Royal Society. 385 



value, or about -^y - of the total force, it is but little greater 

 than Helmholtz found in the vibration-ratios for the first over- 

 tone of a series of tuning-forks (5 '8 to 66 times the funda- 

 mental), while it is much less than the daily fluctuation in the 

 terrestrial magnetic force, which appears to be intimately con- 

 nected with the joint action of atmospheric elasticity and solar 

 differential tidal attraction. 



The coefficient of atmospheric specific gravity, 4, suggests the 

 ratio of the length of a sonant aerial column to that of an equi- 

 valent sonorous wave, as well as the time of a complete oscillation 

 of each magnetic pulse. During each vibration, from a maximum 

 of condensation across the position of equilibrium to minimum, 

 or vice versa, the effect produced by any constant force would be 

 four times as great as during the half oscillation from either ex- 

 treme to the point of equilibrium. The ratios of wave-velocity 

 to elasticity and density, and of revolution to distance from the 

 centre of motion, point to various experiments upon the relations 

 of magnetic capacity to tenacity in iron, and of magnetizing- 

 power to specific gravity or to specific heat* in coils of different 

 metals. If such experiments should show any intimate con- 

 nexion between elasticity and specific magnetism (a result which 

 it does not seem unreasonable to anticipate), some of the mys- 

 tery in which an interesting physical fact is now shrouded will 

 be happily dispelled. 



XLV. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 307-] 



March 5, 1868.— John Peter Gassiot, Esq., Y.P., in the Chair. 



THE following communication was read : — 

 "On Governors." By J. Clerk Maxwell, M.A., F.R.SS.L. &E. 

 A governor is a part of a machine by means of which the velocity of 

 the machine is kept nearly uniform, notwithstanding variations in the 

 driving-power or the resistance. 



Most governors depend on the centrifugal force of a piece con- 

 nected with a shaft of the machine. When the velocity increases, 

 this force increases, and either increases the pressure of the piece 

 against a surface or moves the piece, and so acts on a break or a 

 valve. 



* The specific heats of iron, cobalt, and nickel are nearly the same, being 

 each about twenty-seven times that of hydrogen. Recently discovered cos- 

 mical affinities of hydrogen and iron, and the ratio between solar and ter- 

 restrial superficial gravitation, may perhaps sometime lead to the recogni- 

 tion of a significance in relations which would now be generally regarded 

 as fanciful and accidental. 



