1865.] \\l [Chase. 



Mr. Chase made a communication on the correhition of 

 gravity with the vertical deflection of the needle. 



A somewhat critical survey of the anomalies presented by the 

 magnetic inclination, to which I referred in a former article (Proc. 

 Am. Phil. Soc, April 21, 1865), has given me renewed reasons for 

 regretting the want of a complete record of the investigations on 

 ■which Prof. Secchi based his conclusion, that all "the phenomena 

 hitherto known of the diurnal magnetic variations may be explained 

 by supposing that the sun acts upon the earth as a very powerful 

 magnet at a great distance."* As I know of no magnetic law which 

 will account for those anomalies, I propose briefly to describe them, 

 and to point out some relations between the gravitation currents and 

 the dip of the needle, as a sequel to my papers on the influence of 

 gravity upon the total magnetic force and the magnetic declination. 



Gen. Sabine's discussions have shown some important points of 

 difference between the magnetic disturbances at inter-tropical and 

 extra-tropical stations, the Cape of Good Hope being magnetically, 

 though not geographically, inter-tropical. In the third volume of the 

 Toronto Observations, and in Prof Bache's discussions of the ob- 

 servations at Girard College, projections of the daily and semi-an- 

 nual inclination-curves are given jf and Plate V, of the second volume 

 of the Hobarton Observations, contains a graphical representation of 



* Phil. Mag. [4] IX, 452. Faraday (Exp. Res. Ill, 493) states "that 

 the celebrated Prof. Gazzaniga, starting from his numerous experiments, 

 which demonstrate the influence of magnetism upon the same aerial 

 fluids, in a manner, therefore, difl'erent from that of Bancalari, was in- 

 duced to consider the sun, and all the other celestial bodies, as so many 

 enormous magnets, by which he established that attraction is merely one 

 effect of the magnetism of the great celestial masses placed at an enor- 

 mous distance, — an idea which reappeared in 1846 in Prussia, and in 

 1847 in France." 



While admitting the intimate relationship of magnetism and gravity, 

 I must dissent from the learned Professor's inference. For the evidence 

 appears irresistible, that the earth's magnetism is directly dependent on 

 the terrestrial gravitation of the thermally disturbed aerial currents, and 

 that it is only slightly affected by the perturbations of solar and lunar 

 gravitation, so that if we regard the relationship as a causal one, mag- 

 netism, rather than attraction, should be considered as the eflect. (See 

 Gauss' "General Theory of Terrestrial Magnetism," | 39, 40; Taylor's 

 Scientific Memoirs, II, 232.) 



f By the kindness of Prof. Henry, I have been permitted to refer to 

 the proof-sheets of the Fourth Section of Prof. Bache's Discussions. 



