Pelorus Sound is typical of New Zealand coastal locations, i.e. there is a semi-diurnal tide modulated on a spring-neap cycle, generated by the superposition of M2 (lunar, semi-diurnal) and S2 (solar, semi-diurnal) tidal constituents. Other tidal constituents, notably N2 (semi-diurnal, generated by the ellipticity of the moon’s orbit), introduce further modulation, meaning that the spring-neap cycle is not exactly repeated. The tidal range varies between at neap and at spring. (These values are calculated from a sea level time series, July 1997 – February 1998, at Pelorus Sound entrance.) The propagation of this tidal signal into Pelorus Sound has not been well
The Sea and Little Fishes Granny is the sea, and the other witches are the fishes (at one point Nanny says that calling Granny 'full of pride' is like calling the sea 'full of water'; water is what the sea "is"). It is based on the "ancient phrase" "The big sea does not care which way the little fishes swim", which Pratchett made up at some point before the story, and finally used in "Night Watch". The witches appear as supporting characters in the Tiffany Aching stories starting with "The Wee Free Men". "A Hat Full of Sky" further develops the Witch Trials and the