Elected a member by the Royal Society

The election took place on January 29 (O.S.) / February 8 (N.S.)

When the meeting began,

The minutes of the 22d instant were read; and upon discoursing about the small creatures discovered by Mr. LEEWENHOECK in ginger-water mixed with pepper water, it was ordered, that some should be prepared against the next meeting.

The second order of business was the election of new members. The notice of it in Birch's History, vol. IV, p. 6, was perfunctory.

Dr. Heusch, Mr. Firmin and Mr. Houghton were elected; as was also Mr. Leeuwenhoeck upon the motion of Dr. Croune, and Dr. Gale was desired to draw up a diploma to be sent to him.

Note that Leeuwenhoek was not elected a Fellow of the Royal Society. Fellows had to sign the membership book and pay weekly dues whether or not they went to meetings. Leeuwenhoek was a foreign member, and he never attended a meeting or paid dues. The Society sent him free copies of all numbers of Philosophical Transactions, not just those in which his letters appeared.

Heniger's 1979 article (Dutch with some Latin) about Leeuwenhoek's diploma notes the by-law for fellows, dating from May 13, 1663 (O.S.), recorded in Birch's History vol. 1 p. 237:

We, whose names are under-written, do consent and agree, that we will meet together weekly (if not hindered by necessary occasions) to consult and debate concerning the promoting of experimental learning: and that each of us will allow one shilling weekly towards the defraying of occasional charges: provided, that if any one, ot more of us, shall think fit at any time to withdraw, he or they shall, after notice thereof given to the company at a meeting, be freed from this obligation for the future.

What about foreign members?

The first of them was Christiaan Huygens in 1663, when he happened to be living in London and could sign the book himself. The second, the German astronomer Johannes Hevelius (1611-1687), could not leave Danzig, where he was consul.

A year later at the meeting on April 13, 1664 (O.S.), Birch recorded (vol. 1 p. 410) the members discussed the by-law for foreign members:

When any person residing in foreign parts shall be elected into the society in due and accustomed form and manner, the said person shall be registered among the fellows of the society, and be reputed a fellow thereof, without subscription or admission in the usual form: any thing contained in the statutes, requiring subscription and admission, to the contrary nothwithstanding. And the said person may have an instrument under the seal of the society, testifying him to be elected and reputed a fellow of the society accordingly.

The requirement to attend a meeting, sign the members' Charter Book, and begin paying the weekly dues was waived for foreign members. Instead, they would receive an "instrument under the seal of the Society". That instrument was the diploma; Hevelius' was written on parchment and sent to him under a letter by Henry Oldenburg on May 11, 1664.

That degree of detail is available only until 1687, when Birch's History stopped. Up to that time, 36 foreigners were elected to membership in the Royal Society. Of them, 14 signed the Charter Book in London. That left 22 to receive diplomas. However, Birch noted only five. There is no other source that would indicate more than five. None of the originals has survived but four were copied into the Society's records and are reproduced by Birch. Heniger notes that the wording of the four surviving is very similar.

• Johannes Hevelius, 1664, for mathematics (especially astronomy), literature and philosophy
• Adrien Auzout, French astronomer, 1666
• Antonio Alvarez da Cunha, Portuguese man of letters, 1668, for mathematics, literature and philosophy
• Marcello Malpighi, Italian naturalist, 1669, for medicine, anatomy and philosophy.
• Leeuwenhoek, 1680, for several very ingenious experiments in optics

Explaining why these five foreign members and not the 17 others, Heniger argues that only those five were deemed by the Society's members to have shown a "singular respect for the society", a phrase from the record of Malpighi's election in Birch's History (vol II p. 352).