66 THE ANTARCTIC MANUAL. 
VIIL. 
ATMOSPHERIC ELECTRICITY: 
INSTRUCTIONS FOR THE OBSERVATION OF ATMOSPHERIC 
ELECTRICITY. 
By Lorp Ketviy, G.C.V.O. D.C.L. LL.D. F.R.S. 
THE instrument to be used is the portable electrometer described 
in Sir Wm. Thomson’s reprint of ‘Papers on Electrostatics and 
Magnetism,’ Sections 368-378.* Full directions for keeping the 
instrument in order, preparing it for use, and using it to make observa- 
tions of atmospheric electricity, are to be found in Sections 372-376 ; 
these are summarised in the following short practical rules: 
I. The instrument having been received from the maker with 
the inner surface of the glass, and all the metallic surfaces within 
clean and free from dust or fibres, and the pumice dry ; to prepare 
it for use: 
(1) Remove from the top the cover carrying the pumice. Drop 
upon the pumice a small quantity of the prepared sulphuric acid 
supplied with the instrument, distributing it as well as may be over 
the whole surface of the stone. There ought not to be so much acid 
as to show almost any visible appearance of moisture when once it 
has soaked into the pumice. Replace the cover without delay, and 
screw it firmly in its proper position, and then leave the instrument 
for half an hour or an hour, or any longer time that may be con- 
venient, to allow the inner surface of the glass to be well dried through 
the drying effect of the acidulated pumice on the air within. 
(2) Turn the micrometer screw till the reading is 2000. (There 
are 100 divisions on the circle which turns with the screw on the top 
outside, and the numbers on the vertical scale inside show full turns 
of the screw. Thus each division on the vertical scale inside corre- 
sponds to 100 divisions on the circle; and 20 on the vertical scale is 
read “2000.") Introduce the charging rod and give a charge of 
* A copy of this book has been sent by the Author for the use of the officer or 
officers to whom the observations of atmospheric electricity are committed. 
