LETTER 75. 16 SEPTEMBER 1692 249 
and I did all this in the way I’ve always done: and then 
I saw, with as great a wonderment as ever before, an 
unconceivably great number of little animalcules, and 
in so unbelievably small a quantity of the foresaid stuff, 
that those who didn’t see it with their own eyes could 
scarce credit it. These animalcules, or most all of them, 
moved so nimbly among one another, that the whole stuff 
seemed alive and a-moving. 
I again paid the strictest attention I possibly could to 
the bigness, or at any rate to the length, of the bodies of 
many of ’em'; but mostly to the little animalcules, which 
looked to me roundish. Afterwards, I took a grain of 
coarse sand (of the sort of sand that we use here in this 
country* for scouring the pewter, and other household 
chattels), and I stuck this sand-grain in front of the 
microscope through which I had seen the animalcules : 
and I am bound to say, after making careful measure- 
ments, which I did by eye, that the diameter of the sand- 
grain was above a thousand times longer than the diameter 
of one of the little animalcules which I saw in great 
numbers. Consequently, then, such a grain of sand was 
far more than a thousand millionfold bigger than one of 
the little creatures aforesaid. 
Besides, I also saw divers animalcules * whose bodies 
were a bit thicker than the little animals hereinbefore 
spoken of; but these were quite 5 or 6 times longer than 
they were thick, and therewithal their body was of equal 
thickness all along, so that I couldn’t make out which 
was their head, or which their tail end; all the more 
because when they were a-swimming, which they did 
very leisurely (and this was their only motion, with a 
little bending of the body now and then, as it seemed to 
me), they would go ahead first with one end of the body 
a 
1 de hoe grootheijt of de lengte van veele haar lighamen MS. . . . of 
wel de lengte van veele haar ’er lighamen Dutch printed version. 
2 alwaar hier te lande MS. waar mede hier te lande printed version. 
* Obviously bacilli of some sort, but otherwise unidentifiable. 
