318 MR. FARADAY ON THE GROUPING OF PARTICLES, &C. 
covered by a plate of glass, is a necessary consequence of the arrangements 
there made, and tends to show how influential the action of the air or other in- 
cluding medium is in all the phenomena considered in this paper. No incom- 
patible principles are assumed in the explication given of the arrangement of 
the forces producing the two classes of effects in question, and though by varia- 
tion of the force of vibration and other circumstances, the one effect can be 
made, within certain limits, to pass into the other, no anomaly or contradiction 
is thus involved, nor any result produced, which, as it appears to me, cannot 
be immediately accounted for by reference to the principles laid down. 
Royal Institution , 
March 21, 1831. 
