Chase.] 492 [December. 



molecular equilibrium, that the numerical equivalent of the magnetic 

 force is therefore equal and opposite to that of the disturbing force, 

 (+ M ^ + D), and that all the phenomena of terrestrial magnetism 

 result from tidal and thermal changes in terrestrial gravitation. 



Sullivan* and Reinsch'j' have pointed out the effect of musi- 

 cal vibrations upon the magnetic needle, and I have shown the 

 controlling influence of a purely mechanical polarity. | A care- 

 ful examination of the polarizing thermal and rotation currents,§ 

 will show that the spirals, which they have a tendency to produce, are 

 quasi horizontal cyclones, one set flowing in a nearly constant direc- 

 tion along the magnetic meridian, and the other towards the momen- 

 tarily shifting solar meridian. The communication of " Torricelli" 

 referred to but one or two of the relations under which these eddies 

 may be viewed ; there are others, some of which are perhaps even 

 more curious ; and, from the examinations which I have already made, 

 I have deduced the following theses : 



I. The daily magnetic variations, though subject to great disturb- 

 ances, at different hours, show an average approximation to the dif- 

 ferences of the gravitation-tidal currents. 



Hours from Mean, .... Ih. 2h. 3h. 



Means of Theoretical Ratios, . . .500 .866 1. 

 " " Observed '' . . . .563 .865 1. 



II. Marked indications of an accelerating force are discoverable in 

 the magnetic fluctuations, especially during the hours when the sun 

 is above the horizon. 



Hours from Mean, . . . . Ih. 2h. 3h. 

 Mean Ratios of Hourly Tidal Differences, 100 73 27 



" ^' " Squares of Hourly Mag- 



netic Differences, 100 74 26 



See also Thesis V. 



III. There are lunar-monthly barometric and magnetic tides, which 

 may be explained by differences of weight or momentum, || occasioned 

 by the combined influences of solar and lunar attraction, and terres- 

 trial rotation. 



IV. The solar-diurnal variations of magnetism between noon and 



* See De la Rive's Electricity, v. ii, p. 6.35. t Phil. Mag. [4J, 13, 222. 



t Ante, p. 359. § Ibid., p. 367 sqq. 



II I believe there can be no weight without some degree of momentum. See 

 Proc. A. P. S., vol.ix, p 357. 



