Eqiiiltbrivm between Living and Dead Forces. 241 



latitude, they were much colder than those of Europe. This fact, 

 which could not be satisfactorily explained by the astronomic the- 

 ory of climates, engaged the attention of many naturalists, and 

 among others, of Halley. According to that celebrated philoso- 

 pher, a comet had formerly struck the earth obliquely, and chang- 

 ed the position of its axis of rotation. In consequence of that 

 event, the north pole, which had originally been very near to 

 Hudson's Bay, was changed to a more easterly position ; but the 

 countries which it abandoned had been so long a time, and so 

 deeply frozen, that evident vestiges still remain of its ancient po- 

 lar rigor. A long series of years would be required for the solar 

 action to impart to the northern parts of the new continent, the 

 climate of their present geographical position." 



Fortunately our knowledge of meteorology is now sufficiently 

 advanced to enable us to laugh at this crude explanation of a 

 change in the position of the terrestrial axis, resulting from the 

 concussion of a comet. 



Art. II. — On the Condition of Equilihrium between Living 

 and Dead Forces; by Robert Henry Fauntlerot, Civil 

 Engineer, New Harmony, Ind. 



It is of essential importance to practical mechanics to establish 

 mathematically the relations between a moving or living force 

 and a pressure or weight at rest, sometimes called a dead force. 

 As for example, it is frequently important to know the greatest 

 weight which may be placed on the head of a pile without caus- 

 ing it to sink deeper, the circumstances attending the driving 

 being known. It is chiefly to facilitate the solution of problems 

 of this nature that the following remarks are submitted. 



Among the mathematical works consulted on the subject, there 

 are several that allude to it under the title of vis viva, stating its 

 force to be proportional to matter multiplied by the square of its 

 velocity ; but there was found no expression for the exact meas- 

 ure of effect. 



A few quotations showing how the subject is sometimes treat- 

 ed, may not be out of place here. 



"Mathematically speaking, there is no comparison between 

 an active force and a dead one ; however, repeated experience 



