ON THE ELECTRICAL PROPERTIES OF PURE SULPHUR. 
107 
Zero setting on bit of glass. 10 observations, ‘346773. 
Difference, ‘0095832 inch = ‘024341 centirn. thickness of film. 
The differences are probably clue to imperfect dusting of the bits of film. The film 
was very crumbly and the broken bits were strongly electrified and difficult to 
remove. This measurement of film thickness is the most unsatisfactory part of the 
work. In calculating specific resistance and specific inductive capacity, the ratio of 
thickness to area has to be known. 
The area has to be corrected for the effect of the edu-es. In the case of the 
O 
electrostatic measurement, i.e., the determination of the specific inductive capacity, a 
correction to the area can be calculated as already mentioned, and may be taken at 
-f- ‘26 centirn. In view of the specific resistance being dependent on so many 
different factors, it w r as not worth while to try to calculate a separate correction, so 
that the corrected area has been used both for the calculation of specific inductive 
capacity and specific resistance. 
This area is 156‘385 '26 or 156‘645 sq. centims. 
The ratio of corrected area to thickness is, therefore, 
156-645 
•024341 
6427‘4. 
The arrangement of apparatus adopted for making the measurement of the 
resistance of this film will be understood from the diagram. 
Two days experimenting were absorbed in curing leaks, contact effects, &c. 
galvanometer was simply used with a lamp and scale. 
Fi°-. l. 
The 
.5 
—-1 
r -©-— e - 1 
A B C D E F (fig. 1) is a reversing key, put to earth at E. 
H is a contact key. 
T, T are insulating supports of glass and ebonite. 
The terminals of the battery are reversed when necessary by interchanging the 
wires. 
A key, not shown, is provided for connecting A and F or C and D, so as to cut out 
the galvanometer. 
Before and after making an observation tbe wire is disconnected from the top 
plate at P, and hung on the support at T. Nothing touches the upper plate except 
the sulphur and connecting wire. Consequently, if no deflexion occurs when the 
wire is disconnected from P and hung on T, even when the reversing key is put over, 
it shows that the insulation is sufficient. 
p 2 
