( 708 ) [Oct., 



REVIEWS. 



EADIATION.* 



A not very enlightened sceptic once remarked that he doubted 

 " whether there was any other God but motion." Had he not igno- 

 rantly mistaken effect for cause, and if he had, instead, uttered a doubt 

 whether there was any physical force other than motion, he would have 

 been nearer the truth, and would have expressed the view of the most 

 advanced thinkers of our time. For every day it is becoming more 

 apparent that the various forces or phenomena known to us as Heat, 

 Light, Electricity, &c, all result from the more or less rapid motion of 

 matter in a more or less attenuated form. Thus, when we hear of 

 light travelling at the rate of 192,000 miles per second, reaching our 

 earth in about eight minutes after it has left the sun, we are not to 

 suppose that any special force is being employed, differing from that 

 which conveys the sensation of heat from a body of elevated tempera- 

 ture to our persons, or from that which causes the air, agitated by the 

 vibrations of a sonorous substance, to strike against the tympanic 

 membrane of the ear, and produce the impression of sound. All these 

 manifestations, light, heat, and sound, are believed to be simply the 

 effects of the more or less rapid vibrations of atoms of matter variously 

 grouped, communicated to organs of the body differently constituted 

 to receive those divers impressions. 



When any hard substance is submitted to violent friction, heat, 

 sound, and perhaps electricity, may be the result of the motion of its 

 molecules. In the case of sound being produced, the atoms of the 

 resonant substance first begin to vibrate, then they impart motion 

 to the molecules of the circumambient air, and this being agitated 

 in waves reaches the tympanic membrane, and there produces the 

 effect which we know as " sound," an effect which is passed onwards 

 through the complicated structure of the ear and the auditory nerve to 

 the brain, whereby the mind is rendered conscious of its existence. 

 A similar motion of particles, conveyed with or without the medium of 

 the air, to the nerves of touch, causes the phenomenon of heat, which 

 may be communicated to the brain and be thus rendered conscious, or 

 it may be arrested at the surface of the body, and affect only the 



* ' On Eadiation.' The Kede Lecture delivered in the Senate House, before 

 the University of Cambridge, on Tuesday, May 16th, 1865. By John Tyndall, 

 F.E.S., Professor of Natural Philosophy in the Royal Institution, and in the Royal 

 School of Mines. London : Longmans. 



' The Phenomena of Radiation, as Exemplifying the Wisdom and Beneficence 

 of God.' (Actonian Prize Essay.) By George Warington, F.C.S. London : 

 William Skeffington. 



* Heat Considered as a Mode of Motion.' By John Tyndall, F.R.S., &c. 

 Second Edition, -with Additions and Illustrations. London : Longmans. 



