INTRODUCTION OF THE MICROSCOPE 8l 



he began to use the microscope is not known; his first pub- 

 lication in reference to microscopic objects did not appear 

 till 1673, when he was forty-one years old. 



His Microscopes. — He gave good descriptions and draw- 

 ings of his instruments, and those still in existence have been 

 described by Carpenter and others, and in consequence we 

 have a very good idea of his working equipment. During 

 his lifetime he sent as a present to the Royal Society of 

 London twenty-six microscopes, each provided with an object 

 to examine. Unfortunately, these were removed from the 

 rooms of the society and lost during the eighteenth century. 

 His lenses were of fine quality and were ground by himself. 

 They were nearly all simple lenses, of small size but con- 

 siderable curvature, and needed to be brought close to the 

 object examined. He had different microscopes for different 

 purposes, giving a range of magnifying powers from 40 to 270 

 diameters and possibly higher. The number of his lenses is 

 surprising; he possessed not less than 247 complete micro- 

 scopes, two of which were provided with double lenses, and 

 one with a triplet. In addition to the above, he had 172 

 lenses set between plates of metal, which give a total of 419 

 lenses used by him in his observations. Three were of 

 quartz, or rock crystal; the rest were of glass. More than 

 one-half the lenses were mounted in silver; three were in 

 gold. 



It is to be understood that all his microscopes were of 

 simple construction; no tubes, no mirror; simple pieces 

 of metal to hold the magnifying-glass and the objects to 

 be examined, with screws to adjust the position and the 

 focus. 



The three aspects of one of Leeuwenhoek's microscopes 



shown in Fig. 19 will give a very good idea of how they were 



constructed. These pictures represent the actual size of 



the instrument. The photographs were made by Professor 



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