The Natural Philosopher and the Microscope: Nicolas Hartsoeker Unravels Nature's “Admirable Œconomy”:

In a 1 685 letter to his younger brother Christiaan, Constantijn Huygens wrote, "How can a garcon like him who hardly knows any mathematics and hasn't had a masterteacher [maistre] set himself up as the first master of everybody?"1 The 'boy' in question was the twenty-nine-year-old Nicolas Hartsoeker2 (1656-1727). Constantijn seemed indignant at the news that "the same Hartsoecker who taught us how to make the small bead lenses for microscopes" had now mastered the art of making very large telescope lenses.3 There was more to Constantijn's sarcastic tone, however. From the letter exchange between the Huygens brothers, we learn that the young lens maker had been missing in action for a long time. Since September 1679, the brothers had not heard anything from him directly. And this after Huygens played a crucial role in taking Hartsoeker with him to Paris and introducing his younger compatriot to the French Academy of Sciences.4 Aware of his brother's help in launching Hartsoeker's career, Constantijn seemed indignant about Hartsoeker's silence. "I beg you to write to Paris as soon as possible to find out all the details. You could even write to Hartsoeker himself, provided that he doesn't disdain corresponding with poor people like us", harrumphed Constantijn. "If his lenses are as perfect as they should be", he continued, "you will see that this man will soon be sought after by some great patron. . .". But how could a garcon like Hartsoeker have become "such a great [lens grinding] master on the sly"?5 This is a striking remark from Constantijn, who in a letter to his brother Christiaan once called Hartsoeker "the inventor of our microscopes".6 This episode reveals yet another key element here. Both Christiaan and Constantijn Huygens were avid lens grinders, who much of the time discussed techniques, instruments and new strategies in applied optics. Therefore, both were interested in lens-related novelties and gifted lens makers who were few and far between. Hartsoeker was one of these young and skilled lens makers.In this article, I explore Nicolas Hartsoeker's role as instrument maker and his use of materials and tools in launching his own natural philosophical programme. His lens grinding talents got the attention of Christiaan Huygens (1629-95) and Giovanni Domenico Cassini (1625-1712) at the Academie who invited him to work there. At the Parisian Academy, Hartsoeker supervised the production of glassware for all the scientific instruments destined for the Jesuit missionaries in Siam and India.7 His skills earned him a job at the Academy's Observatory, for which he made telescopic lenses.8 He ground lenses, invented new lens-making machines, conducted chymical experiments with burning mirrors, magnetized needles and metal bars, dissected animal parts, and observed the behaviour of spermatozoa. Gradually, he also tried to establish himself as a natural philosopher and author of a system of physics at the Academy of Sciences in Paris. In 1699 he earned the title of foreign associate of the Academy9 Hartsoeker occupied a labile position as both instrument maker and philosophe; hence the light he can shine on the role of instruments in his natural philosophical works deserves attention. How did his natural philosophy inform his artisanal practice as a lens grinder and, vice versa, how did his artisanal occupations infiltrate his philosophical investigations? Moreover, how did his thinking about the use and utility of instruments like the microscope change over the course of his life? What kind of certainty did he accord to the microscope? Ultimately, what role did instruments play in how he gained knowledge about the natural world? This examination is not meant to separate the theoretical from the empirical spheres artificially. Instead, it will reveal how closely the two spheres were intertwined and how Hartsoeker used them.MICROSCOPY IN THE DUTCH REPUBLIC AND BEYONDThe Parisian and Dutch contexts colour the background of Hartsoeker's story, in which he and his contemporaries were grappling with the principles and research methods set forth in Descartes's mechanical philosophy. …