Short answers, pulled from the story.
The solar eclipse of the 29th of May 1919 was a total solar eclipse with a magnitude of 1.0719 that swept across South America and Africa. It is historically significant because it provided the first observational proof of Einstein's general theory of relativity, confirming that the Sun's gravity bends starlight by the amount Einstein had predicted.
Two expeditions were organized under the direction of Sir Dyson. Sir Arthur Eddington led one team to the island of Príncipe off the west coast of Africa, while Andrew Claude de la Cherois Crommelin and Charles Rundle Davidson led a second team to Sobral in Brazil.
Both expeditions observed the Hyades, a star cluster in the constellation Taurus. The apparent positions of these stars, as photographed during totality when the Sun's glare was blocked, were compared to their known true positions to measure the gravitational bending of their light by the Sun.
The maximum duration of totality was 6 minutes 50.75 seconds, making it the longest solar eclipse since the 27th of May 1416. A longer total solar eclipse would later occur on the 8th of June 1937.
A thunderstorm struck on the morning of the eclipse, and skies had been overcast for many of the preceding days. The clouds did not begin to dissipate until thirty minutes before totality, and astronomers were forced to take their photographs through gaps in the clouds during the eclipse itself.
Two eclipses in 1912 fell short. The 17th of April 1912 eclipse, nicknamed the Titanic Eclipse because it occurred two days after the ship sank, was hampered by superstition, underfunding, and insufficient totality. The 10th of October 1912 eclipse could not be photographed due to rain. The 8th of June 1918 eclipse also failed to produce usable results.