Dr. Charles Singer presented the following paper on 

 '' The Earliest Steps in the Invention of the Microscope." 

 The paper was taken as read. 



THE EARLIEST STEPS IN THE INVENTION OF THE 

 MICROSCOPE. 



By Charles Singer, M.A., M.D.Oxford, F.R.C.P.Lond., F.S.A. 



The microscopes and the microscopic work of the classical 

 observers, Leeuwenhoek, Malpighi, Hooke, and Kircher, have been 

 frequently described and figured. These descriptions are readily- 

 accessible, and I shall therefore confine myself to the earliest stages 

 in the discovery of the microscope, which is, of course, intimately 

 connected with the invention of the telescope. About these early 

 stages vague statements are often made, but the actual data do 

 not seem to have been put together. 



(1) Eiirlid (third century, B.C.), in his Optics, considered that 

 light passed in straight lines, and regarded an object seen as formed 

 by a cone with its base at the object and the apex at the eye. The 

 Euclidian origin of this work is disputed by some, who hold that 

 is is by Theon of Alexandria, who lived in the fourth century, A.D., 

 and was perhaps the father of Hypatia. The most recent edition is 

 by G. Ovio, UOttica di Euclide, Milan, 1918. 



(2) Ptolemy (died about 155 A.D.), in his Optics, began the 

 study of refraction, and applied the experimental method to this 

 subject. He showed that luminous rays, in passing from one 

 medium to another are deflected, and he attempted to measure the 

 deflection. This work of Ptolemy was written in Greek, and has 

 been lost. It was translated from Greek into Arabic, and, in the 

 twelfth century, from Arabic into Latin. Only the Latin version 

 survives, and its attribution to Ptolemy is doubtful. The best 

 edition is by G. Govi, Turin. 



(3) Alhazen (Abu Ali Al-Hazan Ibn Alhasan, 965-1038), was 

 an Arab of Basra, who abstracted the work of the older Greek 

 optical writers. He devoted much space and skill to the develop- 

 ment of the effects of curved mirrors. He had a fairly clear notion 

 of the nature of refraction, and improved the apparatus of Ptolemy 

 for measuring the angle of refraction in different media. He had 



