0
On Hills and Dales, although published almost a century and a half ago in Philosophical Magazine is surprisingly (at least in my search engine bubble?) difficult to find in full text. Best I could do was p.233, paper XLIII in a collection of Maxwell's works.
Is there an anglophone equivalent of Gallica?
Edit: Cayley's 1859 On Contour and Slope Lines was, happily, more readily available.