1881.] 57o [Chase. 



preciable portions of luminiferous setlier. Professor S. P. Thompson, in the 

 Philosophical Magazine for July, 1881,* makes the following noteworthy- 

 suggestion : 



" Matter has dimensions [M], Energy [ML^T^^], and Electricity Lm^ 

 L^ T-^J. The latter value is obtained from a consideration of the Law of 

 Coulomb, that Q X Q ^ L^ = force = [ML T-^] ; whence 



Q = [(ML3T-2)i]. 



But the dimensions of self-attractive matter may be similarly considered 

 by Newton's Law that — M.M -^ L^ — force = [M L T-^], whence 



M=:[-L3T-2]. 



And if this value be put in place of M in the dimensions of Q above, 

 we get Q = ry — 1 (L^ T-^)! a quantity whose dimensions differ only from 



those of M in being prefixed by the imaginary quantity j/ — 1. This seems 

 to indicate an important relation. " 



99. Change of State. 



In the Philosophical Magazine for July, 1881, Professor J. H. Poynting 

 discusses "Change of State ; Solid-Liquid." He shows that it follows 

 from his "mode of regarding the subject, that, if in any way the ice can 

 be subjected to pressure while the water in contact with it is not so sub- 

 jected, then the lowering of the melting point per atmosphere is about 11^ 

 times as gi'cat as when both are compressed" (p. 34). In Hei'schel's 

 hypothesis of nebular " subsidence " a similar action is implied, the nebu- 

 lous or sethereal atmosphere corresponding to the uncompressed water, 

 and the subsiding particles, under the gravitating pressure, corresponding 

 to the compressed ice. In a former study of potential energy (Proc. Soc. 

 Phil. Amer., xvii, 98), I showed that, under such circumstances, "the in- 

 crease of radial velocity would be sufficient to produce orbital velocity in 



the periphery of a stationary nebula, when i/n = |/2 (]/n-l), and n = 



2 

 ^ = 11.656854." The important bearing of this relation upon plane- 



tary positions was also shown at the same time. 



100. Earth's Photodynamic Condensation. 



JjQt ts = time in which solar superficial gravitation would communicate 

 the velocity of light, or time of solar half-rotation ; ^ = Jupiter's orbital 

 time ; r^ = Earth's semi-diameter ; r^ = 338.2183 r^ = Earth's synchro- 

 nous radius, or distance at which a particle would revolve about Earth, 

 synchronously with Earth's revolution about Sun, 



Then r, : r.^ : : t^ : t^. 



This gives 12.81 days for tj^, or 25.62 days for Sun's rotation, which is J 



*Foot-note page 17. 



