164 ANNUAL OF SCIENTIFIC DISCOVERY. 



THE EFFECTS OF LIGHTNING ON WIRES. 



In a paper addressed to the Academy of Sciences by M. F. P. 

 Leronx, in which the author examines certain phenomena which 

 natural philosophers have either hesitated to explain, or have 

 confessed to belong to an unknown action of the electric fluid, 

 one of the most curious of these phenomena is that of the undula- 

 tions produced in the wires by the discharges, and the momentary 

 diminution of length they experience in consequence. This short- 

 ening in the wires has been observed by others, who admitted the 

 diminution of length, but failed to perceive the undulations. M. 

 Ed. Becquerel, however, instead of keeping the wire stretched 

 between the two poles, suspended it by one end, and simply 

 stretched it with a very light weight, and in this way he was en- 

 abled to ascertain the existence of very perceptible undulations. 

 M. Reis carried the matter farther, and concluded that the diminu- 

 tion of length was but a consequence of the undulations. M. 

 Becquerel found that under the influence of successive discharges 

 the undulations would not only continue, but increase ; at the 

 same time, however, there is no perceptible oscillation ; for, on 

 observing the wire attentively at the moment when it becomes 

 luminous enough under the influence of electricity to become 

 visible, its shape appears distinctly defined. What is the cause 

 of the undulatory deformation it undergoes? Our author at first 

 suspected it to be owing to some action of terrestrial magnetism, 

 and he therefore subjected the wire to the influence of powerful 

 magnets, but without success. He then operated on wires left 

 entirely free at their nether extremit} 7 , and the undulations under 

 such circumstances became much stronger, two or three dis- 

 charges being sufficient to render them quite perceptible ; but 

 their order is so irregular, and they assume such a variety of 

 shapes, that no rule can be laid down regarding them. One 

 thing, however, did not escape the author's notice, namely, that 

 the temperature caused by the discharges was not without influ- 

 ence upon them ; for, in order to obtain deep undulations, it 

 must remain within certain limits, not below a dark-red heat, and 

 not so high as to soften the metal much. In the latter case the 

 undulations are exceedingly minute and close together; platinum 

 wires being then best suited for the experiment. Our author, 

 therefore, concludes that the phenomenon alluded to does not 

 require any new principle for its explanation, and is a simple 

 question of temperature. As the heat engendered by the dis- 

 charges increases, the wire tends to increase in length by dilation ; 

 but as this power of dilation acts also transversely, there is also a 

 tendency to increase in diameter, and it is to this double molecular 

 action the undulations must be ascribed. 



NEW FORMS OF THE HYDRAULIC PRESS. 



At a meeting of the 'Massachusetts Institute of Technology, 

 Prof. Rogers spoke of some novel forms of the hydraulic press, as 

 exhibited at the Paris Exposition. In the old forms the intermit- 



