LEEUWENHOEK’S MICROSCOPES 321 
on heavy writing-paper, while a pretty allegorical copper- 
plate engraving is placed at the beginning, along with 
another displaying Leeuwenhoek’s portrait. The text is 
in Dutch and Latin both. 
From this catalogue it appears that Leeuwenhoek left 
no less than 247 completely finished microscopes, each 
provided with a lens, and generally also with an object ; 
and, in addition to these, 172 lenses merely mounted 
between little plates—419 lenses in all, therefore. 
Among these lenses there are three made from so-called 
‘Amersfoort diamond” (rock-crystal pebble)*; and of 
one of the microscopes it is noted that its magnifying- 
glass is ground from a sand-grain, while the object placed 
before it is likewise a sand-grain. ‘T'wo microscopes are 
specified as having two glasses, another three. It thus 
appears that Leeuwenhoek also manufactured doublets 
and triplets”; for, with his kind of apparatus, there can 
obviously be no question of any proper compound micro- 
scope. More than half of these microscopes (approxi- 
mately 160) were mounted in silver. Among the rest 
there are three made of gold—two of which weighed 
10 engels* 17 grains, the third 10 engels 14 grains. One 
of the former was sold for 23 florins 15 stivers, while both 
the others were bought in. (This is probably the only 
occasion on which microscopes have been sold by weight.) 
The remaining microscopes were sold in pairs. The brass 
ones fetched 15 stivers to 3 florins a pair, the silver 2 to 7 
florins. The entire sale realized a sum of 737 florins and 
3 stivers.t The names of the buyers show that all these 
i.e. quartz. I know of no evidence to show that L. ever made 
lenses from real diamonds—as is sometimes stated (e.g. by Nordenskidld, 
1929 ; p. 165). 
2 It now seems more probable that these were really double (or triple) 
simple microscopes—i.e. 2 (or 3) single lenses mounted in the same frame 
side by side—like the “double microscope” illustrated by Haaxman (1875) 
p. 34, fig. 2A. 
* An engels equals 32 grains: see p. 338 infra. 
* About £61. 10s. in modern English currency. 
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