54 



mission to read the present paper, Sir William R. Hamilton 

 had kindly communicated to him the abstract and the proof 

 sheets of a memoir by Professor De Morg-an, on Triple Al- 

 gebra. That paper contains the discussion of a system of 

 triplets, which is most closely connected with the one now 

 proposed : the only difference being that Professor De Mor- 

 gan uses what are in fact new imaginary cube roots of negative 

 unity. 



Mr. Graves thinks that in the interpretation and generali- 

 zation of his results he has met with greater success ; but he 

 fully concedes to Professor De Morgan the prior possession 

 of what must be looked upon as fundamental in this theory, 

 the conception of symbols which act upon each other in the 

 same manner as the imaginary cube roots of unity. Mr. 

 Graves also stated that his brother, John T. Graves, Esq., 

 had anticipated him in the idea of using cube roots of positive 

 unity in the constitution of algebraic triplets. • 



The remaining portion of the paper, having reference 

 chiefly to the interpretation of the formulae obtained in the 

 multiplication of triplets, was postponed until the next meet- 

 ing of the Academy. 



Mr. George Yeates presented a tabular Return of the Ob- 

 servations made by him with Barometer, Thermometer, and 

 Rain Gauge, at his residence, near Portobello, County of 

 Dublin, during the year ending 31st December, 1844. — (See 

 Appendix, No. II.) 



DONATIONS. 



An Essay on Aerial Navigation. By Joseph M' Sweeny, 

 M, D. Presented by the Author. 



ArchcBologia, Vol. XXX,, and Index to Vols. XVI. to 

 XXX., inclusive. Presented by the Society of Antiquaries 

 of London. 



J. H. R. Mott's Advice and Instructions for playing the 



