1876/] The Newly-Discovered Force. 189 
are small wires the force will not pass — any long interval, at 
least — in sufficient quantity to produce a spark on the other 
side. 
Secondly . The Extra Current under Ordinary Conditions of a 
Circuit. — It has been suggested that the force might be the 
extra induced current ; but that current, as is well known, 
obeys all the laws of the other forms of induced electricity, 
produces decided chemical and physiological effects, causes 
a deflection in the needle of the galvanometer, everywhere 
gives constant evidence of polarity, and, so far as is known, 
cannot exist without a circuit. The spark of this force 
does not scintillate as much as the spark of the extra current. 
Nothing is easier than to prove the presence of the extra 
current ; whatever this force may be, it cannot be that cur- 
rent in ordinary circuit. 
Thirdly. Statical Electricity of High Tension. — High tension 
statical electricity, such as is obtained from statical ma- 
chines, gives a jumping spark ; its physiological effects are 
very powerful, and even dangerous ; it can charge bodies 
and things ; and when connected with the earth by a good 
earth-conneCtion it at once disappears. The spark of this 
force is scintillating, not jumping, requiring light contact to 
obtain it. Examined under the microscope, even, it does 
not appear to jump any more than the spark of dynamical 
electricity. Moreover, this force has no demonstrable 
physiological effects, cannot charge persons or things, and 
when connected with the earth or floor by the best possible 
connection it can still be drawn off from the conductor. 
Fourthly. Statical Electricity of Low Tension.— Low tension 
statical electricity obeys the laws of statical electricity of 
high tension in this respeCt — that it totally disappears when 
connected with the earth or with the walls of the room 
which are supposed to become polarised by it. Again, low 
tension statical electricity affeCts the electroscope and 
electrometer, and ought to charge the Leyden jar. Thom- 
son’s quadrant electrometer, which this force thus far has 
not affeCted, is a very delicate test for low tension statical 
electricity. 
Mr. Edison has found that low tension electricity, such as 
is obtained from the free poles of a single galvanic cell, 
does not behave at all after the manner of this force. 
When the tension is increased up to sixty-five cells, and is 
further increased by employing a condenser composed of 
numerous sheets of tin-foil separated by paper dipped in 
paraffin, and having a capacity of 34 microfarads, yet when 
connected with the earth the electricity at once and entirely 
