concerned in the Phenomena of ordinary Electricity, fyc. 123 



of the labourers were set on fire when exposed to the focus, 

 although these rays had to pass through twenty-five feet depth 

 of water. Captain Scoresby succeeded in burning bodies by the 

 sun's rays passed through a lens of ice, the ice itself remaining 

 unmelted. Heat is held combined in voltaic electricity, as ap- 

 pears from the fact, that a thin platinum wire may be melted by 

 a current which has passed through tinfoil immersed in a free- 

 zing mixture. Those who maintain the identity of light and 

 heat will deny that these facts prove anything. Their effect 

 woidd certainly fail if it can be satisfactorily explained why a 

 sun-beam, by falling on the moon, is so far altered, that when 

 reflected to the earth and concentrated 3000 times by our spe- 

 cula, the light has no effect on the most sensible thermometers, 

 or even on a thermo-multiplier*. 



That electricity is combined with light in the sun's beam by 

 some such force as is here presumed to hold the elementary con- 

 stituents of the electric fluid together, is rendered strikingly pro- 

 bable by an experiment of Matteucci. When the sun's rays are 

 made to fall on a perfectly dry glass plate, the latter becomes 

 electrical ; a second plate on which the light falls after passing 

 through the first does not become so, although there is little 

 diminution of the light. That the effect is due to the electricity 

 of the beam, and not to excitement of the glass by heat, is shown 

 by the failure of any effect on the second plate, and also by the 

 fact that heating by fire has no such power. The electric fluid 

 is carried forward in the beam by the coercive power alluded to, 

 yet is so far obedient to the law of non-conductors that it is in- 

 tercepted by the first glass plate, and does not pass to the second. 

 This, at least, seems the most probable explanation ; and, in such 

 recondite subjects, probability is our chief guide. 



It is to be remembered that chemical attraction or affinity is 

 attributed to electricity in direct terms by the philosophers of 

 the present day. They speak of combinations of electricity with 

 hydrogen, oxygen, and other bodies, and found systems on the 

 existence of such combinations, in which cases the affinity must 

 be mutual. If they are warranted in attributing affinity to in- 

 tegral electricity, I am not less so in attributing the same power 

 to its constituents. 



All these considerations show, that in my assumption of a 

 coercive power which preserves the integrity of the electric fluid 

 by holding its constituent elements in union, there is nothing 

 irreconcileable or repugnant, inasmuch as a similar power appears 

 to act on the heterogeneous elements of other imponderable 

 matter. 



If it be admitted that the electric fluid consists of heterogc- 

 * Ginulin, vol. i. p. 166. 



