Folks: I'm reading the Oxford Dictionary of Weights, Measures and Units (Oxford University Press, 2002), and just encountered something that is flabbergasting to me.
Apparently prior to 1960, the letter D was an accepted symbol for deka/deca. In 1960 the symbol was changed to what we know today, da. In other words, prior to 1960 the symbol for decagram was Dg,for decameter was Dm, for decajouloe was DJ, etc. Now they are dag, dam, and daJ. What in the world possessed the SI committee (CGPM) to change this? D was far more consistent with the rest of the symbols for prefixes than da -- prefixes >1 are mostly capital letters, da is the ONLY prefix symbol that is not one letter. Surely there was some justification for this . . . anyone know what it was? Jim
