PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 977 



preventing them from settling, and thus protects the boiler from 

 incrustation." 



From the discussion which followed, it was apparent that the 

 members present thought many more experiments would be 

 required to settle definitely the value of electricity in preventing 

 incrustation. 



H. F. Walling, Esq., presented the following paper, which 

 was read by title : 



The Measure of Force ii^r Moving Bodies. 



The determination of the quantity of force which is associated 

 with a body in motion has engaged the attention of mathematicians 

 and philosophers since the day of Newtdu and Leibnitz, who 

 originated a remarkable controversy on the subject, which was 

 energetically carried on for many years, and, indeed, seems not 

 to be fully settled, even at the present time. 



Although the positions taken by those celebrated disputants 

 and their respective followers were widely different, it is to be 

 observed that neither controverted the experimental and practical 

 results obtained by the other. 



Sir John Playfair, therefore, having given the subject most full 

 and careful attention, sums up his history of the controversy by 

 remarking that, "In reality, the two parties were not at issue on 

 the question ; their positions, though seeemingly opposite, were 

 not contrary to one another ; and after debating for nearly thirty 

 years, they found out this to be the truth." Finding that the 

 difference consisted in the definitions rather than in the facts it v>'as 

 quite generally decided, about the middle of the last century, that 

 since force is the agent by which motion is produced, its quantity"- 

 should be measured by the '•'■ quantity of motion'''' in the moving 

 body, which is proportional in bodies of equal weights to the 

 velocities of the bodies. In unequal bodies, the product of the 

 mass into the velocity affords a means of comparison. This pro- 

 duct is also called the momentum of a moving body. 



On the other hand, several eminent men of the present day 

 appear to advocate a reversal of this decision, and the adoption of 

 the measure proposed by Leibnitz, called by him ''■vis viva''"' or 

 living force of a moving body, namely, its mass into the square of 

 its velocity. This question is by no means an unimportant one, 

 and, upon its decision, many of the discoveries which are rapidly 

 [Am. Inst.] JJJ 



