Hi Gary--
I enjoyed your essay very much. Hypothesizing how Newton could have used quaternions to get to Special Relativity is fantastic. Confession: I'm a huge fan of Newton and, in particular, have enjoyed reading about the development of Calculus (starting, of course, with the Newton-Leibniz blowup).
I do not claim to be an expert regarding quaternions. So, I was hoping that you might be kind enough to take some extra time to explain how your Eq. 10 would have helped Newton "lay the groundwork for Special Relativity". A few more words might be helpful for those of us who don't have the math at our fingertips. I know how in these essays, with the space and word constraints, it is tough to put in all of the extra explanatory asides and so forth.
I think that your essay has been undervalued by the community.
Best regards,
Bill.