580 SUMMARY OF CURRENT RESEARCHES RELATING TO 



erect ; not at an image now less and now greater than the object, but an 

 image always larger than the object from which it arises. 



Magini's observation could not therefore suggest to Galileo the idea 

 of a simple Microscope, for it was the very opposite of it, and further 

 because the simple Microscope was at that time (as will be shown) an 

 invention more than three centuries old. We see from this that the 

 good Abbe Eezzi must have been a most learned man, a man of letters, 

 but totally ignorant of the elements of optics, for we cannot suppose him 

 animated by the desire to deprive Galileo of the honour of having 

 invented the compound Microscope. 



As, however, amongst those not versed or badly versed in the sub- 

 jects and language of science, many may in good faith repeat the words 

 and arguments of Eezzi, thinkiag them correct, it is necessary to fully 

 understand the meaning of the expressions simple Microscojpe and com- 

 pound Microscope, so that in the future the like errors should not be 

 renewed. . . .* 



A single lens used to see, enlarged, the images of objects is called a 

 simple Microscope, but the same name is sometimes given, though 

 wrongly, to the ensemble of several lenses placed one over the other 

 provided they are close together or the intervals separating them are 

 very small relatively to the focus of each lens, because then the different 

 lenses act as if they were a single one of shorter focus than each 

 individual one. 



We call a compound Microscope one to form which several lenses 

 are used separated by considerable intervals, whether these lenses are of 

 the same or of different kinds, the lens on the side of the object being 

 called the objective, and the one next the eye the ocular. . . -t 



Having in such a way determined what is meant by simple Microscope 

 and compound Microscope, we must first of all find out to whom we owe 

 the invention of the simple Microscope. 



Although it results from a passage of Seneca (20) that the ancients 

 had noticed the apparent enlargement of objects seen through a spherical 

 glass vase full of water, yet the fact of there being no mention of lenses 

 in the Optics of Euclid, nor in those of Heliodorus of Larissa, nor in 

 Damian, nor in what remains of the Optics of Ptolemy, and what is 

 more, the reasons adduced with great erudition by Thomas Henri 

 Martin in his dissertation (21) sufficiently prove that the ancients had 

 no lenses properly so called, and that therefore they did not know 

 either simple or compound Microscopes. 



In spite of this it will not be inopportune to mention briefly here 

 the pretended concave emerald lens, which several writers, even very 

 recent ones, quoting Pliny, have supposed to have been used by Nero to 

 watch the fights of the gladiators. 



The celebrated naturalist of Como, speaking ' De diversitate 

 oculorum,' lib. xi. 53 et seq,, says first of all that " alii contuentur 

 longinqua, alii nisi prope admota non cernunt ; " then he adds a little 

 further that Nero's eyes were (ib,, 54) " nisi quum conniveret, ad prope 

 admota, hebetes," that is, that Nero's eyes were only able to see near 

 objects when he half closed them, or, in other words, Nero was a 

 myope, for half shutting the eyes or bringing the eyelids together is of 

 no use to long-sighted people to see objects near them, or even to look 



* A few paragraphs which deal with elementary points are omitted here, 

 t Ibid. 



