The resistance across the scope inputs is about 1M, the same as out circuits resistance causing the voltage drop across R to be about 1/2 the applied voltage. Change the calibration of Ch1 so that voltage is the same.
The time constant is much smaller as the gap in the capacitor is made wider.
All the components of the circuit can be seen here. The capacitor gap is small. A high dielectric constant material is made with water saturated sponges in a zip lock bag. This is then inserted into the capacitor.
The resistance is set on a decade resistance box to 1.1 Mega Ohm.
The function generator is set to a square wave of 797.3 Hz. The negative side of the function generator, Channel 1, Channel 2 and the capacitor are connected together.