CHAPTER XXII 

 THE PAST AND FUTURE OF THE MICROSCOPE 



Earliest Inventions. — Convex glass lenses, used as specta- 

 cles for presbyopy, were made, according to the available 

 records, about 640 years ago. During the next 320 years 

 after this, the art of grinding and polishing low-power 

 convex lenses was more or less practiced, and at some 

 period concave lenses were also made. At any rate, one 

 of the first compound microscopes was that combination 

 of a convex objective lens with a concave eyelens, which 

 is now called a Bruecke magnifier, and which has been 

 lately abandoned because of its small field. This was 

 invented or re-invented by Galileo before 1620. About this 

 time came the use of a compound microscope of two convex 

 lenses, the discovery of which is doubtfully assigned to 

 various persons, and which was also used by Galileo. Of 

 course these lenses, being uncorrected, required to be 

 narrowly diaphragmed. Galileo appears to have used an 

 amplification of 36 times. It is difficult to distinguish 

 the original inventor, in those unscientific ages, from the 

 re-inventor, or from the person who made an instrument 

 from a report in a letter, or an indication carried by word 

 of mouth. Possibly some of the names that have come 

 down to us as original inventors at these distant periods 

 are the wrong ones. 



The Simple Magnifier. — Whoever may have invented 

 the compound microscope, however, it was destined to be 

 surpassed for about 200 years, in the work of microscopical 

 discovery, by the simple lens of short focus with a narrow 

 diaphragm. Practice in the grinding and mounting of 

 such small lenses enabled Leeuwenhoek, from 1673 

 onward, to chronicle such a list of microscopical discoveries 

 as hardly any other observer could claim. 



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