132 Sir 0. B. Airy, Continuation of Observations on [March 10, 



March 10, 1884. 



Mr Glaisher, President, in the chair. 



D'Arcy W. Thompson, B.A., Trinity College, was elected a 

 Fellow. 



The following communications were made : 



(1) Continuation of Observations on the state of an Eye affected 

 with Astigmatism. By Sir George Biddell Airy, K.C.B., M.A., 

 LL.D., D.C.L., Honorary Fellow of Trinity College, Cambridge; 

 formerly Lucasian Professor and Plumian Professor in the Univer- 

 sity of Cambridge ; late Astronomer Eoyal. 



In making and treating the observations now presented to the 

 Cambridge Philosophical Society, I have used exactly the same 

 simple method which I have employed on four previous occasions, 

 and of which the details are preserved in the Transactions of the 

 Society. Without entering into further particulars, I now present 

 the immediate results of these observations, combined with those of 

 preceding examinations, in the same form as those which are 

 printed in Volume xii. Part I. of the Transactions. I have however 

 added the column of personal age, as bearing in some measure on 

 the explanation of the changes. 



I. Distance from the cornea of the left eye, at which a lumi- 

 nous point presents the appearance of a nearly horizontal line. 



Reciprocal = - 286. 



Difference -073 



In 1825, age 24, distance 35 inches 

 4-7 



5-4 

 5-6 

 5-95 



•213 

 •185 

 179 



•168 



-•028 

 -•006 

 -011 



II. Distance from the cornea of the left eye, at which a lumi- 

 nous point presents the appearance of a nearly vertical line. 



In 1825, age 24, distance 6 - inches; Reciprocal *166 



Difference —'054 



In 1846, ... 45, 89 ; \L12 



--018 



In 1866, ... 65, 10*6 ; '094 



+-006 



