From: "JACK L. URETSKY (C) 1996; HEP DIV., ARGONNE NATIONAL LAB, ARGONNE, IL 60439" <JLU@hep.anl.gov>
Date: Thu, 10 Oct 1996 12:47:06 -0500 (CDT)
This is stricltly from memory, so I'll not get into detail.
A major 19th century industry was electroplating. If you know
some chemistry and valence stuff, you can relate the amount of material
deposited to the amount of charge carried. This led to an early definition
of the coulomb, and an accurate (pre-Millikan) estimate of the charge
on the electron. Old chemistry books (or encyclopedias) can give you
more detail.
Regards,
Jack