Prof. Matteucci on the Origin of Muscular Power. 289 



the action of light might result from the same general tendency 

 to effect a decomposition of united molecules. 



Heat may in some cases produce the same chemical result as 

 light, or the actinic rays generally. For example, it explodes 

 the mixture of chlorine and hydrogen. But the effect must be 

 ascribed to the repulsive action of the heat-pulses taken up by 

 the molecular atmospheres at considerable depths below their 

 surface j whereas the separating action of the actinic rays is pro- 

 bably due to a movement of the electric aether effected at the 

 surface of the atmospheres. It is questionable whether the 

 actinic rays are capable of imparting any sensible polarization to 

 molecules. In this respect their tendency is the reverse of that 

 of heat, viz. to impart a negative instead of a positive polarity ; 

 for their impulses act directly upon the sether of the molecular 

 atmospheres, but the heat-impulses, as we have seen, act indi- 

 rectly, producing expansion. The distinction is the same, es- 

 sentially, as that taken between the two modes of action of the 

 external impulses exerted by electric currents (/. c. p. 280), — the 

 one, analogous to light, developing magnetic currents in groups 

 of molecules, and the other, like heat, determining a reverse 

 polarization of molecules, compound or simple, by an indirect 

 expansive action. 



XXXVII. On the Origin of Muscular Power. 

 By Professor C. Matteucci. 



To the Editors of the Philosophical Magazine and Journal. 



Royal Institution, 

 Gentlemen, September 24, 1866. 



I BEG to forward you the enclosed letter just received from 

 Professor Matteucci. It will doubtless be read with atten- 

 tion by many who are now interested in the discussion of this 

 subject. 



I am, Gentlemen, 



Yours truly, 



E. Frankland. 



Firenze, September 9, 1866. 



Dear Professor Frankland, — The lively interest which I 

 felt in reading your memoir " On the Origin of Muscular Power," 

 forming the sequel of the beautiful experiments of Professors 

 Fick and Wislicenus, induces me to remind you of some conclu- 

 sions which I drew, a few years ago, from my electro-physiolo- 



Phil. Mag. S. 4. Vol. 32. No. 216. Oct. 1866. U 



