Konstantin LeBlanc Cordas returns to bedevil Indy in this book. He was previously the leader of the Group of Six in The Sky Pirates. It is revealed here that Cordas and Halvar Griffin, who also appeared in The Sky Pirates are the same man.

Treadwell asks Gale why the map was kept in the Glen for safekeeping when it could have been stored in the vaults of the Bank of London. There was no Bank of London as such at this time. He is probably referring to the Bank of England, the central bank of the United Kingdom, established in 1694 (the Bank of England is mentioned specifically in another context on page 141).

Chapter 8

Page 110 mentions "Glastonbury and the Tor". A tor is a rock outcrop on the top of a hill. The Tor of Glastonbury is said to be the burial place of King Arthur.

On pages 117-118, Indy demonstrates the form and working of a Möbius strip, to suggest what is happening on the old forest road they are currently on, which somehow keeps bringing them back to the same spot, like a loop. A Möbius strip is a surface with only one side. The image to the right from Wikipedia by David Benbennick is a Möbius strip made with a piece of paper, given a half-twist and taped together at the ends. If its full length were crawled by an ant, the ant would return to its starting point having traversed both sides of the paper without ever crossing an edge.

Indy spots a barracuda tattoo on Tony's forearm and confronts him about it, knowing that this same tattoo was seen on some of the attackers of St. Brendan's Glen. Tony explains that it is not Ton Ton, but there is a group composed of Haitians, Jamaicans, and others from the Caribbean Islands, whom he says are mercenaries, wearing the picuda tattoo. It's hard to confirm exactly what he is referring to when he says "Ton Ton". There was a brutal Haitian secret police called Tonton Macoute, but it was not created (by dictator François "Papa Doc" Duvalier) until 1959. Tonton Macoute (Uncle Gunnysack) is also a Haitian folktale character who is said to capture unruly children in a gunnysack and takes them away to eat for breakfast. Picuda is a species of barracuda, Sphyraena picuda.

On page 124, Indy and the other guests of St. Brendan Glen spy a unicorn's head mounted along with those of many other animals in the great hall. Indy had brushes with the reality of unicorns in The Unicorn's Legacy and The Interior World.

On page 129, Caitlin remarks on her people's trust of Indy, due to his experience in dealing with many cultures, his travels, his sense of kinship, etc. She also comments on his having seen the Dance of the Giants. This occurred at Stonehenge in, of course, Dance of the Giants.

Chapter 9

On page 135, Pencroft snarks that Treadwell's story of an unmarked map leading to a horde of gold sounds like blindman's buff or pin the tail on the donkey. "Blindman's buff" and "pin the tail on the donkey" are both children's games in which a child is blindfolded and expected to perform a task (tag a nearby person or pin a paper tail on a cut-out of a donkey).

Di Palma reveals that his fellow Italian agent Dr. Filipo Castilano (seen in The Sky Pirates) is in the hospital, probably for the next year, undergoing skin grafts and other medical treatments after being almost killed in an explosion as the result of events at the end of The Sky Pirates.

Di Palma is said to be a member of the secret Six Hundred of the Vatican. Castilano was also said to be a member of this group in The Sky Pirates. The secret Six Hundred of the Vatican appears to be fictitious.

On page 140, Pencroft mentions the Museum Council of Great Britain. This appears to be a fictitious council.

Pencroft's remarks about the effects of the American Civil War on Great Britain in 1863 at the bottom of page 141 and top of page 142 is roughly accurate. The part about the transfer of gold between the Confederacy and England and the deal for England to help protect Confederate ports with its navy is largely fictitious.

Chapter 10

Indy, Gale, and Treadwell have dinner at Treadwell's favorite pub, the Hogsbreath Inn in London. This appears to be a fictitious establishment.

Treadwell mentions Sir Galahad and Morgan the Fay on page 155. These are both personages from the Arthurian legends, Galahad the illegitimate son of Sir Lancelot and Morgan the Fay ("fay" being a mystical entity) usually depicted as Arthur's villainous or morally ambiguous sister.

    Gale asks Indy how it is he knows quite a bit about radios and batteries and electrical stuff. Indy remarks that he learned a lot from someone named Jack Silverstein, an inventor and research scientist. As far as I can find, this is a fictitious researcher/inventor. Indy also remarks that when people ask about the history of electrical power, names like Edison and Tesla come up and mentions it's only been thirty years since Edison produced a worthwhile light bulb. Thomas Edison (1847-1931) and Nikola Tesla (1856-1943) were famed scientists/inventors, largely in experimenting with electricity and the invention of electrical devices.

    Indy's statement about a worthwhile Edison light bulb only thirty years ago is rather spacious. Edison announced his first "working" light bulb in 1879, with a filament that lasted about 14.5 hours, but soon had one that could last over 1200 hours. He kept improving on that over the next couple of decades. Indy may be talking about the brighter-burning tungsten filament bulbs introduced in 1904 by European inventors Sándor Just and Franjo Hanaman.

On page 158, Indy tells Gale about someone named Wilhelm Kroner who discovered what looked like ancient parts of a dry cell battery in Parthinian ruins of about 226 BCE and when the parts were put together, they generated an electrical current. As far as I can find, Kroner is fictitious. It may be that author Caidin has obfuscated the truth slightly since it has not been proven and does not conform to the timeline of this novel, and may be referring to the Parthian (not Parthinian) battery (commonly called the Baghdad Battery) discovered by Austrian archaeologist Wilhelm König in 1936.

Another mention of Indy's, Thales of Miletus, was an Ancient Greek philosopher who is known to have studied the workings of static electricity around the 6-7th century BCE.

Chapter 11

MI5 learns that Cordas and a small group appear to be headed for Hamburg, Germany.

On page 167, Indy has pieced together that Cordas is heading to the United States after he boards the Graf Zeppelin in Friedrichshafen, Germany. The Graf Zeppelin was a German transatlantic passenger airship offering service from 1928-1937. LZ 127 was the construction number of the vessel when it was built by the Zeppelin Transport Company (Deutsche Zeppelin-Reederei) in 1928, as Indy says.

Chapter 12

Indy, Gale, and Treadwell cross the English Channel to Cherbourg on a ferry. From there, they'll drive to Paris, then take a train to Friedrichshafen. The English Channel is the narrow stretch of ocean that separates England from the European mainland. Cherbourg is now Cherbourg-en-Cotentin on the Cotentin Peninsula of France on the English Channel. Since they are arriving in Cherbourg, it is likely they left from Bournemouth in county Dorset, England.

On page 172, the cab driver tells Gale, "Merci," for the drink from her flask. Merci is French for "thank you."

Page 173 reveals that Gale went to school in Middlesex. Middlesex is a county in England.

For the trip from Paris to Cherbourg, Indy goes by the alias Henry Parker. The false identity papers provided for Indy by MI5 for the alias suggests that he is a zookeeper at the London Zoo who went to university in San Diego, California and formerly worked in the cattle country of Texas.

During the trip, Indy carries a Schmeiser (sic) pistol given to him by Treadwell as a backup to his Webley. "Schmeisser" refers to

Hugo Schmeisser (1884-1953), a German developer of pistols and machine guns, many of which bear his name (and even some he didn't).

Blau fuel mentioned by Pennington at the end of the chapter as the engine fuel used by the Graf Zeppelin is an artificial gas similar to propane, rarely used in modern times. It is named for its inventor, German chemist Hermann Blau (1871-1944). Blau fuel was actually used by the Graf Zeppelin because it weighs only slightly more than an equal amount of air, so the zeppelin would not lose buoyancy as it burned fuel.

Chapter 13

Zeppelin passengers and crew are described as having to wear specially-designed, soft footwear to avoid static electricity in the hydrogen-buoyant air vessel. I have been unable to confirm if this was actually a requirement when travelling in zeppelins at the time.

On page 179, Kasner says ja and kapitan. These are German for "yes" and "captain".

Kasner tells Gale the engines on the Graf Zeppelin are Maybachs. Maybach is a German luxury car brand.

Indy sees on the zeppelin's flight chart they'll be flying over Jan Mayen Island. Jan Mayen is a volcanic island of the Arctic Ocean with no permanent population. It is officially a part of Norway.

Chapter 14

Indy mentions Captain Eckener, commander of the Graf Zeppelin. Hugo Eckener (1868-1954), manager of Luftschiffbau Zeppelin, was the real world captain of the vessel.

When Indy tells Gale he has been talking to the zeppelin's navigation officer, he tells her the man's name is Karl Jaeger. But whenever his first name is mentioned in the rest of the book, he is Kurt Jaeger. I guess Indy simply forgot the correct name for a moment!

On page 191, Jaeger says "Wunderbar!" This is German for "Wonderful!"

Chapter 15

As the chapter opens, the zeppelin is flying over the Denmark Strait. The Denmark Strait is a strait between Greenland and Iceland connecting the Arctic Ocean to the Atlantic Ocean.

On page 197, Indy reminisces on an old Ford he used to drive as a youth on an old country road. This may have been during his time living with his father in Utah.

Chapter 16

The message Indy receives aboard the zeppelin from Treadwell is code-marked as being from Sherwood, which Indy interprets as Sherwood Forest. Sherwood Forest is a royal forest in central England, famed as the home of the legendary Robin Hood.

As Indy states on page 202, "Johnny Reb" was a common nickname in the north for the Confederate soldiers of the south during the American Civil War of 1861-1865.

On pages 202-203, Kingsley Plantation, Little Talbot Island, and the St. John's River are all actual places in northern Florida.

On page 203, Port Jacksonville is the sea port of Jacksonville, Florida. Indy speculates the Civil War gold arrived at the port from England, then was delivered to Steinhatchee on Dead Man's Bay where it would have been loaded on Confederate ships and taken to New Orleans. These are all actual locations in Florida, though "Dead Man's Bay" is actually called Deadman Bay.

Also on page 203, Gale and Indy reference a song about an old gray mare. This is "The Old Gray Mare", an American children's folk song from the 1800s, including the lyrics referred to here, "The old gray mare, she ain't what she used to be."

On page 204, Indy explains the "Seminole" reference in Treadwell's coded message. Obviously, the Seminoles are a real world Native American tribe and the story of the Unconquered People is quite fascinating on its own if you get a chance to read about them. The tribe exists as both Oklahoma and Florida Seminoles, they never surrendered to the U.S. government during the Indian Wars, and they counted among their members African-Americans who escaped slavery in the south.

Chapter 17

Page 211 reveals that Indy is skilled in the combat sport of fencing.

Chapter 18

On page 228, Jaeger tells Indy the zeppelin will be landing in about 36 hours at Lakehurst. This is a town in the U.S. state of New Jersey.

When Indy does a bad impression of what he thinks Merlin would have said in regards to their new friend Jaeger, Gale tells him its terrible and that Merlin would flip-flop in his grave if he could hear him. Indy then responds, "With all due respect, I believe he can." Indy is likely thinking of the discourses he's had in visions of Merlin in some previous adventures, specifically, Dance of the Giants and The Seven Veils.

Chapter 19

As this chapter opens, the Graf Zeppelin is flying over New York City, Manhattan, and the Hudson River as it heads into New Jersey.

On page 234, the Volga River is an actual river in Russia.

Page 238 reveals that Indy is a close friend of the curator of the American Museum of Natural History on the west side of Central Park in mid-Manhattan.

On page 239, Indy is given a shiny, new Webley .455 caliber (to keep) by U.S. agents.

The agents also give Indy a half dozen flash grenades. Indy remarks he had used them before in the African Congo, describing an encounter with a nasty leopard. This seems to be an unrecorded incident. Possibly, it occurred during his time as a soldier in the Belgian Army when he was stationed in the Congo for a while ("Trek of Doom" and "Oganga, the Giver and Taker of Life").

On page 241, Indy compliments Caitlin that she's like an Annie Oakley with a bow. Oakley (1860-1926) was an American sharpshooter.

Chapter 20

No notes.

Chapter 21

Indy and his entourage take off on the next leg of their chase in a Sikorsky S-38 amphibian with Wasp engines from Floyd Bennet Field on Long Island Sound. The plane is marked as Pan American Airways. Wasp was a series of engines models made from the 1930-50s by Pratt & Whitney. Pan American Airways was an American airline from 1927-1991. (Photo from Wikipedia.)

On page 254, Indy tells Gale and Caitlin to memorize the details of his maps and charts, particularly those of the town of Olustee Station and the battle site of Ocean Pond, near White Springs. These are all actual locations in the state of Florida.

Also on page 254, Indy mentions the American Civil War battles of Gettysburg and Antietam. These were actual historical battles fought in 1863 and 1862, respectively.

On page 255, Indy says he has seen and fully believes in the use of divining rods.

The Battle of Ocean Pond/Olustee Station described by Indy on pages 256-260 seems to be accurate to history, as far as it goes.

On page 262, Indy informs Carruthers that he believes in a psychic effect left behind on old battlefields where hundreds of people died in agony. This does make some sense for him, as he has encountered spirits of the dead in past adventures, notably The Pirates' Loot, Tomb of Terror, and The Ghostly Riders.

Chapter 22

On page 269, Maclenny is an actual town in Florida.

Chapter 23

On page 281, Indy tells Caitlin that Cordas' men have Enfield .303s, which he is familiar with from the war. This is an actual rifle used by the forces of the British Empire during the first half of the 20th Century.

Chapter 24

No notes.

Chapter 25

Indy explains to his crew that the "cavalry" that had just ridden through the pine barrens was an historical reenactment of the battle of Olustee Station that takes place every year on the anniversary of the battle. Indy says this is the 66th anniversary. There is such an annual reenactment by costumed cavalry players, though I've been unable to confirm if it was taking place as long ago as 1930 (in fact, online research from battleofolustee.org suggests the very first reenactment took place in 1964). Indy seems to characterize "Olustee Station" and "Ocean Pond" as two separate battles, but research seems to indicate they are two names for the same battle, fought on February 20, 1864. So the current date at this point in the novel must be February 20, 1930.

Chapter 26

On page 312, Indy tells Caitlin they could not have accomplished what they did without the influence of Pencroft and the help he got them from Whitehall and the American Secret Service. Whitehall is a road in Westminster, central London, where the seat of the UK government is located.

Page 315 reveals that Pencroft was also the former "oracle" of St. Brendan's Glen.

On page 316, Indy remarks that Di Palma, in his glittering uniform, looks like a doorman at the Waldorf-Astoria. This a reference to the original Waldorf Hotel in New York City, known for its luxurious accommodations and uniformed employees.

On page 316, Di Palma remarks that he is of the ancient and venerable Di Palma family which helped bring Italy into the world. Although it may be that his boast is an exaggeration, "Di Palma" is the name of an ancient and noble family of southern Italy (where he had previously said he was from) that has historically held many political and ecclesiastical stations in the country.

At the end of the novel, Pencroft, in his role as the head of the University of London, tells Indy he has taken the liberty of arranging for him (Indy) to investigate some new archaeological intrigue that has been brought to his attention. It is never revealed what this was. After this novel, Indy is never seen working for the University of London again. In the next story in the chronology, "The Viking Scroll", set in December 1930, Indy is working for the (American) National Museum; whether he is also teaching somewhere at that point is not revealed.