Sabine has undertaken to have the "results tabulated at Woolwich for every hour." In a scheme for the working of the Observatory after it became the central Observatory of the Meteorological Committee, I suggested that it would be very desirable to undertake the tabulation and reduction of the magnetic curves. Simultaneously with this scheme, their Report to be presented to the Meeting of the Association in 1867 was discussed by the Kew Committee, and in the Report the following statement occurs : "The magnetic curves produced at Kew previously to the month of "January 1865 have all been measured and reduced, under the direction of "General Sabine, by the staff of his office at Woolwich; and the results of "this reduction have been communicated by General Sabine to the Royal Society in a series of interesting and valuable memoirs. It is now pro"posed that the task of tabulating and reducing these curves since the above "date be performed by the staff at Kew working under the direction of Mr. "Stewart." In accordance with this resolution, the magnetic tabulations were proceeded with as fast as the funds at the disposal of the Observatory would allow, and the exact progress made was from time to time reported to the Committee. In my Report to the Meeting of the Kew Committee held on June 18, 1869, the following passage occurs : "In the present organization of the Observatory, it is the surplus funds. "that are devoted to magnetic reductions; but it will hardly be possible be"fore the yearly accounts are closed to state the probable amount of the "surplus. "It is, however, imagined that if the probable surplus for the year "1869-70 be anticipated and devoted to tabulation while the summer wea"ther lasts, then before the end of next winter session the reductions will "be very far advanced for all of the three magnetic elements." At the same Meeting the following resolution was passed: Resolved,-"That Mr. Balfour Stewart be authorized to apply the sur"plus funds in his hands to the tabulation and reduction of the magnetic "photographic records; and that he be requested to have the work done "with as much rapidity as is consistent with accuracy-the final reduction "to include both monthly and annual means, but in the first instance the "phenomena of the disturbances from 1863 to 1870 to be proceeded with. "In reference to Mr. Balfour Stewart's proposal that a more intimate "comparison between solar and magnetic records be made, it was resolved "that he be requested to prepare such a comparison for one magnetic cle"ment, for a whole period of solar disturbance, for the consideration of the "Committee." From all these extracts it will, I think, appear that the Committee considered that they would have funds sufficient to tabulate and reduce the magnetic curves since the beginning of 1865, the date at which Sir E. Sabine left off tabulating, and that any resolution having reference to curves of a previous date did not contemplate any retabulation of such curves. I conceive, therefore, that at present I am under obligation to tabulate and reduce the curves obtained since the beginning of 1865, the Committee acting on the supposition that the funds which accrue to the Observatory from various sources are sufficient for this purpose. If, however, the Committee should consider that, in addition to this, it would be desirable to systematize the whole Kew results after the method indicated in the suggestions by me which accompany this letter, it would be quite possible to accomplish this work before 1872, and to do so without materially interfering with the work of the Observatory; but it would require additional funds for the purpose; in fact, the question resolves itself into one of expense. The following estimate, prepared by Mr. Whipple, and revised by me, will give a tolerably good idea of the probable expense of doing this: (e) Purchase of two new Tabulating instruments and fit- Measurement of curves to Too of an inch from Jan. 1, 1858, to Dec. 31, 1864. Subsidiary measurements Copying out and systematizing results Extraction of disturbances Paper and forms This sum would probably enable all these suggestions to be complied with, except those relating to the means connected with the lunar-diurnal variations. The production of such means since 1865 will, of course, form part of the reductions at present in hand, and it would be very easy to give the tables such a shape as to exhibit a classification according to the relative position of the sun and moon. If the results of this proved sufficiently valuable, the same classification might be afterwards extended to the results previous to 1865, provided the details of such results have been obtained and preserved by means of the outlay of £472 14s., as mentioned above. This particular form of reduction does not appear so pressing; and as it would cost £130 to recast the individual results previous to 1865 into the precise form of lunar tables mentioned in the suggestions, this matter may be allowed to wait. But the other matters mentioned in these suggestions are, I think, of greater importance, more especially as, in the very valuable paper of results produced by Sir E. Sabine, there would appear to have been contemplated an exhibition to the world of the most valuable and important facts derived from the Kew results, rather than an exhaustive reduction of the same (see paper No. 1). The Committee might, therefore, if the above outlay were incurred, exhibit the distribution over the various months of every year of the disturbed observations for the whole Kew series, and also exhibit the solar-diurnal variations of the horizontal and the vertical force. If it be allowable to devote to this purpose £100 which I have in hand from the Royal Society, it would so far lessen the expense, and in this case £400 might be regarded as the extreme limit of what would be incurred. I remain, J. P. Gassiot, Esq., Chairman of the Kew Committee. Yours very truly, B. STEWART. Extracts from Minutes of Kew Committee held at Burlington House on 9th March, 1870, Present Mr. Gassiot (in the Chair), Sir E. Sabine, Sir C. Wheatstone, Col. Strange, Dr. Miller, Mr. Galton, Mr. De La Rue, Mr. Spottiswoode. "Resolved, That the following work be executed at Kew, under the "superintendence of Mr. Stewart. "Current Work. "The work as defined in paragraph marked (a), page lii (General Sabine's "Memorandum). "Arrears of Work. "1st. Hourly tabulations from traces as defined in paragraph marked (b), page liii (Mr. Stewart's statement). "2nd. Separation of disturbances and solar-diurnal variations, para"graph (c), page liii. "3rd. Secular change and semiannual inequality, paragraph (d), page "liii. "These arrears to be executed in accordance with the estimate (e), page lv." It appearing that the only sum at the disposal of Mr. Stewart for back magnetic work was £100, Mr. Gassiot offered to supplement the difference required, provided the sum required from him did not exceed £400. Resolved unanimously,-"That the Committee accept with thanks the "munificent offer of their Chairman, and that Mr. Stewart be empowered "to proceed with the work on the understanding that the total cost shall "not exceed £500.” Accounts of the Kew Committee of the British Association from August 18, 1869, to September 14, 1870. Meteorological work done at extra hours Magnetical tabulations done by supernumerary assistants 875 3 0 50 O 1 75 16 9 71 9 6 46 2 11 33 18 0 RECOMMENDATIONS ADOPTED BY THE GENERAL COMMITTEE AT THE LIVERPOOL MEETING IN SEPTEMBER 1870. [When Committees are appointed, the Member first named is regarded as the Secretary, except there is a specific nomination.] Applications involving Grants of Money. That the sum of £600 be placed at the disposal of the Council for maintaining the establishment of the Kew Observatory. That the Committee for reporting on the Rainfall of the British Isles be reappointed, and that this Committee consist of Mr. Charles Brooke, Mr. Glaisher, Professor Phillips, Mr. G. J. Symons, Mr. J. F. Bateman, Mr. R. W. Mylne, Mr. T. Hawksley, Professor Adams, Mr. C. Tomlinson, Professor Sylvester, Dr. Pole, and Mr. Rogers Field; that Mr. G. J. Symons be the Secretary, and that the sum of £50 be placed at their disposal for the purpose. That the Committee on Underground Temperature, consisting of Sir William Thomson, Dr. Everett, Sir Charles Lyell, Bart., Mr. J. Clerk Maxwell, Professor Phillips, Mr. G. J. Symons, Mr. Balfour Stewart, Professor Ramsay, Mr. Geikie, Mr. Glaisher, Rev. Dr. Graham, Mr. E. W. Binney, Mr. George Maw, Mr. Pengelly, and Mr. S. J. Mackie, be reappointed with the addition of the name of Mr. Edward Hull; that Dr. J. D. Everett be the Secretary, and that the sum of £150 be placed at their disposal for the purpose. That the Committee on the Thermal Conductivity of Metals, consisting of Professor Tait, Professor Tyndall, and Dr. Balfour Stewart be reappointed; that Professor Tait be the Secretary, and that the sum of £20 be placed at their disposal for the purpose. That the Committee on Tides, consisting of Sir W. Thomson, Professor Adams, Professor W. J. M. Rankine, Mr. J. Oldham, Rear-Admiral Richards, and Mr. W. Parkes be reappointed, and that the sum of £100 be placed at their disposal for the purpose. That the Committee on Luminous Meteors, consisting of Mr. Glaisher, Mr. R. P. Greg, Mr. Alexander Herschel, and Mr. C. Brooke be reappointed, and that the sum of £30 be placed at their disposal for the purpose. That Mr. Edward Crossley and Rev. T. W. Webb be a Committee for discussing Observations of Lunar Objects suspected of change; that Mr. Crossley be the Secretary, and that the sum of £20 be placed at their disposal for the purpose. That Sir J. Herschel, Bart., and Professor Erman be a Committee for the purpose of procuring the Recomputation by Professor Petersen of the Gaussian Constants for 1839, so as to make the additional available observations, and that the sum of £50 be placed at their disposal for the purpose. That Professor Balfour Stewart, Mr. Latimer Clark, and Mr. C. T. Varley be a Committee for the purpose of investigating the best method of Measuring Electrical Capacity, and of constructing Standard Measures of Capacity; that Prof. Balfour Stewart be the Secretary, and that the sum of £20 be placed at their disposal for the purpose. That Professor Sir William Thomson, Mr. J. Clerk Maxwell, and Professor Fleeming Jenkin be a Committee for the purpose of investigating the bes method of measuring differences of Electrical Potential, and issuing a Stan_ |