No. XII.]' APPENDIX. 207 



action and reaction. Time is, therefore, a strictly material property. 

 Without matter we could not have time, and even with matter the pheno- 

 menon of time requires for its manifestation some new attraction to over- 

 come an old one. The tendency of the action of the new attraction to 

 overcome the old one is called the commencement of a unit of time ; the 

 actual performance of the new attraction, after the destruction of the old 

 one, or the actual resistance of the new attraction by the old one, is called 

 the termination of a unit of time. The absolute performance or resistance 

 of a new action that is, its commencement and termination constitutes 

 an event, and, according to the energy of this event, it is said to be of 

 shorter or longer duration." P. 161. 



Having thus shown time to be a material property, its abstract idea to 

 be that of resistance to an action, and having treated of the instruments 

 for its measurement, he next reviews the effects produced by matter when 

 under the influence of conflicting forces. 



" Having seen the conditions of matter in a quiet state, we have next 

 to examine its properties when in commotion ; and the sciences of commo- 

 tion, or rather of actions and reactions, which now fall under our notice, 

 are respectively those of heat, light, sound, and scent. All these terms 

 are abstract ideas of material actions and reactions, and there is no 

 imponderable or essence in either heat, light, sound, or scent, to which 

 matter owes its power of being hot, illuminated, noisy, or odoriferous." 

 P. 172. 



The first of these sciences is that of heat, which he believes to consist 

 in a peculiar vibrating condition of bodies, caused by the conflict of new 

 attractions seeking to overcome former ones. 



" We find, if we take a review of all sources of heat, the phenomenon 

 is owing to some new attraction acting on a body, the particles of which 

 are held together by former attractions. A hot body is, therefore, a body 

 whose attractions are interfered with by other attractions, and heat is the 

 abstract term of this disturbance of attractions in a particular manner." 

 P. 173. 



The sources of heat next come under consideration : and, firstly, those 

 of the heat exhibited during electrical phenomena ; then a much more 

 familiar and important source. 



" The next source of heat after that derived from new attractions 

 producing electrical forces, is that derived from the attraction of chemical 

 affinity. The phenomenon of heat is not manifested by the chemical union 

 of any two bodies, if the combination takes place without being impeded 

 by the other attractions, or if the other attractions are quietly destroyed. 

 If the combination takes place with great energy, however, the rapid ten- 

 dency to the destruction of attractions, reacting against the desire for 

 maintaining them, gives rise again to the phenomenon called heat. In the 

 combustion of coals, the rapid desire for the particles of coal to unite with 

 the oxygen of the air, acting upon the desire of the particles to maintain 

 their old attraction of cohesion, causes that heat to be manifested which so 

 comforts and cheers us in our dreary winter's night." P. 176. 



After describing the other sources of heat, and treating of its pro- 

 perties and conduction, &c., which are clearly and minutely detailed, he 

 passes to light and sound, which, like heat, depend on certain classes of 

 vibrations, perceptible by certain of our organs of sense. Odour he supposes 



