1 1^4 Transactions of the Societij. 



ing and polishing lenses according to his method, but he refused 

 with much energy, saying that he did not think that many young 

 men would go through the necessary hard work in order to acquire 

 the proper skill. At his death nothing was found which threw 

 any light upon his method of work, upon the grinding of his lenses, 

 or upon his choice of material. AVhatever his methods were, he 

 found them out for himself, as there is no record of his having had 

 any nuister. The compound Microscope had been invented by the 

 Janssens before Leeuwenhoek began his work, but he always used 

 the simple jVIicroscope, which was probably preferable to the com- 

 pound Microscopes then in use. 



It is interesting in this connexion to remember that Charles 

 Darwin took no compound Microscope, but only a simple one with 

 him on his ' Beagle ' voyage ; he had a great liking for the simple 

 ^licroscope and some little distrust, even, of the compound. Leeu- 

 wcnhoek's Microscopes were indeed " the most simple possible," 

 as Baker says in his description of them. Martin Foulkes, in his 

 account of the twenty-six Microscopes left by T.eenwenhoek to the 

 Royal Society, from whose possession they and the " snuill Indian 

 cabinet " they were sent in have disappeared, says : '' They are all 

 single jVIicroscopes, consisting each of a very small double convex 

 glass, let into a socket between two silver plates, riveted together 

 and pierced with a small hole." He apparently knew the value of 

 a small diaphragm before a single lens, the reason and use of 

 which is so ably explained by Sir Ahnroth Wright in the section 

 o( his book dealing with the simple Microscope. Before the lens 

 was a movable pin on which to place or stick the object ; this 

 could be moved vertically and horizontally by screws, in order to 

 adjust the object to the line of vision ; and there was another screw 

 for focal adjustment. Baker also examined these twenty-six 

 ^licroscopes in 1740, seventeen years after IToulkes, and described 

 them in much the same words. He says: "These Microscopes 

 are plain and simple in their contrivance — all the parts are silver, 

 fashioned by ]\I. Leeuwenhoek's own hand, and the glasses, which 

 are excellent, were all ground and set by himself." 



As regards magnifying power, of these twenty-six Microscopes 

 one magnified 160 diameters, one 133, one 114, three 100, three 

 S9, eight 80, two 72, three 06, two 57, one 53, and one 40 : how 

 measured is not recorded. 



Foulkes savs : " The i]flasses are all exceedinolv clear, and show 

 the obiect verv brioht and distinct . . . beino all irround olasses, 

 none of them are so small, and consequently magnify to so great 

 a degree, as some of those drops, frequently used in other Micro- 

 scopes " ; but he says they were very much more distinct. In one 

 of his letters Leeuwenhoek says he had had many very small glasses 

 by him tor forty years, but he had made very little use of them, 

 as he found that the " most considerable discoveries were to be 



