Rev. W. Whewell on the principles of Df/namics^ 4*c. 27 



toes nearly equal, but the right only two. The toes are said to 

 be connected by a membrane, a kind of periosteum insulating 

 the metacarpal bones and toes, and even passing beyond them 

 about six lines. Now M. St-Hilaire imagines that this mem- 

 brane extended to the envelopes of the placenta, but this is 

 merely a conjecture, and one founded on a hypothesis. 



It is not improbable that the description of the foetus in 

 question may ultimately form the subject of a distinct memoir ; 

 and should this happen we shall not fail to give it an early 

 place in this Journal. R. K. 



Art. V. — On the principles of Dynamics^ particularly as 

 stated by French Writers. By the Rev. W. Whewell, 

 M. A. Trinity College, Cambridge. Communicated by the 

 Author. 



During the course of the last century, a question was started, 

 and repeatedly discussed among mathematicians, " whether 

 the principles of Mechanics were necessary or contingent 

 truths ?" that is, whether the science could be established upon 

 axioms, drawn from the nature of things, and the relations of 

 our ideas, or whether it was indispensable for the proof of its 

 doctrines to recur to experiment and observation ? It might, 

 perhaps, have been expected that such a question would have 

 been easily decided, and that for its solution it would only 

 have been requisite to inspect any scientific treatise on mecha- 

 nics which pretended to strict logic in the deduction of its 

 fundamental propositions ; and where, of course, these prin- 

 ciples would be proved in the simplest manner which was pos- 

 sible. If, however, we examine the works of authors of the 

 most undoubted science and ingenuity up to the most modern 

 times, we shall find differences of principle among them which 

 seem to show that this discussion has not even yet led to any 

 opinion which possesses elementary clearness, and has found 

 universal reception. 



With respect, indeed, to the question above referred to, of 

 the necessary or contingent nature of the proof on which these 

 doctrines must rest, it seems now to be allpwed by the general 



