They're linear. Surely energy moving in the landscape would move in swirly patterns around the contours of the hills and the geology? More like water. I don't think Chinese feng shui practitioners have detected any ley lines, though they're very good at finding energy movements in the landscape. There are also electrical currents in the Earth's crust and mantle, which interact in a complex way; these are known as telluric currents. Ley lines are also not the same as song-lines, which are actually known to Indigenous Australians as the 'Footprints of the Ancestors' or the 'Way of the Law'.
When Alfred Watkins talked about leys, he was talking about prehistoric trackways. The whole concept has been expanded to mean mythical energy lines across the landscape, such as the Mary and Michael Line (which is sometimes depicted as swirly, but does arbitrarily join up unconnected monuments).
Also, ley lines are becoming congested:
Ley lines in certain parts of Britain are becoming so congested with hippies, travellers and mildly frightening-looking people with coat hangers that the government has today announced a multi-million pound ten year ley line building programme.I'm not saying that there isn't energy in the land (it feels to me as though there is); I'm just deeply skeptical about it moving along mysterious and arbitrary lines.
Of course, if you want to argue for ley-lines as a mythopoeic or metaphorical construct, that would be different. But I very much doubt that they objectively exist, especially as there are no ethnographic parallels and little or no evidence for them in indigenous British folklore.