Prof. Grove on the Correlation of Physical Forces. 77 



In the first lecture on motion the following original view of the 

 production of heat was taken. If one body move against or strike 

 another it communicates its motion to the latter, and stops while the 

 latter takes up the original motion ; and moves, not indeed quite 

 equal in amount to the original moving body, because the air or 

 other surrounding medium is set in motion, and thus conveys away 

 some of the initial force : if the second body be retained, or not per- 

 mitted to move in the same direction, it may still move in a different 

 one. Take for example two wheels, the circumference of which touch 

 each other : if the one be made to revolve it communicates motion 

 to the other which revolves in a different direction ; if, however, the 

 second be forcibly restrained or prevented from carrying on the 

 motion of the first, heat is produced : thus, though the motion appa- 

 rently ceases, still the effect of the initial force is rendered evident 

 in another form. The same thing occurs if two bodies, moving in 

 contrary directions, meet each other ; they, to a certain extent, arrest 

 or stop each other's motion, but to this extent they also become 

 heated. In the case of dissimilar bodies impinging on each other 

 electricity is produced as well as heat, but the more there is of the 

 one the less there is of the other force ; and neither in this case nor 

 in any other will the forces produced, whatever be their character, 

 reproduce the full amount of the initial force : thus the heat pro- 

 duced by friction could never, if applied to boil water, work a steam- 

 engine which would produce an equal amount of motion on the same 

 quantity of matter as that which originally gave rise to the heat ; 

 though the force is not destroyed, it is dissipated or subdivided in 

 direction. These considerations lead to the conclusion that force, 

 like matter, cannot be annihilated, but may go on subdividing itself 

 or changing its form for ever. Want of space prevents our going 

 through the experimental proofs adduced by Mr. Grove to support 

 his views. In each lecture one of the above forces was taken as the 

 initial force or starting-point, and it was shown experimentally how 

 the others were produced by it. 



The following is the order in which the subject was considered, 

 as stated in the syllabus printed for the members of the Institution 

 and other attendants of the lectures. 



Lect. I. — Monday, November 13th, 1843. — Introduction — Force — 

 Usual definition — Matter — Attraction — 'Motion — its connexion with 

 Light, Heat, Chemical Affinity, Electricity, Magnetism. Lect. II. — 

 Chemical Affinity — Ultimate conceptions regarding it — Transferred 

 or acting through a chain of particles — its connexion with the other 

 modes of force. Lect. III. — Heat and Light — Expansion or mutual 

 recession of Molecules — propagation of heat and light — Theories — 

 Specific Heat — Thermography — Photography — Relation to the other 

 modes of force. Lect. IV. — Electricity — Application of the term to 

 very different phenomena — Franklinic — Voltaic — Theories — Objec- 

 tion to hypothesis of fluids — Regarded as a mode of force and con- 

 nected with the other forces. Lect. V. — Magnetism — viewed as 

 an absorption of force — operative when conjoined with motion — 

 Magneto-Electricity. — All moving bodies magnetic in proportion to 



