STATEMENT OF MAYEn's ARGUMENT. 389 



continue in motion, without the necessity for any external 

 motive force. The discovery of such a perpetual motion was, 

 indeed, worthy of every effort. It would be as valuable as 

 the bird which lays the golden eggs ; for by its means labour 

 would be performed, and money made in abundance without 

 any expenditure. 



A mass of facts, hitherto unintelligible, have had much 

 light thrown upon them by a more correct view of natural 

 forces, for which we are indebted to a physician, Dr. Mayer, 

 of Heilbronn, and which, by the investigations of the most 

 eminent natural philosophers and mathematicians, has attained 

 a significance and importance scarcely to be foreseen. 



According to Dr. Mayer, forces are causes, in which full 

 application of the axiom must be found, that every cause 

 must produce an effect which corresponds and is equal to the 

 cause. Causa cequat effectum. Thus if a cause C produces 

 an effect E, then C = E. Should the effect E become the 

 cause of another effect e, then also E = e = C. In such a 

 chain of causes and effects no link, or part of a link, can ever 

 become nothing = nothing. Should a given cause C have pro 

 duced its corresponding effect E, then C ceases to exist, for 

 it has been converted into E. Consequently, as C passes into 

 E, and the latter into e, it follows that all these causes, as far 

 as relates to their quantity, possess the property of indestructir 

 bility, and to their quality that of convertibility. In number- 

 less cases we see a motion cease, without its usual effects 

 being produced, such as lifting a weight or load ; but as the 

 force which has caused the motion cannot be reduced to 

 nothing, the question arises, what form has it assumed. Ex- 

 perience gives the answer, by showing that wherever motion 

 is arrested by friction, a blow, or concussion, heat is the re- 

 sult. The motion is the cause of the heat. 



The rapid friction of two plates of metal can raise their 

 temperature to redness, and cause the ebullition of water if 

 the friction takes place below its surface. In like manner. 



