I am on my 4th year on Electrical Engineering education. Over the years the concept of earth in electric circuits bugged me. And now, again, I came across with something which I cannot understand.
Take a look at this ancient-patent. It belongs to Amos Emerson Dolbear, an eminent man of science: https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US350299.pdf
Here, between rows 14 and 19, he talks about "[...]a ground the potential of which is considerably above the normal[...]" and again he writes "[...]a ground the potential of which is considerably below the normal[...]".
i) What does he mean by "normal" potential?
ii) How can you make a buried terminal to have different potential than the ground? Terminal is buried, therefore terminal's potential has to equal be equal to the earth potential (which is accepted as zero potential, right? -Who accepts this? Why they accept this? Is there an evidence regarding the level of potential of the soil/earth?). The only sort-of-explanation I can come up with is that he does not reduce the ground resistance considerably. He keeps the resistance between the buried terminal and the earth, hence this allows two different potential levels on the different sides of the earth resistance.
iii) If we accept the icky-explanation above, how does a current flow into the earth? Is not earth, which contains sand, soil, rocks, minerals and mines, organic waste, an insulator? Certainly, it should not be a conductor.
I know I burst out the questions all over, but I am very ethusiastic to understand this. Thanks for your attention. -- imp0nderablef1uid
Edit: To make the question more clear, I summarize the question as follows:
i) how can you get different potential than earth potential on a terminal buried into the ground, and, ii) how can this work, i.e. how can currents flow into what seems like an awful conductor?