TO THE MOTION OF MACHINES. 531. 



advanced and receded by the arrangements above mentioned respec- 

 tively to 30'' and 40". We see that in this case tlic needle is rather 

 less affected than in the case of the disjunction of the second wire ; but 

 I expected, as a necessary consequence, that the needle would not be 

 at all aifected, for I had received no shock nor spark in the analo- 

 gous experiment. I confess that at present I am unable to enter into 

 an explanation of the striking difference which subsists between the 

 current of reaction and the magneto-electric current. 



23. 



With regard to the magnetic machine, it will be of great importance 

 to weaken the effect of the counter-current, without at the same time 

 weakening the magnetism of the bars. It is the alternate combination 

 of the pairs of plates or the voltaic pile which permits us to increase 

 the speed of rotation at will. We know that the magnetic power of 

 tlie current is not sensibly augmented by increasing the number of the 

 pairs of plates, but the counter-current is considerably weakened by 

 it, being forced to pass through a great many layers of liquid. In 

 fact, on using twelve voltaic pairs, each half a square foot, instead 

 of four copper troughs, each with a surface of two square feet, 

 which I had hitlierto used, the speed of rotation rose to at least 250 

 — 300 revolutions in a minute, a number which I was able only to 

 estimate, having been unable to count them. The acid which I em- 

 ployed was extremely weak, and had served for many previous experi- 

 ments. The development of gas was imperceptible either by sight or 

 smell. Having immersed two thick copper wires in the cups p and o, 

 and having taken hold of them with my hands dipped in salt watei", I 

 received during the motion of the apparatus violent shocks, and felt 

 an extreme pricking sensation in the upper part of my body. The 

 mechanical effect of the apparatus corresponding to the speed of 250 

 to 300 revolutions in a minute has been valued at half the force of a 

 man. I shall at a future time apply to it an exact dynamometric 

 apparatus. 



I have not been able to make further experiments on this subject, 

 and I am obliged to interrupt my investigations for a time ; but from 

 what precedes, I may perhaps be justified in maintaining, that the su- 

 periority of this new motor, with regard to the absence of danger, the 

 simplicity of the application, and the expense of the materials necessary 

 to keep it in action, is placed beyond doubt. 



Vol. I.— Part IV. 2o 



