I am preparing a presentation on the famous “oil drop” experiment, directed by Robert Millikan in 1909. Specifically, I need to identify the placement of the devices at the ports of the oil can.
Here is a picture of it. I have placed six labels on it for identification:
It is clear that the device at [A] is the eyepiece of the microscope where oil drops were observed. And [B] appears to be the oil atomizer.
The port at [C] looks to be the connector for electrodes which charged the plates, which provided the electric force opposite to that of gravity when acting on the oil drop.
I went to Millikan’s manuscript on the experiment (“On the Elementary Electrical Charge and the Avogadro Constant”, Phys. Rev., Vol II, Series II, p. 109-143). On page 123 of this paper, it states (if I understand correctly) that the observation port is offset 18 degrees from the X-ray port, in the same horizontal plane. I take this to mean that [D] is the port where the X-ray device was attached.
My questions are:
- If [D] really is the X-ray port, why is it so close to the observation port?
- What is the port at [E]?
- What is [F]?
- Where is the barometer connected? Figure 1 on page 122 of Millikan’s paper shows a barometer, but I don’t see one on the picture above.
- Where is the port for a light source? On the other side?
- Is there anything on the other side of the can that is important to the experiment, that I missed?
Many thanks in advance for your input.