TO THE MOVEMENT OF MACHINES. 19 



shaken by the fuUowing experiment. 1 had a steel cyHnder con- 

 structed, bored longitudinally in the direction of the axis ; it was 

 O^-IS in length, 6™-002 inner diameter, and 0'"-005 sohd thick- 

 ness. This cyhnder was suspended by several silk tlireads not 

 twisted. Its inherent magnetism was very weak, the duration of 

 an oscillation amounting to 103"'5. The inner surface was ex- 

 posed to two magnetic bars which were only 0'""004 in thickness, 

 and were made to slide Avith great caution in the direction of 

 the inner angles, as is usually done in magnetising by the 

 double touch. Four poles, placed symmetrically, having been 

 rubbed each ten times, the effect of these forty frictions was to 

 reduce the duration of an oscillation from 103"*5 to 31"'l. The 

 operation having been repeated, but with the other poles, 

 distanced from the first 45°, the duration of an oscillation was 

 reduced to 26"'95, and after a third repetition, to 25"*7. Re- 

 peated frictions had no more influence on the duration of the 

 oscillation, which might, however, still be reduced to 23""1, by 

 rubbing the outer surface in a similar way. This experiment 

 proves that, in fact, the inner sui'face is susceptible of being 

 rendered magnetic, but we must suppose that the separation of 

 the magnetic fluid takes place only in the rubbed portions, as is 

 the case in the experiments of M. Haldat. A magnetism dif- 

 fused uniformly over the entire surface cannot be admitted. 

 This experiment, simple though it be, it seems to me, may 

 nevertheless contribute to establish our notions as to the dis- 

 tribution of magnetism. 



As to the action of an electro-dynamic hehx placed in the in- 

 terior of a hollow steel cylinder, and traversed by magneto- 

 electric discharges, no variation in the magnetic condition was 

 perceptible. Care had been taken to isolate the helix as well as 

 possible, and to destroy in part the maenetism which the cylin- 

 der had acquired. The dm-ation of an oscillation amounted to 

 36", and this time did not vaiy even when a succession of dis- 

 charges in the same du'ection were maae o pass through the 

 helix. I was not able to tiy more energetic discharges : but the 

 development of the magnetism being subject to circumstances 

 which depend entirely on peculiar and accidental properties of 

 the steel, it cannot be exactly predicted whether electric currents 

 would or would not produce some effect of magnetization. 



B 2 



