Chronology of events:

For some events, the year is certain but the month and day are not. Example: We know only the year for the collections of Leeuwenhoek's letters published in Dutch during his lifetime.

For other events, the season or month are certain but the day is not. Example: Leeuwenhoek mentions that someone visited him "last month".

On the other hand, many events did indeed happen on the first day of a month. Example: public appointments to Delft's city offices took effect on January 1 of each year. Thus:

  • A date of January 1 in a given year may indicate that the year is certain but the month and day are not.
  • A date of 1 in a given month may indicate that the year and month are certain but the day is not.

Unless otherwise indicated, for events in England, the date given is Old Style, 10 days behind the Dutch Republic's New Style until 1700 and then 11 days behind.

Date
February 17, 1683 The Royal Society read Letter L-122 of 1683-01-22 to Christopher Wren
February 26, 1683 Francis Aston wrote Letter L-123 of 26 February 1683 about problems translating his letters and opposition to his views
March 9, 1683 Wrote Letter L-124 of 1683-03-09 to Francis Aston promising to send observations about generation and colors
March 27, 1683 Francis Aston wrote Letter L-125 to Leeuwenhoek about new Royal Society officers
May 20, 1683 Wrote Letter L-126 of 1683-05-20 to Anthonie Heinsius about generation and about the circulation of the blood, which he intends to communicate in a letter to the Royal Society
June 7, 1683 Anthoinie Heinsius wrote Letter L-127 to Leeuwenhoek about his observations concerning generation and blood circulation
July 16, 1683 Wrote Letter L-128 of 1683-07-16 to Christopher Wren about the procreation of frogs, sperm in fowl's egg, reproduction of rabbits, little animals in frog intestines, a theory about digestion in humans and fish, and blood
July 22, 1683 Wrote Letter L-129 of 1683-07-22 to Anthonie Heinsius about Heinsius's reactions to an earlier letter
July 28, 1683 The Royal Society read Letter L-128 of 1683-07-16 about reproduction, little animals, digestion, and blood
August 4, 1683 The Royal Society discussed Letter L-128 of 1683-07-16 about the male seed in egg yolks
August 27, 1683 Francis Aston wrote Letter L-130 to Leeuwenhoek, thanking him for his recent letter and agreeing to admit two Dutch noblemen to a meeting of the Royal Society
September 1, 1683 Two Dutch noblemen wrote Letter L-131 some time in early September 1683 to Leeuwenhoek about the fear that kept them from attending a meeting of the Royal Society
September 2, 1683 Wrote Letter L-132 of 1683-09-02 to Anthonie Heinsius, requesting his opinion of observations in Letter L-128
September 10, 1683 Anthonie Heinsius wrote Letter L-133 to Leeuwenhoek about recent observations of generation
September 16, 1683 Wrote Letter L-134 of 1683-09-16 to Anthonie Heinsius about whether Heinsius would like a copy of his speculations on the living organisms in mouths and on the structure of the skin
September 17, 1683 Wrote Letter L-135 of 1683-09-17 to Francis Aston about saliva, nasal hairs and blackheads, skin, pores, calluses, and cleaning teeth; the discovery of bacteria in tartar
September 30, 1683 Wrote Letter L-136 of 1683-09-30 to Anthonie Heinsius, a note accompanying a copy of Letter L-135
October 1, 1683 Melchisédech Thévenot wrote Letter L-138 of October 1683 to Leeuwenhoek, a courteous reply
October 1, 1683 Wrote Letter L-137 of October 1683 to Melchisedec Thévenot with some observations
October 8, 1683 Anthonie Heinsius wrote Letter L-139 of 8 October 1683 to Leeuwenhoek that his work was making a positive impression in Paris and that some of his letters would be published in the new Journal de Médecine
October 11, 1683 Francis Aston wrote Letter L-140 to Leeuwenhoek about the translation of a Dutch phrase concerning egg yolks
October 14, 1683 Wrote Letter L-141 of 1683-10-14 to Anthonie Heinsius in reply to his recent Letter L-139
October 18, 1683 Anthonie Heinsius wrote Letter L-142 of in response to Letter L-141
October 26, 1683 Wrote Letter L-143 of 1683-10-26 to Francis Aston in reply to Letter L-140 about egg yolks
November 3, 1683 The Royal Society read and discussed Letter L-135
November 10, 1683 The Royal Society discussed Leeuwenhoek's observations about pores in the skin in Letter L-135
December 28, 1683 Wrote Letter L-144 of 1683-12-28 to Francis Aston about human skin and its diseases, the intestines, the effects of vinegar, the intestinal wall and peristalsis, and an experiment to demonstrate the adsorption of food nutrients in the intestines.
January 1, 1684 Daniel Gaesbeeck wrote Letter L-145 of 1684-01-01 to Leeuwenhoek about why he was publishing his letters
January 1, 1684 Published Eyerstok (Ovary), Letters 37, 39 (L-122, L-135)
January 1, 1684 Published Humor Cristallinus (Crystalline Humor), Letter 41 (L-147)
January 1, 1684 Published Onsigtbare Geschapene Waarheden (Invisible Creation Truths), Letters 32, 33, 39 (L-108, L-111, L-135)
January 1, 1684 Published Schobbens in de Mond (Scales in the Mouth), Letter 40 (L-144)
January 6, 1684 Authorized as curator to inspect estate of Willemtie Pieters Touw by her heir
February 23, 1684 The Royal Society read Letter L-144 of 1683-12-28 to Francis Aston
March 7, 1684 Francis Aston wrote Letter L-146 to Leeuwenhoek about the importance of his work
April 2, 1684 cousin Margrieta Maertens Leeuwenhoek married Michiel Reijniers van Hasseld
April 14, 1684 Wrote Letter L-147 of 1684-04-14 to Francis Aston about lenses and corneas, the function of eye-lids, the involuntariness of blinking, the optic nerve, and the skin of Moors
May 24, 1684 The Royal Society read the first part of Letter L-147 about the crystalline humour of the eye
May 26, 1684 William Molyneux demonstrated blood flow in a newt to the Dublin Philosophical Society
May 31, 1684 The Royal Society discussed Leeuwenhoek's observations in Letter L-147 about the crystalline humour of the eye
June 7, 1684 Francis Aston wrote Letter L-148 to Leeuwenhoek to thank him for his letter with observations of the lens of the eye, which was read to the Royal Society and was well-received by them
June 14, 1684 The Royal Society read the latter part of Letter L-147 about the crystalline humour of bird and fish eyes, the vitreous humour, the cornea tunica, and the colour of a Blackamore
June 15, 1684 Visited Christiaan Huygens in Den Haag with the Durven brothers
July 24, 1684 Daniel van Gaesbeeck wrote Letter L-149 about why he is publishing more of Leeuwenhoek's “mutilated”, “mistranslated”, and “misunderstood” letters
July 25, 1684 Wrote Letter L-150 of 1684-07-25 to Members of the Royal Society about parts of the brain of several animals, chalk stones of gout, leprosy, and the scales of eels
July 27, 1684 Christiaan Huygens gossiped about Maria Duyst in a letter to his brother Constantijn Huygens
September 15, 1684 Francis Aston wrote Letter L-151 to Leeuwenhoek that Letter L-150 had not been read by the Royal Society
December 13, 1684 sister Catharina Philips Leeuwenhoek received legacy from great uncle Johan Sebastiaans van den Berch
December 13, 1684 The Royal Society read the first part of Letter L-150 about the brain of several animals, chalk stones of gout, leprosy, and scales of eels
December 20, 1684 cousin Geertruijt Huijchs Leeuwenhoek buried
January 1, 1685 cousin Maerten Huijchs Leeuwenhoek appointed tax farmer
January 1, 1685 Published Anatomia et Contemplatio (Anatomy and Contemplation), Letters 43, 42, 38 (L-128, L-150, L-152)
January 1, 1685 Published Onsigtbare Verborgentheden (Invisible Mysteries), Letters 38, 42, 43 (L-152, L-150, L-128)
January 1, 1685 Published Sout-figuren (Salt figures), Letters 44, 45 (L-154, L-157)
January 1, 1685 Published Zaden van Boomen (Seeds of Trees), Letters 46, 47 (L-160, L-166)
January 5, 1685 Wrote Letter L-152 of 1685-01-05 to Members of the Royal Society about salts in wine and vinegar and in the stomach, the eye, the need for food and water, Descartes's theory on smallest water particles, and a theory of taste - salt, sour and sweet
January 17, 1685 The Royal Society read the latter part of Letter L-150 about the brain of an ox and a sparrow, moxa, chalk from gout, leprosy, and eels, in which he discovered both scales and fins
January 20, 1685 Francis Aston wrote Letter L-153 to inform Leeuwenhoek that his recent letter about wine was favorably received at the Royal Society
January 23, 1685 Wrote Letter L-154 of 1685-01-23 to Members of the Royal Society about salts and their crystals and his theory about the causes of taste
January 31, 1685 The Royal Society read the former part of Letter L-152 about salts in vinegar and wine, vinegar eels, and salts found in vinegar mixed with crabs eyes and chalk
February 5, 1685 Visited by Thomas Molyneux on behalf of the Royal Society
February 7, 1685 The Royal Society read and discussed the latter part of Letter L-152 salt in various wines, mixtures of tartar, crabs eyes, or chalk with wine, and the difference between salts in wines and salts in chalk stones of gout
February 13, 1685 Thomas Molyneaux wrote Letter L-155 of 1685-02-13 to Francis Aston about his visit to Leeuwenhoek's house
February 19, 1685 Francis Aston wrote Letter L-156 to inform Leeuwenhoek that his Letter L-154 about salts was received but had not been read to the Society
February 23, 1685 At age 52, his 25th article in Philosophical Transactions
March 30, 1685 Wrote Letter L-157 of 1685-03-30 to Members of the Royal Society about sperm, the uterus of a bitch, sheep embryos, ovaries in young animals and apples, and his claims that sperm are the life-carriers and that there are male and female sperm
April 4, 1685 The Royal Society read the former part of Letter L-154 about salts in wormwood, alum, and other substances
April 20, 1685 At age 52, his 25th letter in Philosophical Transactions
May 9, 1685 The Royal Society read part of Letter L-154 about oil of tartar, potash, and camphor
May 16, 1685 The Royal Society read the latter part of Letter L-154 about salts in ashes, lime, soda, and sal armoniac
May 28, 1685 The Dublin Philosophical Society asked the Royal Society for a copy of Letter L-154 about salts of wine and vinegar
May 31, 1685 Maria Duyst van Voorhout married Frederik Adriaan van Reede van Renswoude
June 20, 1685 The Royal Society read part of Letter L-157 about the role of eggs and male sperm in a female dog
June 22, 1685 Visited by John Locke
June 27, 1685 Francis Aston wrote Letter L-158 of 1685-06-27 to pass along the recommendation by John Hoskyns that Leeuwenhoek examine silkworm eggs
June 27, 1685 The Royal Society read the latter part of Letter L-157 about sperm and eggs in sheep and rabbits
July 2, 1685 sister Catharina Leeuwenhoek appointed as tax collector for three years
July 11, 1685 cousin Adriaen Lambrechts Leeuwenhoek appointed curator
July 13, 1685 Wrote Letter L-159 of 1685-07-13 to members of the Royal Society about reproduction of trees, transfer of nutrients, male and female trees, hazelnut, comparing reproduction of mammals with reproduction of plants, cross-breeding, and germination
July 22, 1685 Royal Society published Letter L-154, titled, “An abstract of a letter from Mr. Leewenheock, to the R. S. Dated Jan. 23rd, 1685; concerning the various figures of the salts contained in several substances”
August 3, 1685 Anthonie Heinsius wrote Letter L-160 to Leeuwenhoek about Robert Boyle's reaction to the letter about cochineal
August 9, 1685 Francis Aston wrote Letter L-161 of some time between August and October 1685 to inform Leeuwenhoek that Letter L-159 had been received but not yet read
August 10, 1685 Wrote Letter L-162 of 1685-08-10 to Anthonie Heinsius about cochineal
August 27, 1685 editor Edmond Halley did not publish any letters by Leeuwenhoek in Philosophical Transactions from 1685 to 1693
August 31, 1685 Anthonie Heinsius wrote Letter L-163 of 1685-08-31 about Boyle's idea about the origin of cochineal
September 21, 1685 Wrote Letter L-164 of 1685-09-21 to Anthonie Heinsius about cochineal
October 1, 1685 Visited by Karl von Hessen-Kassel and Willem Meester sometime in October
October 2, 1685 Karel von Hessen-Kassel wrote Letter L-165 to thank Leeuwenhoek for the visit to his house
October 12, 1685 Wrote Letter L-166 of 1685-10-12 to members of the Royal Society about the beginning of plants in seeds; chyle, sweat, about skin, optic nerve, and bile of fish; salts in beer vinegar and lemon juice; and spirits mixed with blood and wine vinegar
November 5, 1685 Constantijn Huygens Jr. wrote to his brother Christiaan about Leeuwenhoek's character and the visit by Hessen-Kassel and Meester
November 14, 1685 The Royal Society read and discussed Letter L-159 about reproduction of trees, comparison of reproduction of mammals with the reproduction of plants, and cross-breeding
December 1, 1685 Visited by De Saingermain, who later called Leeuwenhoek a "Magus"
December 17, 1685 Constantijn Huygens wrote Letter L-167 to Leeuwenhoek about root trees
December 19, 1685 Francis Aston and Tancred Robinson abruptly resigned as the secretaries of the Royal Society, just a week after they had been reelected
December 25, 1685 cousin Elisabeth Maertens Leeuwenhoek married Dirck van Schie
January 1, 1686 Published Cinnaber Naturalis (Natural Cinnabar), Letters 48 - 52
January 1, 1686 Published Levende Dierkens (Living Animals), Letters 28 - 31, 34 - 36
January 1, 1686 Sat for his oil portrait by artist Johannes Verkolje (1650-1693)
January 22, 1686 Wrote Letter L-168 of 1686-01-22 to members of the Royal Society about cinnabar naturalis, gunpowder, saltpeter, and air made by gunpowder and crab's eyes
January 23, 1686 The Royal Society read part of Letter L-166 about embryo plants in cotton seeds
February 6, 1686 The Royal Society elected Edmond Halley as clerk
March 12, 1686 Edmond Halley wrote Letter L-170, known only by reference in Letter L-176
March 12, 1686 Thomas Gale wrote Letter L-169 to Leeuwenhoek reviewing his recent "ingenious and curious communications"
March 13, 1686 The Royal Society read part of Letter L-166 about chyle, sweat, pores of the skin, the crystalline humour of the eye, and the optic nerve
March 15, 1686 A Prussian doctor wrote Letter L-171 of sometime after 1686-03-15 to request a visit, enclosing pieces of amber
March 16, 1686 Antonio Magliabechi wrote Letter L-172 to Leeuwenhoek, a "most courteous and agreeable letter"
March 20, 1686 The Royal Society read part of Letter L-166 about gall and the scales and slime of fish
March 27, 1686 The Royal Society ordered that the unread part of Letter L-166 be read at the next meeting
April 2, 1686 Wrote Letter L-173 of 1686-04-02 to members of the Royal Society about the structure of bone, the bark of trees, skin and scales, the moisture evaporating from his body, and a little peeling piece of skin
April 3, 1686 The Royal Society asked Francis Lodwick to translate Letter L-168 about cinnebar and gunpowder
April 10, 1686 The Royal Society read and discussed Letter L-168 about cinnebar and gunpowder
April 14, 1686 Wrote letter L-174 of 1686-04-14 to Antonio Magliabechi, now lost
April 24, 1686 The Royal Society ordered that Letter L-173 be translated
May 1, 1686 The Royal Society read part of Letter L-168 about the particles composing cinnabar
May 8, 1686 The Royal Society read another part of Letter L-168 about gunpowder explosions and cannon lengths
May 14, 1686 Wrote Letter L-175 of 1686-05-14 to members of the Royal Society about gall-nuts found on oak trees and the germination of plants
May 22, 1686 The Royal Society read part of Letter L-173 about the structure of cotton seed, the sweat glands of the skin, and the slime of fish
May 25, 1686 Edmond Halley wrote Letter L-176 to Leeuwenhoek about a gift from the Royal Society and requesting some portraits
May 29, 1686 The Royal Society decided to send a gift to Leeuwenhoek, De Historia Piscium by Francis Willughby
June 5, 1686 The Royal Society read part of Letter L-173 about bone and wood
June 8, 1686 Bought a burial section in the Oude Kerk
June 10, 1686 Wrote Letter L-177 of 1686-06-10 to members of the Royal Society about seeds of cotton, kapok, Bupariti, and coconuts, the reproduction of shrimp and lobster, and the eggs of shell fish
June 26, 1686 The Royal Society officers declared their satisfaction with the election of Edmond Halley
July 10, 1686 The Royal Society read part of Letter L-177 about how the leaves, root, and stem are wrapped up with the seeds
July 10, 1686 Wrote Letter L-178 of 1686-07-10 to members of the Royal Society about the growth and durability of wood felled in different seasons and countries, the annual growth rings, and how wooden barrels can be made watertight
July 11, 1686 Jacob Gronovius wrote Letter L-179 to Leeuwenhoek about how his letters were received in Italy
July 17, 1686 The Royal Society ordered that Letter L-178 about the texture of oakwood be translated
September 7, 1686 Examined silkworm eggs
September 10, 1686 Wrote Letter L-180 of 1686-09-10 to Daniël Papenbroek, a cover letter for Letter L-181
September 10, 1686 Wrote Letter L-181 of 1686-09-10 to Antonio Magliabechi, a cover letter for a copy of one of his books
October 30, 1686 Wrote Letter L-182 of 1686-10-30 to Antonio Magliabechi, a cover letter for copies of two of his books
November 5, 1686 Visited by Jacob Gronovius
December 1, 1686 Edmond Halley wrote Letter L-183 to Leeuwenhoek on behalf of the Royal Society, now lost
January 1, 1687 cousin Maarten Pieters Hogenhouck (1650-1720) appointed to Veertigraad, served 1687-1720
January 1, 1687 Published Anatomia Seu Interiora Rerum (Interior Anatomy), 19 Letters from 28 - 52
January 1, 1687 Published Anatomia Seu Interiora Rerum (Interior Anatomy), Letters 43, 42, 38
January 1, 1687 Published Vervolg der Brieven (Continuation of the Letters), Letters 53 - 60
January 27, 1687 cousin Magdaleentje (Helena) Maertens Leeuwenhoek married Barent van Frijtom
February 24, 1687 Edmond Halley wrote Letter L-184 to Leeuwenhoek on behalf of the Royal Society, assuring him that the portraits he sent are received, wondering why he has not sent any observations recently, and enclosing recent numbers of Philosophical Transactions
March 1, 1687 Wrote Letter L-185 of 1687-03-01 to James II, King of England, as the dedication for one of his volumes
March 28, 1687 mentor Constantijn Huygens died
April 4, 1687 Wrote Letter L-186 of 1687-04-04 to the members of the Royal Society about the structure of the teeth of elephants, pigs, humans, oxen, and horses and about toothache
April 5, 1687 Guarantor for Johan Francisco de Raet when he became a citizen of Delft
April 16, 1687 The Royal Society ordered that Letter L-186 about teeth be translated
April 23, 1687 The Royal Society read part of Letter L-186 about the structure of teeth
May 7, 1687 The Royal Society read the latter part of Letter L-186 about the teeth of various animals
May 9, 1687 Wrote Letter L-187 of 1687-05-09 to members of the Royal Society about the structure of 'stone' of the medlar and the coffee bean and acid in plants
May 14, 1687 The Royal Society read and discussed part of Letter L-187 about embryo plants in seeds
June 4, 1687 The Royal Society read and discussed part of Letter L-187 about coffee
June 11, 1687 cousin Adriaen Lambrechts Leeuwenhoek admitted as notary
June 13, 1687 Wrote Letter L-188 of 1687-06-13 to members of the Royal Society about wheat and the seeds from a variety of plants
June 18, 1687 The Royal Society read part of Letter L-175 about gall nuts, over a year after receiving it
July 11, 1687 Wrote Letter L-189 of 1687-07-11 to members of the Royal Society about eggs of silkworms and caterpillars and humans' squinting and a theory for its cause
August 6, 1687 Wrote Letter L-190 of 1687-08-06 to members of the Royal Society about the calander and the louse and against spontaneous generation
August 6, 1687 Wrote Letter L-191 of 1687-08-06 to Robert Boyle about his recent letters
September 9, 1687 Wrote Letter L-192 of 1687-09-09 to members of the Royal Society about ant eggs, larvae and its development, feeding, sting, cocoon and nest
October 7, 1687 Appointed curator of the insolvent estate of Evert van der Sijde
October 17, 1687 Wrote Letter L-193 of 1687-10-17 to members of the Royal Society about amber, 'burned paper' from the sky, rotifers, maggots, blow flies, the stinging hairs of nettles, and the East-Indian centipede
November 24, 1687 nephew Johannes Adriaans Swalmius married Magdelena van Mierop
November 26, 1687 The Royal Society read part of Letter L-192 about the generation of ants
November 28, 1687 Wrote Letter L-194 of 1687-11-28 to members of the Royal Society about his discovery that cochineal was an insect and his experiments with cinchona bark
December 3, 1687 The Royal Society read and discussed the latter part of Letter L-192 about the generation of ants
December 11, 1687 The Royal Society ordered that Letter L-194 be translated
January 1, 1688 Published Vervolg der Brieven (Continuation of the Letters), Letters 53 - 60 (2nd)
January 1, 1688 Wrote Letter L-195 of sometime in 1688 to Robert Boyle, now lost
April 2, 1688 printer-bookseller Hendrik van Cronevelt bought the house next door
May 25, 1688 Wrote Letter L-196 of 1688-05-25 to members of the Royal Society about a medicinal root and bladderstones
July 6, 1688 Wrote Letter L-197 of 1688-07-06 to the members of the Royal Society bezoar stone, monkey stone, gout tubercles, and red coral and white coral
August 3, 1688 Wrote Letter L-198 of 1688-08-03 to the members of the Royal Society about plaster, alabaster, gypsum, Muscovite glass, cobblestone, shell lime, masonry mortar, lime, cement, sand stone, and slate
August 24, 1688 Wrote Letter L-199 of 1688-08-24 to the members of the Royal Society about gnats, horseflies; growth of branches, germination of wheat plants, the soft and hard roe of cod, and the number of sperm in a cod's soft roe
September 7, 1688 Wrote Letter L-200 of 1688-09-07 to the members of the Royal Society
September 15, 1688 Published Den Waaragtigen Omloop des Bloeds (On the True Circulation of Blood), Letter 65 (L-200)
September 23, 1688 Wrote Letter L-201 of 1688-09-23 to Melchisedec Thevenot, a cover letter for a copy of Leeuwenhoek's Letter L-200, published separately as Den waaragtigen omloop des bloeds.
January 1, 1689 Published Continuatio Epistolarum (Continuation of the Letters), Letters 53-60
January 1, 1689 Published Tweede Vervolg der Brieven (Second Continuation of the Letters), Letters 61 - 67
January 1, 1689 Wrote Letter L-202 of sometime in 1689 to Antonio Magliabechi, a cover letter for one of his books
January 12, 1689 Wrote Letter L-203 of 1689-01-12 to Robert Boyle, a cover letter for Continuatio epistolarum and a copy of Letter L-204
January 12, 1689 Wrote Letter L-204 of 1689-01-12 to the members of the Royal Society about his observation of the circulation of the blood in a variety of fish as well as a description of the construction of his ‘eel spy-glass’ and the slime on the skin of an eel
March 6, 1689 Christiaan Huygens wrote Letter L-205 to Leeuwenhoek, thanking him for the gift of a mangrove tree and inquires whether L.’s observations of the circulation of the blood could also be seen in the wings of bats, the legs of ducks, and the ears of rats
April 1, 1689 Did not write any letters between 1689 04-01 and 1691 09-18
April 1, 1689 Wrote Letter L-206 of 1689-04-01 to the members of the Royal Society
April 23, 1689 Appointed guardian of the children of Jacob Bellart
May 27, 1689 Anthonie Heinsius became Grand Pensionary of the States of Holland
June 21, 1689 nephew Adriaan Johannes Swalmius baptized, witnessed by Antony and Cornelia
October 1, 1689 Wrote Letter L-207 of October 1689 to Christiaan Huygens about sending books to father Constantijn Huygens in London
October 19, 1689 cousin Adriaen Lambrechts Leeuwenhoek married Eva Jacobs Overschie
March 6, 1690 Christiaan Huygens wrote Letter L-208 to Leeuwenhoek about liquids in glass balls and Iceland crystal
April 3, 1690 cousin Maarten Lambrechts Leeuwenhoek married Margareta Pieters van Limburg
April 17, 1690 daughter Maria made a will
September 7, 1690 Bought the other part of the garden outside the walls of the city
January 1, 1691 Published Onsigtbare Verborgentheden (Invisible Mysteries), Letters 38, 42, 43 (2nd)
March 2, 1691 Gottfried Leibniz wrote to Christiaan Huygens praising Leeuwenhoek, "who tells me what he observes"
May 27, 1691 Antonio Magliabechi wrote Letter L-209 of 1691-05-27 to Leeuwenhoek about book news and Leibniz's reaction to some of Leeuwenhoek's observations
September 18, 1691 Wrote Letter L-210 of 1691-09-18 to Antonio Magliabechi about
September 21, 1691 William Stanley wrote Letter L-211 of 1691-09-21 to Leeuwenhoek, a courtesy letter
November 27, 1691 Wrote Letter L-212 of 1691-11-27 to the members of the Royal Society about blood, chyle, and an experiment to discover the volume of water when it is cold and when it is heated
December 2, 1691 mentor Cornelis 's Gravesande died
December 5, 1691 mentor Cornelis 's Gravesande buried
December 6, 1691 brother-in-law Jan Jacobs de Molijn buried
January 1, 1692 William Molyneaux wrote about a visit to Leeuwenhoek
January 4, 1692 Wrote Letter L-213 of 1692-01-04 to the members of the Royal Society about bladder and kidney stones and a chalk-like substance from a gout stone
January 13, 1692 niece Geertruijt Jans de Molijn inherited property from her father Jan Jacobs
February 1, 1692 Robert Hooke called Leeuwenhoek the microscope's "single votary"
February 1, 1692 Wrote Letter L-214 of 1692-02-01 to the members of the Royal Society about various peppers and their taste, tea and its effects of tea on digestion, and Spanish fly
February 12, 1692 Richard Waller wrote Letter L-215 to Leeuwenhoek about his recent observations and the structure of grass
March 7, 1692 Wrote Letter L-216 of 1692-03-07 to the members of the Royal Society about corn-weevels, corn-moths, caterpillars, butterflies, calanders, lice in corn-lofts, little animals in rain water, black-flies in blossoms, and maggots in cheese
March 19, 1692 Reimbursed for purchase of distilled water and wine
April 22, 1692 Wrote Letter L-217 of 1692-04-22 to Richard Waller about the construction of an air pump and experiments with different liquids, seeds and small stones in urine, a hog's hair in the skin of a child, and grains of wheat
June 24, 1692 Antonio Magliabechi wrote Letter L-219 of 1692-06-24 to Leeuwenhoek about recent books that he thought might be of interest by Ramazzini and Guiglielmini
June 24, 1692 Wrote Letter L-218 of 1692-06-24 to the members of the Royal Society about more experiments with his air-pump, the structure of and blood in an insect's wing, a grey owlet moth, and the wing of a very small fly
July 22, 1692 Christiaan Huygens began second series of observations of microbes replicating and expanding on Leeuwenhoek's
August 12, 1692 Wrote Letter L-220 of 1692-08-12 to the members of the Royal Society about the shaft of a bird's feather as used in a quill, the lens and cornea of the human and calf eyes, 'wood-pipes' in different species of wood, bulrushes, and pine and lime wood
September 16, 1692 Wrote Letter L-221 of 1692-09-16 to the members of the Royal Society about little animals in dental tartar, theories of eel reproduction, worms in eel intestines, and blood vessels in grasshoppers
September 23, 1692 Wrote Letter L-222 of 1692-09-23 to Mary, Queen of Great Britain, the dedication to Derde Vervolg der Brieven
October 20, 1692 Christiaan Huygens wrote Letter L-223 to Leeuwenhoek about the procreation of eels and spontaneous generation and praised his work and diligence
November 29, 1692 cousin Sara Maertens Leeuwenhoek married Cornelis Luda
December 21, 1692 cousin Jacob Adriaens Leeuwenhoek (1692-1724) baptized
February 28, 1693 editor Richard Waller began publishing Leeuwenhoek again in Philosophical Transactions
March 25, 1693 Published Derde Vervolg der Brieven (Third Continuation of the Letters), Letters 68 - 75
April 4, 1693 Received an honorarium from the city for his books of letters
May 8, 1693 Richard Waller wrote Letter L-224 to Leeuwenhoek about colors of feathers and univocal generation
May 23, 1693 De la Croze called Leeuwenhoek a "curious Observer of Nature"
July 1, 1693 Wrote Letter L-225 of 1693-07-01 to Richard Waller, cover letter for a volume in Latin and confirmation of receipt of Letter L-224
August 18, 1693 Pieter Rabus wrote Letter L-226 to Leeuwenhoek praising his accomplishments and including a laudatory poem
September 3, 1693 George Garden wrote Letter L-227 to Leeuwenhoek about the role of egg and ovaries in reproduction
September 18, 1693 Paul Durven appointed curator
September 26, 1693 cousin Sara Maertens Leeuwenhoek buried
September 30, 1693 Edmund King replicated Leeuwenhoek's observations of little animals in pepper water
October 15, 1693 Wrote Letter L-228 of 1693-10-15 to the members of the Royal Society about colors and the life cycle of fleas
October 27, 1693 Wrote Letter L-229 of 1693-10-27 to Pieter Rabus about procreation of the flea, the leather-jacket, and the mite
November 19, 1693 nephew Johannes Adriaans Swalmius buried
November 21, 1693 Appointed guardian of his dying wife Cornelia Swalmius
November 30, 1693 Hans Sloane was elected Secretary of the Royal Society and editor of Philosophical Transactions, publishing 68 articles by Leeuwenhoek over the next twenty years
December 5, 1693 Rented St. Agnieten Tooren from the city for 12 years
December 7, 1693 wife Cornelia Swalmius made a will
December 8, 1693 Wrote Letter L-230 of 1693-12-08 to Richard Waller, a cover letter
December 20, 1693 Wrote Letter L-231 of 1693-12-20 to the members of the Royal Society about spiders, lice, and mites
December 26, 1693 wife Cornelia Swalmius made a will including Maria
December 29, 1693 Sold the garden outside the walls of the city
December 31, 1693 Promised to pay five gulden for the ransom of a neighbor's son from Algerian pirates
January 1, 1694 Published Onsigbare Geschapene Waarheden (Invisible Creation Truths), Letters 32, 39, 33
January 1, 1694 Published Vierde Vervolg der Brieven (Fourth Continuation of the Letters), Letters 76 - 83
January 6, 1694 wife Cornelia Johannes Swalmius buried
January 19, 1694 Wrote Letter L-232 of 1694-01-19 to Richard Waller as a cover letter for Letter L-231
January 24, 1694 Wrote Letter L-233 of 1694-01-24 to the members of the Royal Society about tapeworms and salt and sand in cod intestines
February 10, 1694 Richard Waller wrote Letter L-234 to Leeuwenhoek, asking him to examine the colors of birds' feathers and other bodies, such as silk, paint, and mercury and whether he had observed sperm inside of an egg
February 12, 1694 Presented act of guardianship to the Weeskamer after Cornelia's death
February 12, 1694 Wrote Letter L-235 of 1694-02-12 to Richard Waller as a cover letter for Letter L-233
February 24, 1694 Wrote Letter L-236 of 1694-02-24 to the members of the Royal Society about his experiments with solid phosphorus
February 28, 1694 Benedictus Haan wrote Letter L-237 to Leeuwenhoek agreeing with him against George Garden about the female ovary
March 2, 1694 Antonio Magliabechi wrote Letter L-238 of sometime before 1694-03-02 to Leeuwenhoek about recent books that he thought might be of interest
March 2, 1694 Presented Cornelia's will to the Weeskamer
March 2, 1694 Wrote Letter L-239 of 1694-03-02 to the members of the Royal Society about ear wax and hair, body hair, the amount of sweat secreted from the human body, and the possibility that sperm might penetrate the ovum
March 19, 1694 Wrote Letter L-240 of 1694-03-19 to the members of the Royal Society refuting George Garden's ideas in Letter L-227 about the role of the ovary and eggs
April 2, 1694 Wrote Letter L-241 of 1694-04-02 to the members of the Royal Society about the tongue of an ox and a pig and the heart of a sheep, ox, duck, chicken and cod
April 30, 1694 Wrote Letter L-242 of 1694-04-30 to the members of the Royal Society about his criticisms of Buonanni's theory of spontaneous generation, about mussels, barnacles, shrimp larvae, the eye of a dragon-fly, gnat, fly, and ant, and about ant eggs
May 2, 1694 Richard Waller wrote Letter L-243 to Leeuwenhoek about recent observations, to request a portrait, and to introduce Mr. Walfort, who delivered it
May 11, 1694 Received an honorarium from the city for Vierde Vervolg der Brieven (Fourth Continuation of the Letters)
May 26, 1694 Wrote Letter L-244 of 1694-05-26 to Richard Waller, cover letter for copy of Vierde Vervolg der Brieven
June 4, 1694 Visited Pieter Rabus in Rotterdam
July 7, 1694 Royal Society accepted gift of Vierde Vervolg der Brieven and read Leeuwenhoek's cover letter, Letter L-244
July 30, 1694 Arnold Ramp appointed tax collector for livestock sales
September 14, 1694 Wrote Letter L-245 of 1694-09-14 to Richard Waller about blood circulation and having sent six copies of his portrait to London
November 3, 1694 Lent 400 guilders to Leendert van Bijstervelt
November 24, 1694 cousin Maerten Huijchs Leeuwenhoek buried
November 29, 1694 microscopist Marcello Malpighi died
November 30, 1694 Wrote Letter L-246 of 1694-11-30 to Pieter Rabus about about dragon-fly eyes and eggs, crab eyes, vertebrate corneas, another rejection of spontaneous generation, and the impregnation of women
January 1, 1695 Published Arcana Naturae Detecta (Nature's Mysteries Disclosed), Letters 32, 33, 37, 39 - 41, 61 - 92
January 1, 1695 Published Register van alle de Werken, Letters 28 - 83
April 10, 1695 Wrote Letter L-247 of 1695-04-10 to Anthonie Heinsius about blood and its circulation in a crab's leg, crystals in evaporated crab blood, and the hairs on a crab's leg
April 22, 1695 Wrote Letter L-248 of 1695-04-22 to Frederik Adriaan van Reede about the apple-blossom weevil, its larvae, their danger, and their metamorphosis and the reproduction of black flies on apple tree blossoms
April 30, 1695 Bought bonds and annuities from the city of Delft
May 1, 1695 Frederick Adriaan van Reede wrote Letter L-249 sometime in early May 1695 that he was pleased with Leeuwenhoek’s observations about the apple-blossom weevil and black flies on apple tree blossoms
May 1, 1695 Pieter Rabus wrote Letter L-250 to Leeuwenhoek, a "pleasant" letter now lost
May 1, 1695 Wrote Letter L-251 of 1695-05-01 to Anthonie Heinsius about weevils, nutmegs and their safe storage, and tobacco seeds and their germination
May 2, 1695 Maarten Etienne van Velden wrote Letter L-252 to Leeuwenhoek about two printed works and a box of flies
May 18, 1695 Wrote Letter L-253 of 1695-05-18 to Frederik Adriaan van Reede about the apple-blossom weevil, caterpillars and the metamorphosis of the small ermine moth, and parasitic flies
May 21, 1695 Wrote Letter L-254 of 1695-05-21 to Pieter Rabus about the eggs and blood vessels of the ray
May 23, 1695 Wrote Letter L-255 of 1695-05-23 to Maarten Etienne van Velden about the impossibility of small flies being generated from the body of a big dead caterpillars, again refuting the theory of spontaneous generation
May 30, 1695 Maarten Etienne van Velden wrote Letter L-256 about his dissatisfaction with Leeuwenhoek's views on spontaneous generation in Letter L-255
June 1, 1695 Frederick Adriaan van Reede wrote Letter L-257 sometime in June 1695 that he was pleased with Leeuwenhoek’s further observations about garden pests
June 21, 1695 Pieter Rabus wrote Letter L-258 asking for Leeuwenhoek’s comments on a letter he had received about caterpillars that were growing in a woman’s ears
June 28, 1695 Visited by Johann Wilhelm von Pfalz-Neuburg, Elector Palatine, his wife and his mother
July 1, 1695 A doctor from Zeeland, Angelus van Wijkhuysen, wrote Letter L-259 to request Leeuwenhoek's opinion on the origin of flies from a dead caterpillar
July 8, 1695 Christiaan Huygens died
July 10, 1695 Wrote Letter L-260 of 1695-07-10 to Frederik Adriaan van Reede about aphids, their reproduction, and the unsuccessful search for male aphids
July 12, 1695 Wrote Letter L-261 of 1695-07-12 to Maarten Etienne van Velden about the metamorphosis of caterpillars and of parasitic larvae coming out of a dead caterpillar
July 20, 1695 Wrote Letter L-262 of 1695-07-20 to Anthonie Heinsius about about scales from his own skin, wool threads from his stockings, salt from his sweat, and air bubbles and salt crystals from his ear wax
July 21, 1695 Wrote Letter L-263 of 1695-07-21 to Pieter Rabus about the report that a large caterpillar emerged from a woman's ear and fumigation with sulphur to remove it; Leeuwenhoek cannot find any mites in his own auditory canal
August 15, 1695 Wrote Letter L-264 of 1695-08-15 to Frederik Adriaan van Reede about oysters and their larvae, repudiating spontaneous generation
August 15, 1695 Wrote Letter L-265 of 1695-08-15 to Antonio Magliabechi, the dedication of Arcana Naturae Detecta
August 16, 1695 Wrote Letter L-266 of 1695-08-16 to inform Antonio Magliabechi that he has dedicated Arcana Naturae Detecta to him; he mentions the visit of the Elector Palatine
August 18, 1695 Wrote Letter L-267 of 1695-08-18 to Anthonie Heinsius about detonating gunpowder in a closed glass bulb and measuring the increase in volume after the explosion; in a partial vacuum, glass bulbs may implode
August 20, 1695 Wrote Letter L-268 of 1695-08-20 to Frederik Adriaan van Reede about again about oysters and their sperm and aphids and other parasites
September 1, 1695 A certain gentleman, Angelus van Wijkhuysen, wrote Letter L-269 before September 1695 to inform Leeuwenhoek about mussel gatherers and a minister who believed that mussels are formed by spontaneous generation
September 10, 1695 Wrote Letter L-270 of 1695-09-10 to Pieter Rabus about his attempt to breed maggots with his own ear-wax as food and a movement in his ear due to the vibration of a little hair against the ear-drum
September 18, 1695 Wrote Letter L-271 of 1695-09-18 to Johann Wilhelm von Pfalz-Neuburg about swan mussel sperm, eggs, embryos, and locomotion, small animals as food for larger ones and oysters and their larvae; he again refutes spontaneous generation
October 12, 1695 Antonio Magliabechi wrote Letter L-272 of 1695-10-12 to thank Leeuwenhoek for dedicating Arcana Natura Detecta to him and to report on several recent books written in Latin and Italian by Italians that he thought might be of interest
October 14, 1695 Antonio Magliabechi wrote Letter L-273 to praise Leeuwenhoek
October 18, 1695 Wrote Letter L-274 of 1695-10-18 to Antonio Magliabechi to accompany a parcel of books, which Leeuwenhoek gave to Baron Bettino Riasoli for delivery

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