Intelligence and Miscellaneous Articles. 237 
Specimens of molybdenum received from M. Debray are magnetic ; 
and as this property is also possessed by molybdic acid purified by 
several sublimations, it cannot be attributed to the presence of foreign 
matters. The molybdates of soda and ammonia are diamagnetic ; 
the magnetic rotatory power is positive, but weak. 
Lithium and glucinum are diamagnetic metals; the compounds 
. of these metals, received by the author from MM. Troost and Debray, 
were most evidently repelled by magnets.—Comptes Rendus, July 6, 
1857, p. 33. 
THE IMPROVED INDUCTION COIL. 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 
I had hoped that after the statement which I have been obliged to 
give, in the course of discussion, in the Mechanics’ Magazine, of 
the proceedings of Dr. Noad and Mr. Bentley, that the latter gen- 
tleman would hardly have ventured to repeat his erroneous state- 
ments in proof either of his priority or his originality. 
In his last communication he has prudently dropped the former 
question, but still endeavours to substantiate the latter by assertions 
which will be found to prove the reverse. Mr. Bentley states that 
his machine was not opened in my presence; but this is immaterial, 
I am content to take his own description of it; and when I explain 
the construction of mine, which was made twelve months before his 
was commenced, I think it will be seen that the two machines are 
perfectly identical. 
Ist. Mr. Bentley asserts, but I do not know upon what authority, 
except his peculiar propensity for guessing, that I wind my second- 
ary wire close to the cheeks of the gutta-percha bobbin; and that 
he tried this plan himself at first, but could not succeed, and then 
adopted the plan of winding each layer shorter than the preceding 
one, so as to gain insulating space over the ends. Mr. Bentley has 
misrepresented my mode of arrangement, for J do not wind my wire 
close to the cheeks of the gutta-percha bobbin, but allow as much 
of the insulating medium to project beyond the layers as is sufficient 
to prevent the passage of sparks between them. I suppose that Mr. 
Bentley mistook the material with which the outside of my coil is 
finished, for wire ; it is not wire, though it looks like it; and the 
cheeks of gutta-percha have nothing to do with the coil, but are 
merely put on for the sake of neatness. In this first point, then, the 
two machines are not dissimilar, but identical. 
2ndly. Mr. Bentley says that ‘‘his own coil differs from Mr. 
Hearder’s, and is formed of very fine parallel wires, each wire being 
magnetically and electrically insulated from the others;” but he does 
not say how mine is constructed, which I submit he ought to have 
done in order to prove the dissimilarity which he assumes. It hap- 
pens, however, and his friend Dr. Noad was perfectly aware of the 
fact, that my iron wire is also composed of fine parallel wires, elec- 
