92 Obituary Notices of Felloivs deceased. 



where P is the central perpendicular on the tangent plane, and D is the 

 diameter drawn parallel to the element of the line of curvature. He also 

 gave some very valuable applications of the Calculus of Operations to the 

 Calculus of Variations, and especially arrived at a simple proof, by the 

 Operational Method, of Jacobi's celebrated theorem for distinguishing 

 between maxima and minima values in the application of the Calculus 

 of Variations to single integrals. 



On the death of Hamilton in 1865, Graves delivered from the 

 Presidential Chair of the Academy an eloquent eloge of that eminent 

 man, containing an interesting account of both his scientific labours 

 and of his literary attainments. 



Graves had much literary and artistic taste and cultivation, and to 

 these were, no doubt, largely due the symmetry and beauty both of 

 method and of results which are marked characteristics of his mathe- 

 matical work. 



As a member of the Academy, he devoted much time and thought 

 to antiquarian subjects in connection with Ireland. It is a striking 

 evidence of his versatility and varied accomplishments, that the 

 eminent antiquary, George Petrie, having died shortly after Graves 

 had paid the above recorded tribute to Hamilton's memory, he pro- 

 nounced a eloge on him also, and was able to give as clear and 

 competent a survey of the archaeological researches of the one as he had 

 done of the scientific investigations of the other. 



A subject which he studied with special zeal was that of the Ogham 

 inscriptions, so numerous in Ireland. He applied to the characters 

 employed in them the accepted methods for the decipherment of 

 writings, known or presumed to be alphabetical, and in this way con- 

 firmed the interpretation of these symbols which is given in some of the 

 old Irish books. He then proceeded to give readings and to prepare 

 renderings of a number of the actual inscriptions on cromlechs and 

 other stone monuments. The subject is still surrounded with difficul- 

 ties, and many archaeologists have been led to entertain the view that 

 the inscriptions, at least in some cases, are intentionally cryptic. 



Graves brought before Government, in a special publication, the 

 importance of having the old Irish laws, commonly called the Brehon 

 Laws, edited and translated by competent scholars. The suggestion 

 was adopted, and, when the project was taken in hand, he was ap- 

 pointed a member of the Commission charged with carrying it into 

 effect, and held this office till his death, which took place on July 17th, 

 1899. 



Graves was elected a Fellow of the Royal Society in 1880, and the 

 Honorary Degree of D.C.L. was conferred on him by the University 

 of Oxford in 1881. 



B. W. 



