Joblot, Louis

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Joblot, Louis

(b. Bar-le-Duc, Meuse, France, 9 August 1645; d. Paris, France, 27 April 1723)

microscopy, physics.

Joblot was the fourth of six children of Nicolas Joblot, Probably a moderately well-to-do; merchant, and Anne Guilly. The family was Roman Catholic.1 Nothing certain is known of Joblot’s life prior to his thirty-fifth year, and subsequent data are meager.2 He was probably educated at the Collége Gilles de Tréves founded at Bar-le-Duc in the second half of the sixteenth century. In 1680 he was appointed assistant professor of mathematics (geometry and perspective) at the école Nationale des Beaux-Arts, which was part of the Royal Academy of Painting and Sculpture. Neither this position nor the rank of academician associated with it was salaried, although Joblot was obliged to attend the meetings of the Academy. In 1697 Joblot obtained an eighteen-month Leave of absence to travel to Italy. Soon after his return, Sébastien le Clerc resigned his position as professor of mathematics and in May 1699 joblot succeeded him at a salary of 300 livers. During the summer of 1702 Joblot read to the Academy a series of lectures on optics and on the anatomy of the eye. In December 1716 he presented to the outline of his book on microscopy to the Academy, who decided to allow the book to be printed. Although the illustrations were ready at that time, this work was not completed until 1718. Joblot resigned his professorship on 26 April 1721 and died two years later at the age of seventy-seven.

It is probable that Joblot was led to his research on microscopy by the arrival in Pairs of Huygens and Hartsoeker in the summer of 1678. In July of that year, Huygens showed microscopes that he had brought from Holland and demonstrated infusoria before the Academy of Sciences. An account of this demonstration was published in the journal des sçavans (15 August 1678), which, two weeks later, published a description of Hartsoeker’s microscope.3 Probably inspired by these events, Joblot began his own research at about this time, and his Descriptions et usages de Plusieurs nouveaux microscopes makes particular reference to Hartsoeker’ visit and to his work on Infusoria.

The publication of Descriptions established Joblot as the first French microscopist. The first part of the book described several microscopes and their construction and introduced some improvements, including the use of stops (diaphragms) in compound microscopes to correct for chromatic aberration. Joblot designed the first porte loupe, a simple preparation microscope in which the lens is supported by a string of “Musschenbroek nuts,” forming a ball-and-socket jointed arm.

The second part of the book discusses Joblot’s microscopical observations. With the exception of his work on the vinegar-eels (nematodes), which dates from 1680,4 Joblot’s observations mainly concern Protozoa and were made between 1710 and 1716. Leeuwenhoek had observed the Protozoa previously,5 but Joblot’s is the earlist treatise on them. He described and illustrated a large number of new types and, according to Cole, was the first to observe the contractile vacuole, while Oudemans states that he was the first picture the larva of a hydrachnid6 and the nymph of Unioicola ypsilophorus, a parasite of the pond mussel.

Joblot believed that Infusoria originated from germs already present in the material from which the cold infusion was made or germs that were floating in the air. He proved his supposition by preparing two identical cold infusion of hay, one of which was shielded from the air: both developed Infusoria. In a similar experiment, but with infusion thaat had been boiling for fifteen minutes, the unshielded preparation developed Infusoria, while, even after a considerable time, the shielded one did not. When the latter infusion was exposed to the air, Infusoria developed. Because Joblot’use of sterilized infusions anticipated the later work of spallanzani and pasteur, he should be included, after Redi and Leeuwenhoek, in the list of investigatiors who disproved the doctrine of spontaneous generation.

In addition of mathematics (to which science he did not contribute) and microscopy, Joblet was interested in physics and espicially magnetism. He associated with Amontons and G. Homberg,7 the physicians J. Mery and Bourdelot and regularly attended meetings at the home of M. F. Geoffroy devoted to discussions of physics. In 1701 he constructed the first artificial magnet, using thin stripes of magnetized iron, an arrangement which is usually attributed to pierre Lemaire (1740).

Challenging the Cartesian theory of magnetism, Joblet formulated his own theory in which he denied, among other hypotheses, the existence of a dual flow of magnetic matter moving in oppposite directions; he maintained instead that only a single flow exists, a theory which sparked a contraversy with Puget. Further, Joblot refuted experimentally Descartes” ideas that with magnetic bars of equal weight and equal degree of magnetization, the longest will support the greatest weight. Although he is remembered for these contributions, Joblot”roles in the developement of magnetism has been insufficiently explored.


1. Afteran extensive search in the archives of Bar-le-Duc and surrounding communities, Konarski, Joblot”biographer, found only the name of Nicolas Joblot, with no mention of his profession or circumstances, The godparents of his children (allof whom were baptized in the church of the parish of Norte Dame) were either merchants or belonged to the upper classes of the city.

2. Most of the data are to be found in the minutes of the meetings of the Royal Academy of painting and sculpture.

3. This description was written by Huygens.

4. Leeuwenhoek described vinegar-eels two letters to H. Oldenburg. The first (11 Feb. 1675) was not published at the time; the second (9 Oct. 1676), in which more particulars _were given, was published in part in the Transactions of the Royal Society, 12 (1677), 821-831; and the Journal des scavans, 6 (1678), 106-110, 132-135. The obseervations; hence joblot”observations were probubly the first published. Leeuwenhoek”complete letter was published in The collected Ltters of antoni van Leeuwenhoek (Amsterdam, 1914), II 6-161.

5. Described in a letter to H. Oldenburg (7sept.1674) that was published in the Philosaphical Transactions of the Royal Society, 9 (1674), 178-182.

6. A curious picture (pl. 6 no.12) that resembles a human head.

7. Joblot (Descriptions . . ., II , 7) has Hombert, but this must be a printing error; no person by that name was a member of the French Academy.


I. Original Works.Joblot”works include“Lettre de M. Joblot, Professeur en mathematiques dans I ’.Academic Royale de peinture et Sculpture, a Paris, a Puget, a lyon” in Memoires pour servur ä histoire des sciences et des beayx- arts (July 1703); “Extrait d’ une nouvelle hypothese surI’Aiman”ibid.(Sept.1703);Descriptions et usages de plesieurs nouveaux microscopes, tant simples que composez;avec nouvaux observations faites sur une multitude innombrable d’insects d’autres animax de diverses espé qui naissent dans des liqueurs préparé & dans celles qui ne le sont point (Paris, 1718);2nd ed., enl and with entomological notes, Observations d’histoire naturelle faites avec le microscope surun grand nombred” insectes et sur les animalcules qui se trouvent dans les liqueurs . . .Avec la description et les usages des différens microscopes,2vols.(Paris, 1754-1755)

II. Secondary Litrature. An anonymous work concerning Joblot is “Description d’un aimant artificiel qui est dans le cabinet de M. Chamard”in Mémoí pour servir á I’ histoire des sciences et des beaux-arts (Nov.-Dec 1702). two very rare booklets by Puget, announced in journal des scavans (31 July 1702), are Letters écrites á un philosophe surle choix d’une hypothé se propre áexpliquer les effects d’un aimant (Lyons, 1702), and Lettre de M. Puget, de Lyon,á M. Joblot sur íaimant (Lyons 1702).

See also the following works (listed chronologically); Fontenelle, Histoire de l’Académie royale des sciences, annáe 1703 (Amsterdam ed., 1739), sec, 7, pp. 26-27; L. Lémery, “Diverses experiencs et observations chimiques et physiques sur le fer et l’aimant,” in Mémories de l’Académie royale des sciences, année 1706 (Amsterdam ed., 1708), pp. 148-169; J. M. Fleck, “Quels sont les premiers observateurs des infusoires?” in Mémories de l’Académie de Metz, 56 (3rd ser. 4 ) (1876), 651-652; P. Cazeneuve. “La génération spontanée d’après les liveres d’Henri Baker et de Joblot,” in Revue scientifique,31 (4th ser.1) (1894), 161-166; J. Boyer, “Joblot et Baker,” ibid., 283-284; W. Konarski, “Un savant barrisien, précurseur de M. Pasteur, Louis Joblot (1645-1723),” in Mémoires de la Société des letters sciences et arts, Bar-le-Duc,3rd ser., 4 (1895), 205-:333; H. Brocard, Louis de Pujit, FrançoisLamy, Louis Joblot, leur action scientifique d’après de nouveaux documents(Bar-le-Duc, 1905); C. Dobello, “A Protozoological Bicentenary, Antony van Leeuwenhoek (1632-1723) and Louis Joblot (1645-1723),” in Parasitology,15 (1923), 308-319; F. J. Cole, The History of Protozoology (London, 1926); A. C Oudemans, “Kritisch historisch overzicht der acarologie,” in Tijdschrift voor entomologie, 69 (1926), supp.; 72 (1929), supp.; and L. L. Woodruff, “Louis Joblot and the Protozoa,” in Scientific Monthly, 44 (1937), 41-47.

P. W. van der Pas