384 Miscellaneous Intelligence, 



In support of this principle are cited various well-known 

 effects, amongst which are, the penetration of an open door by 

 a candle shot from a gun, no motion being communicated to 

 the door ; the legerdemain trick of breaking a stick resting on 

 the edges of two glasses filled with water, by striking it sharply 

 in the middle with another stick, the glasses not being moved or 

 the water spilt ; the cutting off of twigs and flowers in a garden 

 or the fields, by a sharp blow on the stems with a light switch ; 

 the separation of a snake into portions when struck with a hazel- 

 tree rod ; the mode of blasting introduced by the engineer Jessop, 

 in which, after the introduction of the powder into the hole, the 

 upper part is filled merely by sand : in all these cases M. Allou 

 considers the effect as due to the want of reaction in the passive 

 body, as regards the attack made upon it by the active body. 

 " All bodies resist motion," says M. Francceur, in his Treatise on 

 Mechanics, " and it is in resisting that they receive it. Those 

 which are instantaneously pierced or destroyed, not having offered 

 appreciable resistance, should not therefore receive motion, and 

 this is confirmed by experiment. " Speaking of the branches, 

 flowers, and the snake, cut in pieces by the switch, " the shock 

 is so rapid and unexpected, that the muscular fibres of the reptile, 

 as well as those which form the tissue of the flowers and branches, 

 have not time to react. Now it is this want of reaction which 

 constitutes the phenomenon;" and in the experiment of Mr. 

 Barnes, " is it not natural to think that the shock on the steel by 

 the cutting edge of the disc is so sudden and unexpected, that the 

 molecules of the first have not time to react on those of the latter, 

 and are thus rapidly removed at each contact." 



Other facts of a similar nature with the former are then cited 

 in support of this view of the matter, but they add no new proof. 



The author thinks that the mechanical principle of which the 

 phenomena described are the effects, has not had sufficient impor- 

 tance attached to it. We may be permitted to observe that we 

 think if any thing else was intended in the explication than was 

 previously well known, it has been left in too obscure a state to 

 persuade us of its importance, or indeed of its accuracy, It seems 

 difficult to comprehend how, when two similar bodies meet, they 

 should possess different properties dependent merely upon the su- 

 perior velocity of one over that of the other ; and taking the cases 

 of the two ivory balls, we doubt whether any difference would be 

 observed in the effects occasioned by their coming together with a 

 certain great velocity, whether the one or the other ball had all the 

 velocity, or whether each had half. Again, if in all the cases quoted, 

 including the curious experiment of Mr. Barnes, of cutting steel 

 by iron, things could be changed, so that the body in the experi- 

 ment actually in motion could be at rest, and the body previously 

 at rest could have the motion transferred to it, would not the 



