614 
Proceedings of the Royal Society 
portable electrometer. This instrument I took with me, and the 
following are the results of the observations made with it. 
During the voyage a number of observations were made, but of 
these only two sets were of any special interest. The first of 
• these was made in the Suez Canal, on Dec. 22nd. At 8 a.m., at 
noon, and again at 8 p.m. the readings showed a negative electrifica- 
tion of from three to eight divisions on the scale, the weather 
being entered as “fine and bright” and the wind as “ S., very 
light,” “E. by S., light breeze,” and “E.S.E., light,” respectively ; 
while readings taken at 1.30 p.m. and 7.30 p.m. gave a positive 
electrification of eight divisions on each occasion. This has consider- 
able interest in connection with some observations made in Madras. 
The other set was made in the Eed Sea, during a rather violent 
squall. In this case the readings varied very rapidly, from strong 
negative to strong positive, the readings an hour and a half before 
having been + 18 divisions. The variations took place so rapidly 
that no quantitative observations could be made, and in a few 
minutes, when the squall had passed over, the readings were found 
to be much as before, viz. , + 17 divisions. 
In Madras, a series of observations were made, extending from 
17th Jan. to 4th March 1877. These were made at 8.30 a.m. 
and 6 p.m. and showed a wonderfully steady state of electrification, 
varying from a maximum of +53 to + 19, with an average of 3 + 3. 
The morning and evening readings usually agreed very closely. 
In every case the electrification was positive, and the weather 
was fine without any rain. 
During this time the electrometer had to be recharged every 
two or three days, an operation which, though very simple in 
this climate, is by no means so simple in a climate so moist as 
that of Madras. After a time, I found it impossible to continue 
the observations at all, and sent the instrument home, to see if it 
could be in any way modified so as to suit the climate. On its 
return after a long delay, I found it leaked as badly as before, 
and so rendered observations almost impossible. The reason is 
doubtless to be found in the circumstance, that the air of Madras 
is not only moist, but is also very full of small particles of salt, 
which are constantly being carried from the surf by the sea breeze. 
The glass of the jar soon gets coated with these particles, and no 
