April 19

When the Diet of Speyer reimposed the Edict of Worms, six princes and fourteen imperial cities lodged a formal protest that in matters of conscience a majority could not bind them. From it their side took the name Protestants.

A convex lens of crown glass cemented to a concave one of flint brings red and blue light to nearly the same focus. Chester Moor Hall had done it quietly around 1730; John Dollond patented it, his son enforced it in court, and short, sharp refractors became possible. England had changed calendars…

At dawn about 70 militiamen under Captain John Parker faced the regulars’ advance guard. Nobody knows who fired first. Eight Americans were killed and ten wounded; one British soldier was hurt.

Here once the embattled farmers stood, / And fired the shot heard round the world. — Ralph Waldo Emerson, “Concord Hymn”, 1837 Here the militia fired back on orders, and the regulars retreated. By Fischer’s count the day cost 49 Americans and 73 British soldiers killed on the road back to Boston.

Eight years from Lexington to the peace treaty. Howard Peckham counted 6,824 Americans killed in action; with disease and the prison ships added, estimates of all American military deaths run to about 25,000.

Ten years of taxes, boycotts, riots and repeals. Nobody set out to leave the empire; the colonists claimed the rights of Englishmen, and Parliament insisted it could legislate for them “in all cases whatsoever”.

Within days some 15,000 militia from across New England had penned the British army inside Boston.

Lincoln proclaimed a blockade of some 3,500 miles of Confederate coastline, with 42 ships in active service. Winfield Scott’s plan to squeeze the South by sea and river was mocked as the “Anaconda”; in outline, it was how the war was won.

Of heart disease, aged 73, with Emma beside him. She recorded him saying, the night before, “I am not the least afraid to die”. The family planned to bury him in Downe churchyard.

Crossing the street in the rain, he slipped under a heavy horse-drawn wagon, and a rear wheel crushed his skull. He was forty-six. For a year she kept a journal written to him: “Pierre, my Pierre”.

When the SS came to deport the last Jews of the ghetto, a few hundred young fighters under Mordecai Anielewicz, 24, fought back for four weeks against tanks and artillery: the largest Jewish uprising of the war. The SS commander Jürgen Stroop ended it by blowing up the Great Synagogue and…

In a four-page magazine article, Gordon Moore of Fairchild noted that the number of components on a chip had doubled every year and predicted it would go on doing so for a decade. He revised it to every two years in 1975, and the industry treated the prediction as a schedule for the next…

Fiat built the Soviet Union a copy of its own factory on the Volga, in a city renamed after the Italian Communist leader Palmiro Togliatti. Its VAZ-2101, a toughened Fiat 124 sold abroad as the Lada, put private cars within reach of Soviet families, after years on a waiting list.

Launched ten years after Gagarin. The first crew could not get in: Soyuz 10 reached it but could not latch on. The second, Soyuz 11, lived aboard for 23 days.

Twenty-year-old Nasir Jones described Queensbridge in ten tracks and under forty minutes, over beats by DJ Premier, Pete Rock, Large Professor, Q-Tip and L.E.S. The Source gave it five mics, its top rating; it is still the album many rappers name as the best of the form.

Thirty-nine pharmaceutical companies had sued to stop a 1997 law letting the government import or license cheaper medicines. Facing protests worldwide, they withdrew the case weeks after the hearing began in the Pretoria High Court.

Independent shops in the United States held a Saturday of in-store performances and limited pressings sold nowhere else. It spread worldwide and became one of the busiest days of the year for vinyl.

Perseverance’s 1.8 kg helicopter made the first powered flight on another planet, carrying a scrap of fabric from the Wright Flyer. Planned for five flights, it made 72.