i 879 *] Proceedings of Societies . 449 
hand, repelled from the plate. The neutral line is also altered. 
In the first case it shrinks in size, in the second it expands. 
A small thick disk is wholly magnetised lamellarly ; a disk en- 
tirely magnetised radially becomes slightly conical in shape. In 
the acftual telephone the disk is flat at the middle and conical 
at the edges. As the neutral ring shifts, the diaphragm will 
assume new nodal lines. Dr. Thompson concludes that the 
molecular theory is not, therefore, necessary to account for the 
speech of the telephone, although it may assist. As confirming 
this view, he found that with iron rings round a cardboard dia- 
phragm and an iron centre-piece the enunciation was good, 
though the timbre was altered ; whereas with radial pieces of iron 
on the cardboard the timbre was good, but the enunciation bad. 
Dr. Thompson next wrote on a saw blade with a magnet, and 
dusted iron filings on it, which arranged themselves so as to 
trace the writing. This is usually shown on a steel plate, but a 
saw retains the virtue for six or eight months. A modification 
of this experiment due to himself consisted in writing on the 
blade with one pole of a powerful battery, the other pole being 
connected to the end of the blade. 
The third “ note ” recommended the use of fine steel fibres, 
got by breaking iron gauze of thirty-two meshes to the inch, 
instead of iron filings for exhibiting magnetic lines. The fourth 
note showed that the lines of force got by filings fixed on cards 
are magnetic, that of a magnet acfting as a magnet. The fifth 
note explained that solid magnetic “ figures ” could be got by 
coating iron filings in shellac to make them light, and floating 
them in water, or by mixing filings in a soft paste of plaster-of- 
paris, which could be cut into sections on hardening. 
May 10. — Mr. Wollaston explained the construction of Gower’s 
improved form of Bell’s speaking telephone. The older form, 
made of wood or ebonite, is open to the objection that it has a 
very weak voice, soon gets out of adjustment from changes of 
temperature, and requires a twisted hand wire, which is liable to 
break. Gower’s form has a comparatively loud utterance, is 
constant, and does not require to be held in the hand, but may 
be laid on a table or hung on a wall, a speaking-tube leading 
from it to the operator’s ear or mouth. The “ call for attracting 
attention is also within the Gower telephone itself ; whereas in 
the hand telephone it is an auxiliary apparatus. Every organ of 
the old telephone has been modified to form the Gower. The 
magnet in the Gower is of a horse-shoe form, very powerful, the 
two poles being brought very] close together, and each pole is 
mounted with a small coil of fine wire. The diaphragm is much 
thicker and larger than the Bell diaphragm. The case is of 
brass, to expand equably, and a speaking-tube is fitted to the 
front of the diaphragm. The call consists of a musical reed 
attached to the diaphragm, so as to be opposite a small slit in 
