p.1
Rongo-Rongo:
October 1842:
R.M. Ballantyne:
moai: Monolithic statues carved by the early inhabitants of Easter Island which overlook the Pacific Ocean.  Although the origin of the moai is obscure, some scholars believe that the statues bear similarities to sculptures found in the Andean highlands of South America.  These figures, which number about 600, are mostly between 3 and 6 m high; the largest is 11 m high.  Some weigh up to 45 metric tons.  During a time of internal conflict, it is thought, all of the statues were toppled from their bases. Examples of an ancient script exist but have not been deciphered.

p.3
Rapa Nui: Chilean dependency situated in the Pacific Ocean, about 3,700 km west of Chile.  Famous for the moai, the triangle-shaped island has an area of 117 sq km. Its Dutch discoverers called it Paaseiland (Easter Island) to commemorate the day it was sighted.  Its Polynesian name is Rapa Nui.

p.4
Anakena Bay:
Marco Polo: Ship named after the medieval Venetian explorer of China featured in 'Marco Polo'.

p.7
the lip of the island's volcanic crater: Easter Island consists of three extinct volcanoes (the highest reaches 538 m) and craters, separated by low plains.  The original Polynesian population used stone tools to carve huge statues of humans, apparently in quarries within the volcano of Rano Raruko or here Ranu Raraku, the Navel of the World.

p.12
obsidian:a volcanic glass, usually of rhyolitic composition, forms by rapid cooling of a viscous lava.  It is usually black in color but occasionally red or brown (if iron-oxide dust is present), clear, or green.  Obsidian displays a well-developed conchoidal fracture, which makes it an excellent material for arrowheads, knives, and other sharp tools and weapons. Archaeologists use obsidian tools to trace trade routes, because such tools are relatively rare and each occurrence has a slightly different chemical composition. Thus the source of primitive obsidian tools may be located even if the tools have been traded across thousands of kilometers.

p.14
The Pride of Hannay:

p.17
Daniel Defoe, Robinson Crusoe:Best known for the novel Robinson Crusoe (1719), Daniel Defoe (1660-1731) was an English writer of social criticism, satire, and novels.  Literary historians consider Robinson Crusoe the first successful English novel and Defoe as one of the originators of realistic fiction in the 18th century.  The Life and Strange Surprising Adventures of Robinson Crusoe of York, Mariner was suggested by the actual experiences of Alexander Selkirk, a marooned sailor.

p.19
Windjammer: (Text submitted by David Whittam) a sailing ship; also : one of its crew.
flying fish: Flying fish are surface-dwelling fishes of the open oceans and belong to the family Exocoetidae. They are easily recognized by their enlarged pectoral fins and the elongation of the lower portion of their tail fin, and by their characteristic leaps and glides over the ocean surface. One species, the Atlantic flying fish, Cypselurus heterurus, is found in warm waters on both sides of the Atlantic, and in the West Atlantic it is common in the Gulf Stream. It reaches 38 cm (15 in) in length. Flying fish do not fly by flapping their pectoral fins; instead, they leap into the air, hold the fins rigidly outspread, and glide like flying squirrels.
Jack Devitt:
ratlines, spanker: (Text submitted by David Whittam) Ratlines are any of the small transverse ropes attached to the shrouds of a ship so as to form the steps of a rope ladder.  The spanker is 1 : the fore-and-aft sail on the mast nearest the stern of a square-rigged ship.  2 : the sail on the sternmost mast in a schooner of four or more masts .
bowsprit: (Text submitted by David Whittam) a large spar projecting forward from the stem of a ship.
ten knots across the North Atlantic towards the Equator: The measurement of speed in knots is a nautical method.  A rope with knots tied in it at regular distances has a weight or buoy attached to one end, and the buoy is thrown over the side.  Knots in the rope are pulled into the sea at regular time intervals, and an estimate of speed can be made.  The rope is reeled back in.  Alternatively, the buoy can be thrown off the bow of the ship and the time it takes to pass the stern is measured, the length of the ship already being known.

p.22
nine-days:
fruit: By 1872 the nature of scurvy had been known for some time; Captain Cook had been one of the first navigators to come up with a remedy for it one hundred years before.  Cook carried sauerkraut, as well as  pease (a kind of soup or porridge with peas, I assume).  Both were rich in vitamin c and kept well over long periods of time.  How the Tweed's crew keeps fruit for weeks on end is unknown.

p.23
The Hunter's Promise:
gulls: The gulls hang about the ship waiting for food because they have nowhere else to go.  Having followed the Tweed too far out to sea, they can't go back.

p.24
"Reroute control from main to subsystem" et cetera: Leela comes from a space cargo culture; a stone-age civilisation arisen from the ruins of a spaceship crashed on a jungle planet.  Survivors broke into two factions, the Tesh (technicians) and the Sevateem (survey team).  See 'The Face of Evil'.

p.26
skipjack: (Text submitted by David Whittam) 1 : any of various fishes (as a ladyfish or bluefish) that jump above or are active at the surface of the water; especially : SKIPJACK TUNA  2 : a sailboat with vertical sides and a bottom similar to a flat V.
sauce tartare: Mayonnaise and relish.  Goes good on fish. 
webspinner:

p.27
horda: (Text submitted by David Whittam) Nasty vicious biting things from 'The Face of Evil'.

p.28
750:
the Evil One: (Text submitted by David Whittam) The role attributed to the Doctor in the Face of Evil.

p.30
the Hunter's Eye:
crossbow: If the Sevateem were a stone age civilisation, how did they get crossbows?
Janis thorn: improvised weapon from Leela's world.  It paralyses.   

p.31
The Times:
check sequence:

p.32
Kent:

p.33
French windows:

p.34
the British Museum:
the Portobello Road:

p.37
directionless winds: The Doldrum belt circles the Earth near the Equator.  The Doldrum belt is an interface between hemispheric atmosphere systems.  In the Northern hemisphere water tends to spin counter-clockwise down the toilet, and weather systems tend to break to the right.  In the Southern hemisphere water tends to spin clockwise and weather systems break to the left.  This is all an effect of the Earth being a spinning round body.  The Earth rotates from west to east, so any mass of air draw towards the equator from the North Pole by centripetal acceleration will lose ground and drift eastwards because the land under it rotates faster the farther it is from the pole.  Meanwhile, any air mass moving north from the equator gains ground and moves west as the Earth below it rotates slower.  Air breaking west from the equator meeting air breaking east from the Pole forms counterclockwise weather systems.  The opposite is true in the Southern hemisphere.  On the equator there is no impetus for air masses to spin in either direction, hence the lack of wind.  By the way, did you know that the Moon appears upside-down in the Southern hemisphere?
singing: Crossing the Equator is one of those nautical occasions for good-natured hazing.  There's a big party and anyone who's never gone south of the equator (in the purely literal sense) gets painted blue or some such mild punishment.
'Octopus's Garden': Beatles song from the Abbey Road album, written and sung by Ringo Starr.