ON THE ELECTRICAL PROPERTIES OF PURE SULPHUR. 
97 
of adjustment. The improvements which can still be made are (l) greater strength 
in the support of the controlling system ; (2) increased fineness of adjustment of the 
controlling system ; (3) better arrangements for twisting the suspended fibre when 
the controlling system is mounted ; (4) increased uniformity of residual field ; (5) more 
perfect magnetic screening ; (6) numbering the divisions of the millimetre scale ; 
(?) observing in some place not affected by traffic along streets or roads. Of these, 
(5) and (7) are much the most important. 
Perhaps we ought to add that we are quite aware that at least as high a degree of 
sensitiveness as we have attained, may be got out of a much less elaborate instrument 
—on occasion. We have obtained such results ourselves with the “ old ” galvanometer. 
The point we wish to make is not that the sensitiveness is extraordinary, but that, 
such as it is, it is daily and hourly available with all the ease and certainty of observa¬ 
tion generally associated with instruments of, say, a thousand times less sensitiveness. 
Section V. 
Account of Experiments on Sulphur in Chronological Order. 
The first experiments were made with the arrangement of plates figured in the 
‘ Philosophical Magazine ' [5J, vol. 28, Plate 14, and the diagram of connections was 
the same as is given in the same volume, p. 470. The plates were of brass truly 
faced by scraping to a surface plate : they were first platinated by Roseleur’s method, 
and afterwards gilt and burnished many times. The object of the continual gilding 
and burnishing was to make the gold film as solid as possible ; for it was found 
that if the film was at all spongy, the sulphur penetrated it at a high temperature 
and acted on the brass below. There were also some few spots that seemed disinclined 
JL 
to gild. These spots were finally drilled out and plugs of gold were inserted by a 
dentist’s apparatus. The result was never perfectly satisfactory. The flatness of the 
plates, however, was preserved to such a degree that the mere contact of the upper 
clean plate was strong enough to lift the lower one, which weighed about 2 - 75 kilograms. 
These plates were prepared by Mr. Pollock. A film of sulphur was got between 
the plates by placing the lower one in the gold dish, and pouring in sufficient melted 
sulphur to cover it to a depth of about half a centimetre. The sulphur used was in 
this—as in every subsequent experiment unless the contrary be specifically stated—the 
sulphur recovered by the Chance process, distilled three times in hard-glass retorts. 
A. subsequent examination of the film showed that it was almost entirely monoclinic 
containing less than 1 per cent, of insoluble sulphur. The screws used for separating 
the plates had undergone a slight modification, so that the effective area as deduced 
from-a series of measurements by a fine pair of vernier callipers-was 193‘3 
sq. centims. From this it was estimated that the actual area was 190‘3 sq. centims; 
—3 sq. centims. being taken up by bubbles, and by a corner of the film which was 
MDCCCXCVI. — A. 
O 
