meter (with the extra resistance removed) and “A” is a direct current 
magneto generator having permanent magnet fields. 
The equation of the condenser is Q=EC; where Q is the quantity of 
electricity in Coulombs (ampere seconds), E is the voltage impressed, and 
C is the capacity in farads of the condenser. Studying this equation we 
find that if E is increased uniformly the quantity of charge Q on the con- 
denser plates will also increase uniformly. Since Q is increasing uni- 
formly with respect to time, the inflow of current is at a constant rate, 
ee fe OY 
1e,1—a- 
Likewise a constantly decreasing FE will give uw constant 
outflow of current. However, as soon as I reaches a fixed value all cur- 
rent flow in the circuit ceases since it is one property of the electric con- 
denser to arrest the flow of direct current. (The terms “inflow” and 
“outflow” refer tc those condenser plates that are directly connected to 
the instrument terminal. Of course as much current flows on to one set 
of plates as flows off of the other plates, the current in the line having a 
definite direction during an increase of voltage and the opposite direction 
during a decrease of voltage.) The magnitude of these currents are shown 
by the direct current instrument which consists merely of a coil swinging 
in a uniform magnetic field. Se long then as the voltage is changing uni- 
formly the instrument will read a constant value returning to zero oniy 
when FE ceases changing. It follows that if E does not change uniformly 
the instrument will not read a constant value but that its indications 
will be proportional to the instantaneous rate of change of the voltage. 
The direct current magneto is so designed that its voltage 1s directly pro- 
portional to its speed, so that changes of voltage at its terminals can only 
occur as a result of changes in speed. Therefore the instrument reads 
the rate of change of speed, i. e. acceleration whether positive or negative. 
In a preceding paragraph it was implied that an electric condenser 
allows no current to pass when the voltage E has reached a fixed value. 
This would be a fact if an ideal condenser could be made, but it is a well 
known fact that there is always some leakage even in the best condensers. 
This means tbat the dielectric has a definite value of resistance which 
varies with different conditions and substances, and according to Ohm’s 
4 
law the leakage current will be 1 — R This state of affairs renders our 
ideal circuit incorrect for any speed above zero because the instrument 
gets a small current in a definite direction that is practically proportional] 
