I remember reading a great answer [1] from Stack Exchange, that claims:

> the 1873 treatise used a pre-Heavisde form of vector calculus cannnibalized from Hamilton's quaternions ... only sparingly, to present the equations in capsule summary form.

Thanks for the reply. From your link, I now understand what does "vector calculus cannnibalized from Hamilton's quaternions ... only sparingly" means.

[1] https://hsm.stackexchange.com/a/15618