Chase.] 588 [jan. 19, 



vera causa of Sim's equatorial acceleration. Jupiter's influence upon har- 

 monic masses and positions (Notes 313, etc.), and the close approximation 

 of the photic radius (Note 345) to Jupiter's projectile centre of linear os- 

 cillation, show that there are activities, at various distances from the Sun, 

 which should be considered in discussing the conservation of solar energ}% 

 The centrifugal force to which Siemens refers is 'by no means limited to 

 Sun's surface ; at Laplace's limit (36.36r„), at the photic radius (689/'J, 

 and at the solar modulus of light (689'V„), tliereare important rotating and 

 consequent centrifugal tendencies wliich have been almost wholly over- 

 looked. Darwin's discussions of terrestrial "viscosity" furnish many sug- 

 gestive hints for an investigation which, as I fully believe, will help greatly 

 to extend Laplace's views of universal stability. No one, probably, would 

 think of limiting the centrifugal force of terrestrial rotation to Earth's sur- 

 face, nor even to its atmospheric modulus ; there is great likelihood that 

 an appreciable atmosphere may extend even beyond Laplace's limit (G.G/'j), 

 all portions within that limit rotating synchronously with Earth, while all 

 portions beyond the limit are subject to combined influences of rotation 

 and revolution. Sun's asthereal modulus extends to more than 73 times 

 Neptune's semi-axis major, and if we suppose that to be the limit of 

 .sethereal centrifugal tendency, we have an available velocity which is 089 

 times as great as the velocity of light, If we suppose, still further, that 

 Laplace's velocity of gravitating action, more than 100,000,000«;^ {Mee. 

 Celeste, X, vii, 23), represents an actual physical velocity, we have a 

 radius of rotating influence which extends from the Sun as a centre to 

 more than 13000 times the distance of a Centauri. 



853. Motion in Perfect Fluids. 

 Siemens calls attention (Comptes Renclus, xcv, 1040), to the results of 

 Froude's Torquay experiments, which showed that a submerged body, 

 moving with uniform velocity in a perfect fluid, will meet no resistance 

 whatever. By "a perfect fluid" is meant a fluid free from viscosity or 

 quasi solidity, and in which no friction is caused by the slipping of its 

 j^articles cither over one another or over the surface of the body. If there 

 are any such fluids, the luminiferous aether is doubtless one. Ferrel's in- 

 vestigations have shown that the centrifugal force of rotation would draw 

 it entirely away from the poles, so that more viscous fluids, such as our 

 atmosphere, would serve, as Siemens says, as lubricators, to supply tempo- 

 rary vacua which would otherwise result from the slight lateral elastic 

 oscillations of the aether. These considerations, as well as those of the 

 foregoing note, open a new field for analytical research, which must be 

 thoroughly explored before final judgment can be passed upon questions 

 pertaining to the conservation of solar energy, the stability of the physical 

 universe, and the reproach of thermodynamics. 



854. Centripetal Transformation of Radiations. 



When particles or bodies are moving in circular orbits, under the in- 

 fluence of central forces, the centripetal and centrifugal forces are in equi- 



