Hadley, John (1682-1744)
270; English mathematician who invented the reflecting telescope and the reflecting (Hadley's) quadrant.
282; The Wall, located in Britain, was built by order of the Emperor Hadrian, probably given during his visit to Britain in AD 122. Hadrian wanted to mark the northern boundary of his Empire. Expansion further north came later when from AD 140 to 163 Hadrian's Wall was briefly replaced by the Antonine Wall. The frontier soon moved south again, back to Hadrian's Wall. Interestingly, there is little evidence of major conflict on Hadrian's Wall. ; Wikipedia entry
17; a ditch with a wall on its inner side below ground level, forming a boundary to a garden or park without interrupting the view from within, being visible only from a close proximity (OED, 18th Ed.)
Haimo of Halberstadt
722; author of Rural Architecture in the Chinese Taste
554; transports M&D back to England; 704
131; English astronomer & mathematician; in 1676 he went to St. Helena to make the first catalogue of the stars in the southern hemisphere; he was the first to recommend observing the Transit of Venus to determine the sun's parallax; he predicted the return of the comet that was thereafter named for him; 152; 187; 438; 631
738; where Dixon stayed on his way to the Hollow Earth; a small town (pop. 9,561 in 1995) in Finnmark co., No. Norway, on Kvaløy island. It is the northernmost town of Europe, but its harbor is always ice-free. Tourists are attracted by its uninterrupted daylight from May 17 to July 29. There are fish-processing plants. Chartered c.1795, Hammerfest was heavily damaged by British naval bombardment in 1809, by fire in 1890, and by retreating German forces in 1944. 
Handel, George Friederic (1685-1759)
229; German-English composer of great reknown
365; a sword worn at the side; especially, in the 18th century, a short, curved sword. This is what Dimdown uses to attack Armand Allegre; 381; 386
Harland, Mr. & Mrs. John
330; M&D set up their observatory on his farm; 393; 441
310; river crossing ferry at the site of present-day Harrisburg, capital of Pennsylvania and not too many miles (c. 50 miles?) north of the M-D line on the Susquehanna River
658; Philadelphia land speculator at the M-D Line
201; English horologist who invented a timekeeper (chronometer) capable of compensating for errors due to variations of climate, thus solving the problem of determining longitude at sea and finally claiming the huge prize offered by the government; 213; 322; 436; 728
27; British admiral in command of the fleet blockading the French naval station of Brest in 1759. The French fleet was badly needed to assist the French army in Canada and in 1759, the French admiral Count de Conflans made a run at breaking the blockade. However, Hawke's fleet caught up to them and drove them into Quiberon Bay where nine French ships were destroyed, virtually incapacitating the fleet. This was key in Britains taking Canada from the French; 52Head of Elk
397; refers to the head of Maryland's Elk River. It flows through Cecil County and into Chesapeake Bay in the NE corner of Maryland just west of the Delaware border. Head of Elk was of strategic significance in the Revolutionary War: MORE
"Hearts of Oak"
Helen of Troy
634; See Finnbogi
549; reddish-purple colour
Henry, Patrick (1736-99)
395; American statesman & lawyer born in Hanover county, Virginia; 488
Henry VIII (1491-1547)
392; king of England from1509, and quite rotund
378; "hepato" = relating to the liver; "-machy" = dispute, controversy; the ancients considered the liver the seat of love; thus "Hepatomachy" might very well be "romantic intrigues"
249; "labor like"
352; Queen of Scotland
152; German: "Masters"
58; This might be an erratum. The Dutch spelling at the time was Heeren, spelled nowadays Heren, and always pronounced with a long e. The spelling used here is German. These 17 gentlemen formed together the representants of the shareholders of the VOC.
Herschel, Sir William (1738-1822)
213; British astronomer who, in 1781, discovered Uranus; 708
96; Hesperos was the god of the Evening Star (the Planet Venus). He was depicted as a white-winged god crowned with a starry oreole - a male version of Astraia. In vase-paintings usually only his face was shown shining in the heavens 
199; Charles Mason's sister, married to Elroy; 762
200; aka Aunt Hester; 763
623; The Xia Dynasty, established by Yu, ran from ca. 2205-1766 BC. This is said to be the empire that introduced slavery to China. The emperor was Chung K'ang, said to have ruled from 2159-2147 BC.
309; aka Ireland
450; on M-D Line kitchen crew; 460; veteran of Braddock's defeat, 614
The boatswain (pronounced "bo's'n") on the Seahorse, the frigate that takes Mason and Dixon to Cape of Good Hope. His name is a pun on the "Higgs boson" subatomic particle, aka "the God Particle", the existence of which was confirmed on July 10, 2012.
44; 68; 75; 349-51; 530; 565; 579; Bad, 615; 629; 708; 747
215; goblin; 505
297; working on Obs in Philadelphia
Hogarthian Society, Gin's
247; English satirical painter and caricaturist, William Hogarth (1697-1764) painted "modern moral subjects," including Gin Lane, a series of cartoons depicting the appalling levels of alcoholism and public drunkenness that resulted from the development of gin as the first drinkable distilled liquor that the urban poor could afford to abuse. The term "Hogarthian" often refers more to scenes of squalor and depravity than to Hogarth himself.
"A complete, largely unsens'd World, held within our own [...] waiting for some Summons to Light" 548; Dixon and Stig, 602-603; "the ancient City he has discover'd beneath the Earth" 707; Dixon taken by Being with "Very large eyes" 739; Plenty more at Wikipedia...; More info...
570; Maryland's Stamp Distributor
196; river in East Bengal, on which Calcutta (as in "Black Hole of") is located
764; "Fine with me, as Howard says to Howard, only please try not to kick that Switch to the main Battery, lest Mr. Dixon, -- oh dear. -- Ingvarr. What did I just say?" - a reference to the Three Stooges: Larry Fine, Moe Howard & Curly Howard [Thanks to Joe Gioia]
562; a seat or covered pavilion on the back of an elephant; 572
Hsi and Ho
622-28; The earliest recorded solar eclipse was 22 October 2134 BC. Ancient Chinese records note that "the Sun and Moon did not meet harmoniously." The two Chinese royal astronomers, Hsi and Ho, failed to predict it and were executed by the unhappy emperor; Court Astronomers for one of the Hia Emperors of China, 622-28; The Historickal Personages
623; "or Moon-station of Fang"; The Hsiu are twelve constellations analogous to western zodiacal signs, used to identify position around the Celestial Equator (as the zodiac locates it on the ecliptic). These twelve are also related to the twelve branches in Feng Shui. Fang is the constellation known as Ti-Chieh (Earth's Triumph) and is located within the 72 stars of evil influence. "Fang is a narrow hsiu, only covering a few degrees. Thus, solar eclipses . . . occurring in Fang . . . are moderately rare" (Newton 64)
626; "Here we must answer to the Market"; Here are three possible etymologies:
- Huang-En or Huang-Fan: Gods of their respective stars.
- Huang-Chin Li-Shih: Generic name for the Liu-ting spirits . . . Gold is the elemental force of the West, hence these genii are called the "Athletes of the Western Country," or Region of Gold.
- Huang K'un: The God of incense makers and sellers. In the time of Yu,
lightening having struck one of the trees in Hsi T'ien, the Western Paradise, one of the branches fell into the Blue River. When cast on the bank, it gave forth so sweet a perfume that it was taken and presented to the Emperor. No one but Huang K'un was able to explain its origin. Yu had incense-sticks made from it and ordered them to be burnt in honor of the Gods. From that time Huang K'un was regarded as the first promoter of this nation-wide industry.Hu Gadarn
228; O.E.D.: fr hum + strum, a roughly made or out of tune musical instrument; a hurdy gurdy
239; Thomas Hunter's third wife who married Ralph Dixon (George Dixon's father) after Thos Hunter died
239; Thomas Hunter's brother
229; Jeremiah Dixon's mother; 238; from a Newcastle family, 239
239; Mary Hunter's father
43; Jeremiah Dixon's maternal branch of the family, Quakers all
413; aka "Hurricane" (a large private party - 18th cent.); at Castle Lepton; 527
215; town about 3.5 miles south of Darlington and one mile east of Croft Bridge in Durham County, England
128; of St. Helena
7; eventual husband of Catherine Wheat; 575; Historical Sources
575; Tom's father
630: Oxford English Dictionary: "A phenomenon observed in some physical systems, by which changes in a property (e.g. magnetization, or length) lag behind changes in an agent on which they depend (e.g. magnetizing force, or stress), so that the value of the former at any moment depends on the manner of the previous variation of the latter (e.g. whether it was increasing or decreasing in value)"; MORE