I 1 8 THE HISTORY AND DEVELOPMENT OF THE MICROSCOPE 



sun's rays as a burning-glass, and that these were used to produce 

 ignition ; but there is no trace of suggestion that these refracting 

 globes could act as magnifying instruments. 



Seneca (* Qusest. Nat.' i. 6, 5) states, however, that ' letters 

 though small and indistinct are seen enlarged and more distinct- 

 through a globe of glass filled with water.' He also states that 

 * fruit appears larger when seen immersed in a vase of glass.' But 

 he only concludes from this that all objects seen through water 

 appear larger than they are. 



In like manner it could be shown that Archimedes, Ptolemy, 

 and others had no knowledge of the principles on which refraction 

 took place at curved surfaces. 



Nor is there any ancient mention of spectacles or other aids to 

 vision. Optical phenomena were treated of ; Aristotle and the Greek 

 physician Alexander dealt with myopy and presbyopy ; Plutarch 

 treated of myopy, and Pliny of the sight. But no allusion is made 

 to even the most simple optical aids ; nor is there any reference to 

 any such instruments by any Greek or Roman physician or author. 

 In the fifth century of the Christian era the Greek physician Actius 

 says that myopy is incurable; and similarly in the thirteenth 

 century another Greek physician, Actuarius, says that it is an in- 

 firmity of sight for which art can do nothing. But since the end of 

 the thirteenth century, which is after the invention of spectacles, 

 they are frequently referred to in medical treatises and other works. 



If we turn to the works of ancient artists we find amongst their 

 cut gems some works which reveal extreme minuteness of detail and 

 delicacy of execution, and some have contended that these could 

 only have been executed by means of lenses. But it is the opinion 

 of experts that there is no engraved work in our national collection 

 in the gem department that could not have been engraved by a 

 qualified modern engraver by means of unaided vision ; and in 

 reference to some very minute writing which it was stated by Pliny 

 that Cicero saw, Solinus and Plutarch, as well as Pliny, allude to these 

 marvels of workmanship for the purpose of proving that some men 

 are naturally endowed with powers of vision quite exceptional in 

 their excellence, no attempt being made to explain their minute 

 details as the result of using magnifying lenses. 



These and many other instances in which reference to lenses 

 must have been made had they existed or been known are con- 

 clusive ; for it is inconceivable that even simple dioptric lenses, to 

 say nothing of spectacles, microscopes and telescopes, could have 

 been known to the ancients without reference to them having been 

 made by many writers, and especially by such men as Galen and 

 Pliny. 



The earliest known reference to the invention of spectacles is 

 found in a manuscript dating from Florence in 1299, in which the 

 writer says, ' I find myself so pressed by age that I can neither 

 read nor write without those glasses they call spectacles, lately in- 

 vented, to the great advantage of poor old men when their sight 

 grows weak.' x Giordano da Rivalto in 1305 says that the invention 



1 Smith's Optics, Cambridge, 1738, 2 vols. ii. pp. 12, 13. 



