192 Mr. Herschel on certain motions produced in 
NOTE. 
51. Since writing the above, Mr. Faraday has been so good 
as to show me a Paper, published by M. Serrulas, in the 
Journal de Physique for 1821 (vol. 93,) in which are related 
one or two of the appearances described in this Lecture, and 
other very curious ones referable to the same causes (though 
not apparently regarded by him as being so.) As the phe- 
nomena themselves are interesting, and the theory of them 
adopted by him is (as I shall easily show] insufficient, I shall 
be pardoned for extracting the whole passage from his 
Memoir ; regretting at the same time not having been able 
to find a former Paper on the subject, mentioned by him, in 
which his explanation is given at full length. 
52. The phenomena in question relate to the singular gyra- 
tory motions assumed by alloys of potassium wffien floated 
in small fragments on mercury under water. After noticing 
those of the alloy of bismuth, which he describes as particu- 
larly forcible and lasting, he goes on to say, 
53. “ Ne seroit-il pas interessant d’etudier Paction electrique 
qui se manifeste dans cette circonstance pendant Foxidation 
du potassium P’-—' “ Elle me semble digne d’attention pour sa 
liaison avec la decomposition de Peau dont elle depend uni- 
quement. * * * * 
54. “ La pellicule legere qui se forme dans ce cas n’est que 
le bismuth divise provenant de Palliage retenant entre ses 
molecules des bulles d’hydrogene extremement fines. Cette 
pellicule, comme je Pai dit, est attirde avec une grand promp- 
titude par les substances metalliques mises en contact avec le 
