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LORD KELVIN, DR. M. MACLEAN, AND MR. A. GALT, ON THE 



68. TJie Diselectrifying Power of Various Filters was farther tested as follows : 

 Air, electrified in a metal vessel by a needle point kept electrified by a Voss 

 electric machine, was drawn through 340 centims. of block-tin pipe (0'91 centim. 

 bore), to one or other of the experimental filters which was connected to sheath 

 (fig. 8). After passing through A, the air was drawn through an insulated testing 

 filter, B, connected to the insulated terminal of the electrometer. B was a standard 

 filter of block-tin pipe, 5 centims. long, 0'66 centim. bore, and filled with fine brass 

 filings. Tests were occasionally made with A removed, to ascertain the diselectrifying 

 power of the standard filter (B) alone ; then A being inserted, the effect on B was 

 again noticed. 



69. The standard filter, B, was now removed, and the various tubes used in the 

 last experiments as tested filters (A's), were now tried separately as testing filters 

 (that is, insulated filters, B), connected to the insulated terminal of the electrometer. 

 The following are the particulars and deflections noted for 6 strokes of the pump in 

 1 minute : 



