200 Prof; Marianini's Examination of an Experiment 



VIII. We may conclude from what has been said, that the 

 fourth experiment of Professor Faraday, which, according to 

 Signor Fusinieri, is itself demonstrative of the truth of M. dela 

 Rive's theory, is at least inconclusive. 



And here it may be asked, whence then comes that alteia- 

 tion in the conductibility of the apparatus ? And M. de la 

 Rive will reply that the agitation of the liquid or the cleansing 

 of the plates increases the transmissibility for the electricity 

 of the same; and I shall add that the alteration in the relative 

 electromotive faculty, or, which is the same thing, in the elec- 

 trotism of the plates, also concurs in this. By the current, 

 indeed, the electrotism of those plates in which the electricity 

 enters, becomes positive, and those from which it proceeds to 

 pass into the liquid negative, and that alteration proceeds 

 from the matter which the current collects upon the plates 

 themselves. Now by the agitation of the liquid, and brushing 

 the plates gently with a feather, all or a part of this matter 

 which alters the electrotism of them, and hence necessarily 

 sti'engthens the voltaic current, is removed. I was convinced 

 that this was connected with the phaenomenon, by observing 

 that in the second experiment of the preceding paragraph, if 

 any one of the plates in which the electrotism becomes nega- 

 tive is brushed with a feather, there is an increase of the cur- 

 rent much greater than when one of those in which the elec- 

 trotism become positive is brushed; and we know that the 

 changes in electrotism to positive are, cccteris paribus, more 

 trifling than the changes to negative*. 



IX. The above remarks relative to the experiments in 

 question are those which are most obvious, and which suffice 

 to show the little or no importance which it has relatively to 

 the theory of the electromotors. It may, however, assist those 

 who desire to repeat that experiment and to study it, briefly 

 to bring under their notice some other phenomena which 

 may present themselves, and which do not escape the atten- 

 tive observer. 



Sometimes the feather is scarcely introduced into the liquid 

 when the force of the current is increased, and at other times 

 it is lowered. At times the said force decreases when the feather 

 is scarcely withdrawn from the liquid, at others it increases. 



In two' cases the force of the current is seen to increase at 

 the moment when the feather is introduced into the trough 

 or cup in which are plunged the plates of the voltaic pair. 



1st. When the vessel being small, the level of the liquid 

 increases by the immersion of the feather, and this is not in- 



* See the Memoir upon the alterations produced by the voltaic currents 

 in the electrotism of the principal metals, 1837, p. 140. 



