ON THE ELECTRICAL PROPERTIES OP PURE SULPHUR, 
88 
drawing (Plate 1). It might possibly be worth while to use fine silver wire, and would 
certainly be advantageous to have the wire specially lightly insulated, but we are 
too far from manufacturing countries to be able to take advantage of such expedients. 
The wire employed by us has a diameter of '05 millim. It was frequently necessary 
to make joints, owing to irregularities in the insulation. The best material for 
reinsulating the joints is a film of collodion, as it takes up less room than anything 
else we know of. 
(2.) The magnetic moment of each member of the suspended system should be a 
maximum. This again is not purely a matter of design. 
Our magnets were hardened circular discs stamped out of thin sheet steel. Each 
magnet consisted of two discs, one on each side of the support. Their dimensions 
were : 
Diameter.‘876 centim. 
Weight.'0309 gram each. 
Thickness.'008 centim. 
So that the weight of the suspended part is made up thus : 
gram. 
8 discs weigh .... 
. . . '2470 
1 mirror weighs .... 
Wire and cement . 
. . . '0660 
Total weight . 
'3615 
So that the weight of the mirror is only about one-eighth of the whole weight, and 
the magnets form about five-sevenths of the whole weight. 
At first we tried mica as a supporting material, but found it very much inferior to 
flattened aluminium wire, which can be twisted. A strip of mica, moreover, makes 
the combination more dead-beat; which, with our method of observation, is equiva¬ 
lent to a reduction of sensitiveness. 
We also rolled some sheet steel, '004 centim. thick, into small cylinders as 
described by Professor Langley, and compared the intensity of magnetization 
obtained with that of the small discs. The result is given in the accompanying 
table ; it will be noted the advantage is on the side of the disc. The experiments 
were made by Mr. Pollock. We dare say that better steel can be got ; but, unless 
Mr. Ellery, F.P.S. (of Melbourne), had kindly come to our assistance, we should 
have had none at all. 
