1864.] 



President's Address. 



503 



a Circular which, with the concurrence of the Council, I addressed to 

 them. This correspondence having been submitted in a printed form 

 through the proper channel to the Secretary of State for India, the pro- 

 ceedings proposed by Colonel "Walker for carrying out the experiments 

 have been officially sanctioned. An application to the Eoyal Society 

 for a loan of two of the pendulums which had been previously employed 

 in similar experiments, with their attendant clock, has been acceded to ; 

 and a Yacuum Apparatus convenient for transport, in which the pendu- 

 lums may be vibrated at the Indian stations, has been constructed at the 

 Kew Observatory. Captain Basevi, of the Eoyal Engineers, appointed 

 to conduct the experiments in India, has resided for some weeks at Kew 

 for the purpose of making himself practically acquainted with the instru- 

 ments, and the mode of experimenting with them. Circumstances having 

 obliged Captain Basevi to proceed to India before the base observations 

 could be made at Kew, these have been undertaken by the Kew Obser- 

 ving Staff, and will be carried on in an apartment arranged for the pur- 

 pose, which will be hereafter available for the verification of the same 

 pendulums on their return from India at the close of the operations ; and 

 will, moreover, supply a convenient locality for future occasions of a 

 similar kind, as well as for the comparison of the pendulums of other 

 countries. We may not unreasonably anticipate that such experiments 

 may henceforward be regarded as an appropriate accompaniment to the 

 measurement of arcs in all parts of the globe. 



I am glad to be able to add that Colonel Walker has also directed 

 that the Indian Survey should be provided with instruments for deter- 

 mining the absolute values of the three magnetic elements at the Indian 

 stations. We may thus hope to obtain a further investigation of the 

 (apparent) systematic anomaly in the direction of the lines of magnetic 

 force in the central parts of India, which is so remarkable a feature in 

 the admirable magnetic survey of that portion of the British dominions 

 executed by the Messrs. de Schlagintweit. 



Whilst on the subject of terrestrial magnetism, I may be permitted 

 to notice that, in a paper presented in the last session, I have called 

 the attention of the Society to a very remarkable feature, made known 

 by the comparison of the disturbances of the magnetic declination in 

 England, and at stations nearly in the same latitude in the eastern parts 

 of Asia. The days in which such phenomena occur are almost without 

 exception the same in both localities ; the hours (of absolute time) at 

 which the maxima and minima of disturbances characterized by a com- 

 mon type take'place are, within very small limits, also the same ; but 

 the direction in which the magnet is at the same moment deflected in 

 these otherwise most accordant phenomena is systematically opposite in 

 England and in eastern Siberia. I attach of course far more import- 

 ance to the fact itself than to the hypothesis which guided me to its 

 anticipation, and thence to its discovery ; still, an hypothesis which has 



