ce 
60 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’ 
this Gentleman at Delft, he shew’d me several that indeed 
were very curious; but nothing more than what I had 
ordinarily seen before; being composed only of one single, 
very minute Glass-Sphere or Hemisphere,’ placed between 
two very thin pierced Laminae, or Plates of Brass, and 
the Object was brought to its due distance before the 
Glass by a fine Screw: But for his best sort, he beg’d our 
Excuse in concealing them. The Observations he has 
made with his Glasses are Printed in several Letters of 
his in Dutch ; but for the most part, they are to be found 
dispers’d in the Philosophical Transactions. 
There is a more illuminating reference to Leeuwenhoek in 
a letter written by Constantijn Huygens jun. to his brother 
Christiaan in the year of Molyneux’s visit: and as it illus- 
trates Leeuwenhoek’s extraordinary jealousy in guarding his 
microscopes, is may be quoted here. Constantijn junior, in 
this epistle, tells his brother that he has just seen one Willem 
Meester * (a skilled Dutch mechanic), who had recently been 
with the Landgrave of Hesse* to interview Leeuwenhoek. 
Says Constantijn : * 
He [Meester] had been with him [the Landgrave] to 
Leeuwenhoek’s, who wouldn’t show him any of his 
microscopes except those which he shows to everybody ; 
whereof the little glasses had, at least, a focal distance 
equal to the width of the back of a knife. And when the 
Landgrave had asked him whether he could obtain some, 
of his manufacture, he answered with much pride that he 
* This is an error: for L.’s glasses were neither spherical nor hemi- 
spherical, but ground biconvex lenses—as Thomas Molyneux correctly 
observed. 
* There are many other references to Meester in the Huygens corre- 
spondence. He appears to have accompanied the Prince of Orange in his 
campaigns. Cf. Huvr. Compl. de Chr. Huygens, Vol. VII, p. 439 note. 
* Karl, Landgrave of Hesse-Cassel (1654-1730), an amateur of science. 
* Printed in @uvr. Compl. de Chr. Huygens, Vol. 1X, p.38, No. 2408. 
5 Nov. 1685. The original MS. is in the Leyden Library, and is in 
French—from which I translate. Constantijn Huygens jun. (1628-1697) 
was elder brother of Christiaan (1629-1695), both being sons of Constantijn 
sen. (1596-1687). 
