Anthonie Heinsius wrote Letter L-160 to Leeuwenhoek about Robert Boyle's reaction to the letter about cochineal

August 3, 1685

This letter is known only by reference in another letter. The date is New Style, which was ten days ahead of the Old Style date of 24 July 1685 used by Heinsius in London, where he was negotiating the status of Bantam with the British for the Dutch stadthouder William III. See note 2 to Letter 105 [60] L-194 of 28 November 1687, Collected Letters, vol. 7, for more. By 1688, William would be king of England. He then appointed Heinsius grand pensionary (raadpensionaris) and delegated to him the governance of the Dutch Republic for the rest of his life.

In this letter, Anthonie Heinsius writes from London that Robert Boyle would like Leeuwenhoek to examine cochineal, among other things.

Heinsius initiated this sequence of letters in July by passing along to Leeuwenhoek a request from Robert Boyle that Leeuwenhoek examine cochineal. Leeuwenhoek did so and reported his observations in early August, after which Heinsius showed the letter to Boyle. In late August, Heinsius reported back on Boyle's response in Letter L-163 of 31 August 1685.

Heinsius’s previous letter to L. was Letter L-139 of 8 October 1683, to which Leeuwenhoek promply replied with L-141 of 14 October 1683. In his reply to the present letter, Letter L-162 of 10 August 1685, Leeuwenhoek reported on his investigation of cochineal, as Robert Boyle requested. However, Leeuwenhoek was on the wrong track because he thought that cochineal, a red dye made from insects, came from the seed of a plant. Heinsius’s next letter to Leeuwenhoek was Letter L-163 of 31 August 1685. The busy statesman Heinsius would not write another letter to his old friend L. until Letter L-515 of 28 February 1715, three decades later.


Letter L-194 of 28 November 1687 to the Royal Society

Mr. Anthonie Heinsius, LL. D., pensionary and counsellor of this city, one-time envoy extraordinary to His Royal Majesty of France, and then commissioner of this country to the court of His Royal Majesty of Great Britain, wrote to me from Westminster on 24th July/3rd August, 1685 that the Right Honourable Robert Boyle would be pleased if I examined, among other things, the cochineal.

I thereupon replied to the abovementioned Mr. Heinsius, on the 10th of August.