ON THE KEW MAGNETOGRAPHS. 325 



ever, remark, that since it has been found that the winter storms travel east- 

 ward, it would be well to have some observers in Nova Scotia, Labrador and 

 Newfoundland. One at St. John's, Newfoundland, would be desirable. As 

 to the time of commencing, we can scarcely perhaps secure a perfect organi- 

 zation prior to the beginning of 1853. 



" I remain, very respectfully, your friend and servant, 



" Joseph Henry, Secretary^ 

 Col. E. Sabine. 



Report on the Kew Magnetograplis. By Colonel Sabine, R.A. 



At the request of the Council Colonel Sabine gave a brief account of the 

 experimental trial now making at the Kew Observatory of Mr. Ronalds's 

 Instruments for the self-registry of the Variations of Terrestrial Magnet- 

 ism by means of Photography. 



The general principle of these instruments and tlieir mechanical details 

 have been already described at former Meetings, and have been printed in 

 the Reports of the Association. But until instruments have been tested by 

 actual performance, no certain opinion of their fitness for the purposes for 

 which they were designed can be confidently pronounced ; and the super- 

 intending Committee at Kew have for some time past felt a rather anxious 

 desire, that the preparation of these instruments should reach the stage at 

 which a fair practical trial might be made of their efficiency, as a means of 

 recording the magnetic phecnomena in any part of the world where science 

 might require that they should be known. Before this could be done how- 

 ever, — before a correct estimate could be formed of the degree in which 

 they might be useful, either as auxiliaries, or as superseding the method of 

 observation previously in use, it was necessary that three instruments should 

 be provided, one for the variations of the declination, and two for those of 

 the horizontal and vertical components of the force. From the limited funds 

 which the British Association has had it in its power to appropriate to the 

 furtherance of the objects of the Kew Observatory, it had been just barely 

 possible to complete two of the three instruments between the years 1846 

 and 1850, and the third must yet have been waited for, had not a resource 

 presented itself in the Government grant in 1850 placed at the disposal of 

 the President and Council of the Royal Society, to be applied in aiding the 

 progress of the experimental sciences. A portion of this grant was obtained, 

 and the three instruments being at length by its aid completed, Mr. Ronalds, 

 with the sanction of the superintending Committee, proposed to the Council 

 of the Royal Society that the instruments should be subjected to an experi- 

 mental trial by being worked precisely as in an observatory, for a period of 

 six months (that period being considered as likely to be sufficient for a due 

 appreciation of their merits or deficiencies in reference to the present re- 

 quirements of magnetical science); and that every item of expense incurred 

 in carrying on the self-registry for that period should be carefully noted and 

 stated. This proposition having been approved by the Council of the Royal 

 Society, a grant of £100, for the purpose of carrying it into execution, was 

 made to Mr. Ronalds from the donation fund, the property of the Royal 

 Society. The six months' trial commenced in April last, and a full account 

 of its results will be presented to the Royal Society ; meantime the Council 

 of the British Association have deemed that a brief account of the nature 

 of the trial might not be unacceptable to its members. 



