Intelligence and Miscellaneous Articles. 319 
It will be necessary, therefore, to have recourse to another hypo- 
thesis, and, I believe, to take into account the variable thickness of 
the liquid stratum or sheath which adheres to the solid body. This 
hypothesis has been suggested to me by a series of experiments 
which I have made upon the elevation of the solution of protochlo- 
ride of iron between two parallel iron plates which I fixed to the 
poles of a Ruhmkorff’s electro-magnet. The lower extremities of 
these plates were immersed in the solution, and the values / and b 
for the different distances 2¢ were already known. A current was 
then passed into the apparatus, of which the intensity was gradually 
increased and measured, when the magnetic liquid was seen to rise 
between the two planes, often to twice or three times its original 
height, whilst the surface acquired the curvature suitable to this new 
elevation ; but for each intensity of magnetization the volume raised 
remains evidently constant whatever be the distance of the two 
planes ; in one word, things go on as if the constant capillarity had 
been doubled or tripled. We know, however, from the experiments 
of Brunner and Mousson, that the attraction of the liquid upon itself 
is not altered by its magnetization; and, on the other hand, the 
minuteness of the changes of form which the liquid undergoes when 
the polar surfaces are not immersed in it, and the fact that the augmen- 
tation of the volume elevated is independent of the distance of the 
planes, prove that we have not to do with an effect of magnetic 
attraction exerted at a distance. I think, therefore, that these facts 
can only be explained by the increase of thickness of the adherent 
stratum, an increase which may be proved directly. 
It will be understood, also, that as every change of temperature 
may cause this thickness to vary, the influence of temperature may 
be very different from that foreseen by the theory, only taking into 
account the dilatation of the liquid. —Comptes Rendus, May 18, 1857, 
p. 1022. 
THE IMPROVED INDUCTION COIL; 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 
I am surprised to find that Mr. Hearder, after his communication 
to the Mechanics’ Magazine for July 11, has again accused me of 
having copied his induction coil. He there states, that at the con- 
clusion of one of his lectures at the London Institution, Mr. Shuter 
of Farringdon Street, when speaking about my induction coil, 
asserted “‘ that he (Mr. Shuter) had had almost as much to do with 
its construction as Mr. Bentley, since all the different plans for car- 
rying out the mode of insulation, &c. were concocted between them 
at his house; that Mr. Bentley had tried various thicknesses of 
gutta-percha with different degrees of success, and at length on one 
occasion came running to him (Mr. Shuter) with breathless delight, 
telling him that he had actually produced a spark nearly two inches 
in length. ‘These statements were made in the presence of my 
friend Dr. Letheby, and with such an air of honest frankness that | 
could not but credit them,” 
