THE PRESIDENTS ADDRESS. 117 



ing that Bacon possessed any especial knowledge of this subject, 

 while others affirm that if he did not himself reduce his attain- 

 ments to the actual formation and use of lenses, he made known 

 principles which could hardly remain long without practical appli- 

 cation. Some historians set down the year 1313 as the period 

 when spectacles were first invented, but in 1299 we find one writer 

 saying, " 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." Some authors set down the year 1214 as that in 

 which Friar Bacon invented spectacles, but leaving these doubtful 

 points, yon will see how from this time a steady onward pro- 

 gress is made in the application of the laws of Optics to the 

 amplification of distant and small objects. From the death of 

 Friar Bacon, in 1292, to the time of Maurolycus, about 1575, 

 philosophers seemed to have been principally occupied in investi- 

 gating the laws of refraction in their relations to glass and water, 

 apparently repeating and verifying the observations and calcula- 

 tions of Ptolemy. Franciscus Maurolycus, an eminent mathe- 

 matician of the 16th century, had advanced so far as to conceive 

 the true office of the crystalline lens of the eye, and published his 

 views in a work entitled " Theoremata de Lumine et Umbra," in 

 which he gives an explanation of the facts noticed years before by 

 Aristotle, that the rays from the sun passing into a dark room 

 through a minute hole always gave an image of the sun on a 

 screen placed at some little distance from it. About 15 years before 

 the publication of this work, Baptista Porta, then a youth, invented 

 the camera obscura, and Maurolycus being aware of the lens placed 

 to concentrate the light in this camera, was led to consider the 

 office of the crystalline lens to be analogous to it. All these 

 instances I have quoted show that men's minds were actively 

 exercised upon the subject of the refrangibility of the light-rays, 

 and were led gradually to the evolution of more complex apparatus 

 for the display of their phenomena. 



Those of you who visited the exhibition of scientific instruments 

 at the Loan Collection at South Kensington in 1876 may probably 

 remember Galileo's telescope. Galileo was born A.D. 1564, and 

 may be considered the founder of the microscope, inasmuch as 

 after inventing the telescope the invention of the microscope was 

 easy, the mathematical principles involved in their construction 



