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Another scale found in NMR spectroscopy literature from the 1960s and 1970's is the tau (τ)-scale, where τ = 10 ppm − δ. This scale had numeric values increasing from left-to-right across the spectrum, so was no longer "backwards." The (τ)-scale has been abandoned and, like the antiquated "upfield" and "downfield" designations, should be avoided in the modern era of FT NMR.
Reich HJ. Structure determination using spectroscopic methods. Syllabus for Course 605. University of Wisconsin, Madison, 2014. (See Section 5.02 for discussion of the "backwards" δ scale). Excellent on-line resource for structural NMR, available at this link.
What is meant by a chemical shift?