220 NOTICES OF THE MEETINGS [June VI, 
be entirely unaffected magnetically, 7.e. it would be a matter of 
absolute indifference to the needle whether it were moving or still. 
Matters may be so arranged that the wire when still shall have the 
same diamagnetic force as the medium surrounding the magnet, and 
so in no way cause disturbance of the lines of force passing through 
both; and yet when the wire moves, a current of electricity shall be 
generated in it. The mere fact of motion cannot have produced 
this current : there must have been a state or condition around the 
magnet and sustained by it, withinthe range of which the wire was 
placed; and this state shews the physical constitution of the lines of 
magnetic force. 
What this state is or upon what it depends cannot as yet be 
declared. It may depend upon the ether, as a ray of light does, 
and an association has already been shewn between light and 
magnetism. It may depend upon a state of tension, or a state of 
vibration, or perhaps some other state analogous to the electric 
current, to which the magnetic forces are so intimately related. 
Whether it of necessity requires matter for its sustentation will 
depend upon what is understood by the term matter. If that is 
to be confined to ponderable or gravitating substances, then 
matter is not essential to the physical lines of magnetic force any 
more than to a ray of light or heat; but if in the assumption of 
an ether we admit it to be a species of matter, then the lines of 
force may depend upon some function of it. Experimentally mere 
space is magnetic; but then the idea of such mere space must 
include that of the ether, when one is talking on that belief; or 
if hereafter any other conception of the state or condition of 
space rise up, it must be admitted into the view of that, which 
just now in relation to experiment is called mere space. On the 
other hand it is, I think, an ascertained fact that ponderable matter is 
not essential to the existence of physical lines of magnetic force. 
[M. F.] 
In the Library were exhibited : — 
Specimen of Auriferous Quartz, Nevada County, California, pre- 
sented by F. Catherwood, Esq. 
Portrait of Mr. Faraday, by G. Richmond, Esq. ; and of Dr. Rox- 
burgh, by J. Z. Bell, Esq. 
Axe (Marked Stanislaus, 1661), and Ancient Mace. [Exhibited 
by H. W. Pickersgill, Esq., R.A.] 
«« Solitude,” designed by J. Lawlor, Esq. and executed by the Messrs. 
Minton, for the Art-Union of London. [Exhibited by T. S. 
Watson, Esq., M.R.I.] 
Specimens of Iron Ore from Northants and of Malachite, from 
Siberia ;— Black Marble Vases. [Exhibited by Mr. Tennant.] 
