16 
MR. E. RUTHERFORD OH A MAGHETIC DETECTOR OF 
energy in the conducting wires and spark gap is tabulated. The calculated value of 
the resistance of the wires of the discharge circuit was ’4 ohm, so that the remainder 
of the resistance is due to the great absorption of energy in the air break. 
The above curve represents the relation between the length of the S23ark and the 
apparent resistance that the spark offers to the discharge. The ohmic resistance of 
the air break is probably very variable, depending on the intensity of the charge at 
any instant, but the absorption of energy is quite definite and may be expressed in 
terms of the non-inductive resistance which, when placed in the circuit, would absorb 
the same amount of energy. 
It will be observed that the damping of the oscillations increases rapidly with the 
length of the spark, and that the resistance of the air break increases very rapidly 
with its length. 
It was also found that the damping depended on the capacity when the inductance 
and spark length were kept constant. The damping and also the resistance of the 
spark were found to increase with increase of capacity. For example with an air 
break of ’32 centim. the damping and resistance are given below. 
Capacity. 
Ratio of Oscillations. 
Resistance. 
JOOO 
•94 
2-2 
2000 
•9 
2-6 
4000 
•81 
3-8 
When the Qapacity of the circuit was small the damping was found to be very 
small. If iron wires were put into the place of the copper wires in the discharge 
circuit, the damping was found to be great for all capacities investigated. 
When the capacity of the circuit was only 130 electrostatic units, and inductance 
2400, no appreciable damping was found for an air break *5 centim. : When the 
copper wire was replaced by an iron one of the same dimensious, the second half¬ 
oscillation was only ’6 of the amplitude of the first. 
