the zero meridian of the Royal Greenwich Observatory

Greenwich Meridian 1 Greenwich Meridian 2 Greenwich Meridian 3 Greenwich Meridian 4Airy Functions
[Abramowitz & Stegun, section 10.4]

differential equation w"(z)=zw(z)

Ai(z)=c1f(z)-c2g(z), Bi(z)=(c1f(z)+c2g(z)),
c1 = 3-2/3(2/3), c2 = 3-1/3(1/3),
f(z) = (1/3)kz3k/(3k)! ,
g(z) = (2/3)kz3k+1/(3k+1)!
NIST Digital Library of Mathematical Functions



the previous zero meridian of the Orchilla Lighthouse on the isle of El Hierro

Get a free dictionary, e.g. Latin, from Freelang



page with two stamps celebrating suplementary 18th century measurings of a meridian length
Bill Thayer's superb site contains a fine online edition of the Historia Naturalis of Pliny the elder. Book 6, Ch. 37, 202-205 is the first historic reference to the Canary Islands, copied below in small print, to give you a taste (and desire for more), with the names of the individual islands in color.

202   Sunt qui ultra eas Fortunatas putent esse quasdamque alias, quo in numero idem Sebosus etiam spatia conplexus Iunoniam abesse a Gadibus DCCL p. tradit, ab ea tantundem ad occasum versus Pluvialiam Caprariamque; in Pluvialia non esse aquam nisi ex imbri. ab iis CCL Fortunatas contra laevam Mauretaniae in VIII horam solis; vocari Invallem a convexitate et Planasiam a specie, Invallis circuitu CCC p.; arborum ibi proceritatem ad CXL pedes adulescere.
203   Iuba de Fortunatis ita inquisivit: sub meridiem quoque positas esse prope occasum, a Purpurariis DCXXV p., sic ut CCL supra occasum navigetur, dein per CCCLXXV ortus petatur. primam vocari Ombrion, nullis aedificiorum vestigiis; habere in montibus stagnum, arbores similes ferulae, ex quibus aqua exprimatur, e nigris amara, ex candidioribus potui iucunda.
204   alteram insulam Iunoniam appellari; in ea aediculam esse tantum lapide exstructam. ab ea in vicino eodem nomine minorem, deinde Caprariam, lacertis grandibus refertam. in conspectu earum esse Ninguariam, quae hoc nomen acceperit a perpetua nive, nebulosam.
205   proximam ei Canariam vocari a multitudine canum ingentis magnitudinis — ex quibus perducti sunt Iubae duo —; apparere ibi vestigia aedificiorum. cum omnes autem copia pomorum et avium omnis generis abundent, hanc et palmetis caryotas ferentibus ac nuce pinea abundare; esse copiam et mellis, papyrum quoque et siluros in amnibus gigni. infestari eas belvis, quae expellantur adsidue, putrescentibus.

["Ombrios" is El Hierro or, possibly, La Palma. Notice the reference to the water providing trees]




an excellent walking guide is the Rother Wanderführer El Hierro (in German)