ISO Prof. Marcet on the Action of 



Whence we obtain — 



Distance of the 



position of rest from 



100. 



Divisions 

 of scale. 



millims. 



Observed repulsion. 



Divisions of 



scale. 



B. 



niLLlims, 

 A. 



Distance of the pole Time of 

 of the magnet from vibra- 

 the central point of 

 action in the ball. 



millims. _ , 



Seconds, 



tion. 



Repulsive force, 

 milligrammes. 



Observed. Calculated. 



27-3771 



66-7417 



49-8833 



41-53125 



36-26875 



31978 

 7-7959 

 5 8267 

 4-8511 

 4 '2364 







39-5646 



22-5062 



1415415 



8-89165 





 4-5981 

 2-6289 

 1-6533 

 1-0386 



x^ 7-7959 

 •^+15-8267 

 .:r-|-24-85U 

 .r+34-2364 



349-46 

 301-59 

 323-75 

 336-56 

 342-44 





 005246 

 002603 

 0-01515 

 000919 





 0-05246 

 002719 

 001494 

 000899 



The three last values of the last columns are calculated from 

 the second, upon the assumption that x — 25 millims., and that 

 the action is inversely as the third power ot'lhe distance. With 

 this assumption we again constantly arrive nearly at the surface 

 of the ball of bismuth. 



Although the calculated values agree sufficiently with ob- 

 servation, I by no means regard the experiments sufficient to 

 deduce from them the two following positions, that — 



I. The repulsive action acts principally upon the nearest 

 surface of the diamagnetic body. 



II. That this repulsion decreases as the third power of the 

 distance of the pole of the magnet increases. 



In the first place, the experiments are not sufficiently nu- 

 merous, and require to be repeated with modifications; and 

 secondly, it should be observed that the ball was contained in 

 a cylindrical wooden case, the inside and outside of which was 

 coated with tinfoil. Now if the cause of the repulsive action 

 is owing to an induction, perhaps, of electric currents which 

 the pole of the magnet excites in or upon the ball, it is highly 

 probable that it would excite similar induction upon the coat- 

 ing of tinfoil, or even upon the wood of the case, which 

 would react upon the ball and so complicate the total effect. 



XVII. On the Action of Chloroform ow the Sensitive Plant 

 (Mimosa pudica). By Professor Marcet of Geneva*. 



WHEN one or two drops of pure chloroform are placed 

 on the top of the common petiole of a leaf of the sen- 

 sitive plant, this petiole is seen almost immediately to droop, 

 and an instant after the folioles close successively pair by pair, 

 beginning with those which are situated at the extremity of 



* Read before the Societe de Physique et d'Histoire NatureUe, Oct. ] 9, 

 1848, and communicated by the Author. 



