Letters written by Leeuwenhoek during Period 4

Alle de Brieven / Collected Letters has over 350 letters. However, only those in this chronology that Leeuwenhoek designated Letter 1, Letter 2, etc. did he consider to contain publishable microscopic observations.

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 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
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
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 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
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 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 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
October 31, 1695 Wrote Letter L-276 of 1695-10-31 to Magliabechi to acknowledge the receipt of Magliabechi's Letter L-272, to report on the books he sent and on his recent Letter L-271 to Johann Wilhelm von Pfalz-Neuburg
October 31, 1695 Wrote Letter L-277 of 1695-10-31 to Jacob Calckberner to request that he forward a package of books to Magliabechi
November 3, 1695 Wrote Letter L-279 of 1695-11-03 to Johann Wilhelm von Pfalz-Neuburg about larvae from swan mussels, little animals in water taken out of swan mussels, and extracts from letters to Oldenburg and Brouncker about the quantity of little animals
December 1, 1695 Wrote Letter L-281 of 1695-12-01 to Frederik Adriaan van Reede, the dedication of the Fifth Continuation of the Letters (Vijfde Vervolg der Brieven)
December 22, 1695 Wrote Letter L-282 of 1695-12-22 to acknowledge the receipt of two letters by Magliabechi and to tell him once again that the books have been forwarded to him
December 28, 1695 Wrote Letter L-283 of 1695-12-28 to Hendrik van Bleyswijk about herring, their stomach worms, the food in herring stomachs, and how small fish like herring catch food
February 20, 1696 Wrote Letter L-285 of 1696-02-20 to Frederik Adriaan van Reede about the anatomy of the body louse, especially the sexual organs and the louse's rapid reproduction, and his opposition to Jonston's and Kircher's observations on lice
March 8, 1696 Wrote Letter L-287 of 1696-03-08 to Nicolaas Witsen about white mace caused by vermin, a moth from a larva taken from mace, larvae and wings of the merchant grain beetle, and nutmeg; warehouses should be painted to protect spices from vermin
June 1, 1696 Wrote Letter L-289 of 1696-06-01 to Pieter Rabus about dowsing rods and the hazel branches used to make them, iron, and loadstone
July 6, 1696 Wrote Letter L-292 of 1696-07-06 to Nicolaas Witsen about his analysis of the mineral that Witsen sent with Letter L-291, ant stings, and lacquer particles on a tree that originate from the tree itself, not from ants
July 10, 1696 Wrote Letter L-294 of 1696-07-10 to Nicolaas Witsen about demonstrating the rotation of the earth with the aid of a glass globe filled with water in which wax particles are floating.
July 10, 1696 Wrote Letter L-295 of 1696-07-10 to the members of the Royal Society about the circulation of blood in eels; mites, figs, strawberries, and a lobster's leg; a transcription of Christiaan Huygens's Letter L-223 about the reproduction of eels
July 16, 1696 Wrote Letter L-296 of 1696-07-16 to Frederik Adriaan van Reede about the male and female sexual organs of oysters and their larvae
July 23, 1696 Wrote Letter L-297 of 1696-07-23 to Pieter Rabus honey-dew on lime-trees; moisture from vine tendrils leads to a theory on the production of lacquer in tropical trees; his Delft friend has lost the capacity to handle the dowsing-rod
August 26, 1696 Wrote Letter L-300 of 1696-08-26 to Frederik Adriaan van Reede about plant-lice, its embryos and parasitization, black flies and their caterpillars on apple-trees, and English oysters from Zierikzee
August 28, 1696 Wrote Letter L-301 of 1696-08-28 to Antonio Magliabechi to acknowledge receipt of Letter L-293, to inquire about the reaction of the grand duke to his work, and to thank Magliabechi for sending printed matter and book news from Italy
August 29, 1696 Wrote Letter L-302 of 1696-08-29 to Hendrik van Bleyswijk about oak-wood containing beetle larvae, which appeared to be able to feed on wood, and the cause of the differences in quality of oak-wood
September 7, 1696 Wrote Letter L-303 of 1696-09-07 to thank Magliabechi for Letter L-290 of 5 June and Letter L-293 of 8 July 1696 and to request that Magliabechi spare him exaggerated praise henceforth
September 12, 1696 Wrote Letter L-304 of 1696-09-12 to Anthonie Heinsius about rennet and curd, chalk and crab's-eyes in vinegar, smoking tobacco to cure toothache, the gall-bladder and omasum of a calf, milk-clotting, and his contradiction of a physician
September 27, 1696 Wrote Letter L-305 of 1696-09-27 to Hendrik van Bleyswijk about the age of fishes, especially herring, using scales and the structure of greater weever's spine and the painfulness of its sting
October 26, 1696 Wrote Letter L-306 of 1696-10-26 to Maarten Etienne van Velden to accompany a presentation copy of his printed letters, Sesde Vervolg Der Brieven (Sixth Continuation of the Letters)
October 30, 1696 Wrote Letter L-307 of 1696-10-30 to a "gentleman in Brabant", a cover letter accompanying a copy of Sesde Vervolg der Brieven
November 15, 1696 Wrote Letter L-309 of "latter part" of 1696 to Harmen van Zoelen about what I had learned from an East India Trader
February 12, 1697 Wrote Letter L-314 of 1697-02-12 to Maarten Etienne van Velden, regretting Van Velden's difficulties caused by his defence of Copernicus and in support, enclosing a copy of a letter from a gentleman in Brabant
February 19, 1697 Wrote Letter L-315 of 1697-02-19 to Hans Sloane about sending Sesde Vervolg der Brieven and wanting to receive the latest Philosophical Transactions and the works of Malpighi
March 25, 1697 Wrote Letter L-316 of 1697-03-25 to the members of the Royal Society as a cover letter to Continuatio Arcanorum Naturae
April 5, 1697 Wrote Letter L-318 of 1697-04-05 to the members of the Royal Society about experiments with magnets, a meniscus in a glass, and patients given 'sympathetic' powder as a medicine by a German quack doctor
May 15, 1697 Wrote Letter L-320 of May 1697 to Victor van Beughem about how to distribute the enclosed copies of Continuatio Arcanorum Naturae
June 6, 1697 Wrote Letter L-323 of 1697-06-06 to Antonio Magliabechi about marine fossils found in mountain rocks and the present of copies of Continuatio Arcanorum Naturae sent to Florence
July 1, 1697 Wrote Letter L-324 of 1697-07-01 to Luca Giamberti to request that he send Magliabechi's gift book by a freighter from Cologne via Düsseldorf to Dordrecht
September 3, 1697 Wrote Letter L-328 of 1697-09-03 to Jan van Leeuwen about ears of wheat with smut and a theory of fungous disease in grain; refutes the notion that honey-dew causes smut ears
September 10, 1697 Wrote Letter L-329 of 1697-09-10 to the members of the Royal Society about small white eggs mixed with earth, a pulsating pulmonary vein in an egg, Roman snails, the rootlets of a wheat grain, one of his own teeth, and young oysters
November 2, 1697 Wrote Letter L-330 of 1697-11-02 to Antonio Magliabechi to thank him for two of his letters and to complain that the book sent to him has not yet arrived
January 1, 1698 Wrote Letter L-331 of sometime between late December 1697 and mid-January to Johan Arnoldi about the book that Magliabechi had sent
January 19, 1698 Wrote Letter L-334 of 1698-01-19 to Govert Bidloo about how little animals get into the human body through canal water and food preparation
February 10, 1698 Wrote Letter L-335 in February 1698 to Johan Arnoldi that he should do whatever it takes to get the book that Magliabechi sent and that he will reimburse whatever it costs
February 20, 1698 Wrote Letter L-336 of 1698-02-20 to Antonio Magliabechi about problems during the transport of the book that Magliabechi had sent to Leeuwenhoek as a present
April 15, 1698 Wrote Letter L-341 around April 1698 to Harmen van Zoelen about using plaster to whitewash wooden storage containers to prevent damage from worms
April 17, 1698 Wrote Letter L-342 of 1698-04-17 to Antonio Magliabechi that the book had at last arrived and received a place of honour in his house
May 9, 1698 Wrote Letter L-343 of 1698-05-09 to the members of the Royal Society about the compound eye of a beetle and the number of facets, the human cornea, drone flies, and gnat brains and leg muscles
August 14, 1698 Wrote Letter L-346 of 1698-08-14 to Antonio Magliabechi about payment for and arrival of a book sent by Magliabechi as a present as well as an enclosed catalogue of an art collection of the Mennonite minister A. van Beusecom
September 20, 1698 Wrote Letter L-347 of 1698-09-20 to Anthonie Heinsius about blood circulation in an eel's tail, the transition of arterial into venous capillaries, and the connection between the thickness of the wall of the blood vessels and the viscosity of the blood
December 17, 1698 Wrote Letter L-349 of 1698-12-17 to Harmen van Zoelen to defend himself against Hartsoeker's claim to have been the first to discover sperm
February 1, 1699 Wrote Letter L-352 of 1699-02-01 to a "right honorable sir" about his inspection of a mineral containing gold and silver from the Salida mine in Sumatra; his theory about the formation of gold and silver ores
February 15, 1699 Wrote Letter L-353 of February 1699 to Johan Arnoldi about how he can repay Leeuwenhoek
February 28, 1699 Wrote Letter L-354 of 1699-02-28 to Antonio Magliabechi about reimbursement for Arnoldi's expenses for the book that Leeuwenhoek finally received
April 26, 1699 Wrote Letter L-355 of 1699-04-26 to Harmen van Zoelen about the damage caused to mace by insects and their larvae, damage to bamboo, and the biting and stinging of noxious white ants and the struggle against them by chalking of wood
June 9, 1699 Wrote Letter L-356 of 1699-06-09 to the members of the Royal Society to dispute Dalenpatius's 'Nouvelles de la Republique des lettres', in which sperm are described as having the shape of the human body
June 23, 1699 Wrote Letter L-357 of 1699-06-23 to the members of the Royal Society in response to Martin Lister's objections against his theory of generation; his opposition to the theory of spontaneous generation; the assumption of male and female spermatozoa
August 5, 1699 Wrote Letter L-358 of 1699-08-05 to the directors of the United East India Company in Delft about circulation of the blood in the leg of a scorpion from India that they had sent to him; a description of the eight eyes and the pincers
September 25, 1699 Wrote Letter L-360 of 1699-09-25 to Hans Sloane to request a reaction to previously sent letters and as cover letter for Letter L-361 of the same day to the Royal Society
September 25, 1699 Wrote Letter L-361 of 1699-09-25 to the members of the Royal Society about the circulation of blood in tadpole capillaries, the transition from arteries to veins, blood clotting, the dissolution of clotted blood, and the origin of the name thunder-pad
October 1, 1699 Wrote Letter L-362 of sometime in October 1699 to Ehrenfried von Tschirnhaus about medicines, his aversion to bleeding and purging, and his preference for tea and coffee as medicine; credulity of people who trust impostors and poorly trained physicians
October 16, 1699 Wrote Letter L-363 of 1699-10-16 to Antonio Magliabechi about tiny animalcules from ditchwater, his opposition to spontaneous generation, and how animals serve as food for each other
January 2, 1700 Wrote Letter L-364 of 1700-01-02 to Hans Sloane about liver fluke, gnat larvae, circulation of blood in a frog, and little animals in its feces
January 14, 1700 Wrote Letter L-365 of 1700-01-14 to Nicolaes Boogaert van Belois about blood circulation in lizard legs, the way a lizard and a scorpion react to one another, the scorpion's eyes, pincers, and sting and the muscle fibres in that sting
May 20, 1700 Wrote Letter L-366 of 1700-05-20 to Hendrik van Bleyswijk about the eyes and the sting of a centipede and the reactions of a fly and a lizard to a centipede
May 20, 1700 Wrote Letter L-367 of 1700-05-20 to Anthonie Heinsius about peat, its composition and origin, how much soil washed into the sea by rivers and effect on sea level compared to amount of soil lost through peat cutting
June 2, 1700 Wrote Letter L-368 of 1700-06-02 to Frederik Adriaan van Reede about the eyes, mouth parts, food, intestines, and eggs of a shrimp
June 14, 1700 Wrote Letter L-370 of 1700-06-14 to answer Hans Sloane's Letter L-369 that he has examined the sperm of many animals, but if there is any animal that the Royal Society would like him to investigate, he will do so.
June 16, 1700 Wrote Letter L-371 of 1700-06-16 to a "Highly Learned Sir" summarizing his earlier investigations of bees, especially the queen bee and her eggs, and of the propagation of other insects
July 9, 1700 Wrote Letter L-372 of 1700-07-09 to Hans Sloane about red blood cells in flounder and salmon, how their oval form changes shape to pass through capillaries, and the sperm of a young cock
July 10, 1700 Wrote Letter L-373 of 1700-07-10 to Anthonie Heinsius about seeds of plants and parts of invertebrates in peat found near Hellevoetsluis
July 27, 1700 Wrote Letter L-375 of 1700-07-27 to Hans Sloane about experiments with the larvae of cheese flies received from Sloane a week earlier and the treatment of his wife's toothache with vitriol
August 1, 1700 Wrote Letter L-376 of 1700-08-01 to "Your Most Serene Highness" about the influence of atmospheric pressure on the level of a water column in a glass tube during a capillary rise; comparison to the column of mercury in a barometer
September 7, 1700 Wrote Letter L-377 of 1700-09-07 to Hans Sloane to follow up on Letter L-375 to Sloane about fly larvae in cheese
October 26, 1700 Wrote Letter L-378 of 1700-10-26 to Hans Sloane about black flies on fruit trees, aphids, comparing the parthenogenetic procreation of aphids with sperm, and the development of the pupae of moths
December 25, 1700 Wrote Letter L-380 of 1700-12-25 to Hans Sloane about the sperm of a ram and his objections to Nicolaas Hartsoeker's claim to have discovered sperm first in 1678 when Leeuwenhoek had written to the Royal Society about sperm in 1677
January 28, 1701 Wrote Letter L-382 of 1701-01-28 to Hans Sloane about gall on a willow and more about larvae from cheese
February 9, 1701 Wrote Letter L-383 of 1701-02-09 to Frederik Adriaan van Reede about pores in willow wood and advice for the improvement of peat
April 8, 1701 Wrote Letter L-384 of 1701-04-08 to the mayors of Delft about his calculation of the difference between the coal measures of Delft and Rotterdam and how to calculate the volume of a pyramid
April 15, 1701 Wrote Letter L-385 of 1701-04-15 to the members of the Royal Society about sperm from cod, a calculation of its size, and ram and pike sperm
June 21, 1701 Wrote Letter L-389 of 1701-06-21 to John Chamberlayne about salt crystals in rain-water and notches in a sharpened knife
June 21, 1701 Wrote Letter L-390 of 1701-06-21 to the members of the Royal Society about spiders, their blood, their silk thread and its structure, their sting, and laying their eggs
June 21, 1701 Wrote Letter L-391 of 1701-06-21 to Hans Sloane about the claimed qualtity of other people's magnifying glasses, injuries to the cornea, and the impossibility of observing the smallest particles of matter
August 2, 1701 Wrote Letter L-392 of 1701-08-02 to the members of the Royal Society about circulation of blood in young eels and announcing his bequest of 26 magnifying glasses
August 26, 1701 Wrote Letter L-393 of 1701-08-26 to Frederik Adriaan van Reede about measuring the fall of water, an accurate instrument for such measurements, and his invention of a level
December 6, 1701 Wrote Letter L-397 of 1701-12-06 to Hans Sloane as a cover letter for Letter L-398 to John Somers
December 6, 1701 Wrote Letter L-398 of 1701-12-06 to John Somers about the sperm of young cocks living for days outside the cock and whether that was long enough to fertilise a hen's egg
December 20, 1701 Wrote Letter L-399 of 1701-12-20 to the members of the Royal Society about the sperm of spiders and how they copulate
February 9, 1702 Wrote Letter L-400 of 1702-02-09 to Hendrik van Bleyswijk about three types of little animals from the gutter of his house, one of which was eaten by a larger animal, which could revive after being dried out
February 14, 1702 Wrote Letter L-401 of 1702-02-14 to the members of the Royal Society about balsam, an apparatus he designed to inhale smoke and vapour, blood vessels in sheep lungs, his own phlegm, and the theory that cold air harms lungs
April 20, 1702 Wrote Letter L-403 of 1702-04-20 to Karl von Hessen-Kassel as a cover letter for Letter L-404
April 20, 1702 Wrote Letter L-404 of 1702-04-20 to Karl von Hessen-Kassel about silkworms, the structure of the silk thread, and the organs that produce it, eyes, pincers, blood vessels, and cocoons, sperm from an adult silk moth, and the scales on its wings