lo ELEMENTS OF APPLIED MICROSCOPY. 



edge, the first distinct advances were made in Arabia. 

 Alhazen, the great Arabian physician of the eleventh 

 century, distinctly describes the use of lenses for pro- 

 ducing enlarged images, in a publication supposed to 

 date from about 1052. Two centuries after, Roger 

 Bacon, the Franciscan monk, and noted alchemist, of 

 Oxford, noted the same effect. A little later, near the 

 end of the thirteenth century, lenses were first applied 

 to the mitigation of defects of vision; and to Salvino 

 d'Armato degli Armati, a Florentine, the invention of 

 spectacles is ascribed. The use of lenses as micrdscopes 

 for the examination of objects too minute to be studied 

 with the unaided eye became general about the end of 

 the sixteenth century. From the year 1600 such obser- 

 vations were numerous, and in 1637 the first diagram of 

 a microscope no~w extant was published by Descartes. 

 About 1665 small glass globules began to be used instead 

 of convex lenses for the simple microscope. They were 

 set in metal plates, on the side of which opposite to the 

 observer the object to be examined was mounted on some 

 sort of movable arm. With these instruments a high 

 magnification was obtainable; and it was with such 

 simple microscopes (Fig. 9) that the pioneer microscopists 

 of the seventeenth century, Kircher in Italy and Leeuwen- 

 hoek in Holland, founded the science of Micro- Biology. 

 8. The Compound Microscope. — Meanwhile a step 

 had been taken, which, though not particularly fruitful 

 at the time, was to become later of great significance. 

 This was the invention of the compound microscope 

 commonly attributed to the Dutch spectacle-makers. 



